<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://www.veracyte.com/role/A401KPlan" xlink:href="vcyt-20161231.xsd#A401KPlan" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/A401KPlanDetails" xlink:href="vcyt-20161231.xsd#A401KPlanDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/BalanceSheetComponents" xlink:href="vcyt-20161231.xsd#BalanceSheetComponents" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/BalanceSheetComponentsAccruedLiabilitiesDetails" xlink:href="vcyt-20161231.xsd#BalanceSheetComponentsAccruedLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/BalanceSheetComponentsPropertyAndEquipmentNetDetails" xlink:href="vcyt-20161231.xsd#BalanceSheetComponentsPropertyAndEquipmentNetDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/BalanceSheetComponentsTables" xlink:href="vcyt-20161231.xsd#BalanceSheetComponentsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/BalanceSheets" xlink:href="vcyt-20161231.xsd#BalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/BalanceSheetsParenthetical" xlink:href="vcyt-20161231.xsd#BalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/BusinessCombination" xlink:href="vcyt-20161231.xsd#BusinessCombination" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/BusinessCombinationDetails" xlink:href="vcyt-20161231.xsd#BusinessCombinationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/BusinessCombinationTables" xlink:href="vcyt-20161231.xsd#BusinessCombinationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/CommitmentsAndContingencies" xlink:href="vcyt-20161231.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/CommitmentsAndContingenciesCapitalLeaseDetails" xlink:href="vcyt-20161231.xsd#CommitmentsAndContingenciesCapitalLeaseDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/CommitmentsAndContingenciesDetails" xlink:href="vcyt-20161231.xsd#CommitmentsAndContingenciesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/CommitmentsAndContingenciesTables" xlink:href="vcyt-20161231.xsd#CommitmentsAndContingenciesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/Debt" xlink:href="vcyt-20161231.xsd#Debt" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/DebtCreditAgreementDetails" xlink:href="vcyt-20161231.xsd#DebtCreditAgreementDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/DebtCreditAgreementTabularDetails" xlink:href="vcyt-20161231.xsd#DebtCreditAgreementTabularDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/DebtLoanAndSecurityAgreementDetails" xlink:href="vcyt-20161231.xsd#DebtLoanAndSecurityAgreementDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/DebtLoanAndSecurityAgreementTabularDetails" xlink:href="vcyt-20161231.xsd#DebtLoanAndSecurityAgreementTabularDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/DebtTables" xlink:href="vcyt-20161231.xsd#DebtTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/DocumentAndEntityInformation" xlink:href="vcyt-20161231.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/FairValueMeasurements" xlink:href="vcyt-20161231.xsd#FairValueMeasurements" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/FairValueMeasurementsDetails" xlink:href="vcyt-20161231.xsd#FairValueMeasurementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/GenzymeCoPromotionAgreement" xlink:href="vcyt-20161231.xsd#GenzymeCoPromotionAgreement" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/GenzymeCoPromotionAgreementDetails" xlink:href="vcyt-20161231.xsd#GenzymeCoPromotionAgreementDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/IncomeTaxes" xlink:href="vcyt-20161231.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/IncomeTaxesIncomeTaxExaminationDetails" xlink:href="vcyt-20161231.xsd#IncomeTaxesIncomeTaxExaminationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/IncomeTaxesTables" xlink:href="vcyt-20161231.xsd#IncomeTaxesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/IncomeTaxesTaxEffectsDetails" xlink:href="vcyt-20161231.xsd#IncomeTaxesTaxEffectsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails" xlink:href="vcyt-20161231.xsd#IncomeTaxesUnrecognizedTaxBenefitsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/InterestExpenseDetails" xlink:href="vcyt-20161231.xsd#InterestExpenseDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/NetLossPerShare" xlink:href="vcyt-20161231.xsd#NetLossPerShare" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/NetLossPerShareDetails" xlink:href="vcyt-20161231.xsd#NetLossPerShareDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/NetLossPerShareTables" xlink:href="vcyt-20161231.xsd#NetLossPerShareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/OrganizationAndDescriptionOfBusiness" xlink:href="vcyt-20161231.xsd#OrganizationAndDescriptionOfBusiness" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/SelectedQuarterlyFinancialDataUnaudited" xlink:href="vcyt-20161231.xsd#SelectedQuarterlyFinancialDataUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/SelectedQuarterlyFinancialDataUnauditedDetails" xlink:href="vcyt-20161231.xsd#SelectedQuarterlyFinancialDataUnauditedDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/SelectedQuarterlyFinancialDataUnauditedTables" xlink:href="vcyt-20161231.xsd#SelectedQuarterlyFinancialDataUnauditedTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StatementsOfCashFlows" xlink:href="vcyt-20161231.xsd#StatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StatementsOfOperationsAndComprehensiveLoss" xlink:href="vcyt-20161231.xsd#StatementsOfOperationsAndComprehensiveLoss" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StatementsOfStockholdersEquity" xlink:href="vcyt-20161231.xsd#StatementsOfStockholdersEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StockIncentivePlans" xlink:href="vcyt-20161231.xsd#StockIncentivePlans" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StockIncentivePlansActivityUnderStockOptionPlansDetails" xlink:href="vcyt-20161231.xsd#StockIncentivePlansActivityUnderStockOptionPlansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StockIncentivePlansAdditionalInformationDetails" xlink:href="vcyt-20161231.xsd#StockIncentivePlansAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StockIncentivePlansStockBasedCompensationDetails" xlink:href="vcyt-20161231.xsd#StockIncentivePlansStockBasedCompensationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StockIncentivePlansStockIncentivePlansEsppDetails" xlink:href="vcyt-20161231.xsd#StockIncentivePlansStockIncentivePlansEsppDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StockIncentivePlansStockOptionPlansDetails" xlink:href="vcyt-20161231.xsd#StockIncentivePlansStockOptionPlansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StockIncentivePlansTables" xlink:href="vcyt-20161231.xsd#StockIncentivePlansTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StockholdersEquityDeficit" xlink:href="vcyt-20161231.xsd#StockholdersEquityDeficit" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StockholdersEquityDeficitTables" xlink:href="vcyt-20161231.xsd#StockholdersEquityDeficitTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/StockholdersEquityDetails" xlink:href="vcyt-20161231.xsd#StockholdersEquityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/SummaryOfSignificantAccountingPolicies" xlink:href="vcyt-20161231.xsd#SummaryOfSignificantAccountingPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/SummaryOfSignificantAccountingPoliciesCreditRiskRestrictedCashAndAllowanceForDoubtfulAccountsDetails" xlink:href="vcyt-20161231.xsd#SummaryOfSignificantAccountingPoliciesCreditRiskRestrictedCashAndAllowanceForDoubtfulAccountsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/SummaryOfSignificantAccountingPoliciesIntangibleAssetsBonusAccrualsAndRevenueRecongitionDetails" xlink:href="vcyt-20161231.xsd#SummaryOfSignificantAccountingPoliciesIntangibleAssetsBonusAccrualsAndRevenueRecongitionDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/SummaryOfSignificantAccountingPoliciesLiquidityDetails" xlink:href="vcyt-20161231.xsd#SummaryOfSignificantAccountingPoliciesLiquidityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:href="vcyt-20161231.xsd#SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:href="vcyt-20161231.xsd#SummaryOfSignificantAccountingPoliciesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/ThyroidCytopathologyPartners" xlink:href="vcyt-20161231.xsd#ThyroidCytopathologyPartners" xlink:type="simple" />
  <link:roleRef roleURI="http://www.veracyte.com/role/ThyroidCytopathologyPartnersDetails" xlink:href="vcyt-20161231.xsd#ThyroidCytopathologyPartnersDetails" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/A401KPlan" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/A401KPlanDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/BalanceSheetComponents" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/BalanceSheetComponentsAccruedLiabilitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/BalanceSheetComponentsPropertyAndEquipmentNetDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_B923924C3E34158F06B66C7AC948F248" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_80D342AA6D8BCE940D686C7AC94803CE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_B923924C3E34158F06B66C7AC948F248" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_80D342AA6D8BCE940D686C7AC94803CE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_F974A659CB3CD5C029876C7AC948669D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_80D342AA6D8BCE940D686C7AC94803CE" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_F974A659CB3CD5C029876C7AC948669D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3633F7FF9BB2EB6D26836C7AC9485520_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_F974A659CB3CD5C029876C7AC948669D" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3633F7FF9BB2EB6D26836C7AC9485520_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3633F7FF9BB2EB6D26836C7AC9485520" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_F974A659CB3CD5C029876C7AC948669D" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3633F7FF9BB2EB6D26836C7AC9485520" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_6F484F64877CA78E11106C7AC948B1A9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3633F7FF9BB2EB6D26836C7AC9485520" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_6F484F64877CA78E11106C7AC948B1A9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquipmentMember" xlink:label="loc_us-gaap_EquipmentMember_E75266855CE968EA0E316C7AC948F6CD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3633F7FF9BB2EB6D26836C7AC9485520" xlink:to="loc_us-gaap_EquipmentMember_E75266855CE968EA0E316C7AC948F6CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ComputerEquipmentMember" xlink:label="loc_us-gaap_ComputerEquipmentMember_183A276AFA9F82042E156C7AC948170B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3633F7FF9BB2EB6D26836C7AC9485520" xlink:to="loc_us-gaap_ComputerEquipmentMember_183A276AFA9F82042E156C7AC948170B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember" xlink:label="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_179B5FB3C01BC00F1FC66C7AC9481C68" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3633F7FF9BB2EB6D26836C7AC9485520" xlink:to="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_179B5FB3C01BC00F1FC66C7AC9481C68" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FurnitureAndFixturesMember" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_AC5A1945C5C859F37D506C7AC9482E12" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3633F7FF9BB2EB6D26836C7AC9485520" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_AC5A1945C5C859F37D506C7AC9482E12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConstructionInProgressMember" xlink:label="loc_us-gaap_ConstructionInProgressMember_E965FD5FB52D10A8DB576C7AC9485305" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3633F7FF9BB2EB6D26836C7AC9485520" xlink:to="loc_us-gaap_ConstructionInProgressMember_E965FD5FB52D10A8DB576C7AC9485305" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_2D5056CEEE7EB40D8B7D6C7AC949C113" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_B923924C3E34158F06B66C7AC948F248" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_2D5056CEEE7EB40D8B7D6C7AC949C113" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_6D1F8E86D1F2BFEB7E8A6C7AC9492948" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_B923924C3E34158F06B66C7AC948F248" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_6D1F8E86D1F2BFEB7E8A6C7AC9492948" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_EB9C233BB0BB1CC23AAC6C7AC949F415" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_B923924C3E34158F06B66C7AC948F248" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_EB9C233BB0BB1CC23AAC6C7AC949F415" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_70A769DFB76621E403066C7AC949EA62" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_B923924C3E34158F06B66C7AC948F248" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_70A769DFB76621E403066C7AC949EA62" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DepreciationandAmortizationExpense" xlink:label="loc_vcyt_DepreciationandAmortizationExpense_C0EFF154BC9C0342E29E6C7ACBAFBC04" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_B923924C3E34158F06B66C7AC948F248" xlink:to="loc_vcyt_DepreciationandAmortizationExpense_C0EFF154BC9C0342E29E6C7ACBAFBC04" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/BalanceSheetComponentsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/BalanceSheets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/BalanceSheetsParenthetical" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/BusinessCombination" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/BusinessCombinationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_CA08E33EF3F246550FE96C7AFA732C08" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_CA08E33EF3F246550FE96C7AFA732C08" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_A71DB84CE53ECBC065C06C7AFA7354E9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_CA08E33EF3F246550FE96C7AFA732C08" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_A71DB84CE53ECBC065C06C7AFA7354E9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_AA112A174B8B0B22298C6C7AFA736F69_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_A71DB84CE53ECBC065C06C7AFA7354E9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_AA112A174B8B0B22298C6C7AFA736F69_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_AA112A174B8B0B22298C6C7AFA736F69" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_A71DB84CE53ECBC065C06C7AFA7354E9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_AA112A174B8B0B22298C6C7AFA736F69" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_AllegroDiagnosticsCorpMember" xlink:label="loc_vcyt_AllegroDiagnosticsCorpMember_2D5A50CE4AEDB7251C536C7AFA733132" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_AA112A174B8B0B22298C6C7AFA736F69" xlink:to="loc_vcyt_AllegroDiagnosticsCorpMember_2D5A50CE4AEDB7251C536C7AFA733132" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_03336DEDC350B225BFD26C7AFA734D32" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_CA08E33EF3F246550FE96C7AFA732C08" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_03336DEDC350B225BFD26C7AFA734D32" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_A20AD2AEA75DEC5EE8BB6C7AFA738BA7_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_03336DEDC350B225BFD26C7AFA734D32" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_A20AD2AEA75DEC5EE8BB6C7AFA738BA7_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_A20AD2AEA75DEC5EE8BB6C7AFA738BA7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_03336DEDC350B225BFD26C7AFA734D32" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_A20AD2AEA75DEC5EE8BB6C7AFA738BA7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InProcessResearchAndDevelopmentMember" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_D4F70774D86623340CB96C7AFA73C6F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_A20AD2AEA75DEC5EE8BB6C7AFA738BA7" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_D4F70774D86623340CB96C7AFA73C6F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NonrecurringAdjustmentAxis" xlink:label="loc_us-gaap_NonrecurringAdjustmentAxis_CFB1253C06F489EB0D5F6C7AFA7337D9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_CA08E33EF3F246550FE96C7AFA732C08" xlink:to="loc_us-gaap_NonrecurringAdjustmentAxis_CFB1253C06F489EB0D5F6C7AFA7337D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NonrecurringAdjustmentDomain" xlink:label="loc_us-gaap_NonrecurringAdjustmentDomain_6396DED065BD01D881E76C7AFA733582_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_NonrecurringAdjustmentAxis_CFB1253C06F489EB0D5F6C7AFA7337D9" xlink:to="loc_us-gaap_NonrecurringAdjustmentDomain_6396DED065BD01D881E76C7AFA733582_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NonrecurringAdjustmentDomain" xlink:label="loc_us-gaap_NonrecurringAdjustmentDomain_6396DED065BD01D881E76C7AFA733582" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_NonrecurringAdjustmentAxis_CFB1253C06F489EB0D5F6C7AFA7337D9" xlink:to="loc_us-gaap_NonrecurringAdjustmentDomain_6396DED065BD01D881E76C7AFA733582" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TransactionBonusesOtherPaymentsToEmployeesAndAcquisitionRelatedExpensesMember" xlink:label="loc_vcyt_TransactionBonusesOtherPaymentsToEmployeesAndAcquisitionRelatedExpensesMember_B5031BE4A35DA62E7FD06C7AFA735F5F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonrecurringAdjustmentDomain_6396DED065BD01D881E76C7AFA733582" xlink:to="loc_vcyt_TransactionBonusesOtherPaymentsToEmployeesAndAcquisitionRelatedExpensesMember_B5031BE4A35DA62E7FD06C7AFA735F5F" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_InterestExpenseRelatedToIndebtednessOfAcquiredEntityMember" xlink:label="loc_vcyt_InterestExpenseRelatedToIndebtednessOfAcquiredEntityMember_7C9207E51CEBFC7401C96C7AFA73F2CA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonrecurringAdjustmentDomain_6396DED065BD01D881E76C7AFA733582" xlink:to="loc_vcyt_InterestExpenseRelatedToIndebtednessOfAcquiredEntityMember_7C9207E51CEBFC7401C96C7AFA73F2CA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_446687AA8CBFFFB9270D6C7AFA730ECE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_CA08E33EF3F246550FE96C7AFA732C08" xlink:to="loc_us-gaap_RangeAxis_446687AA8CBFFFB9270D6C7AFA730ECE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_115AF3EADF08504C1E1A6C7AFA73A5DF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_446687AA8CBFFFB9270D6C7AFA730ECE" xlink:to="loc_us-gaap_RangeMember_115AF3EADF08504C1E1A6C7AFA73A5DF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_115AF3EADF08504C1E1A6C7AFA73A5DF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_446687AA8CBFFFB9270D6C7AFA730ECE" xlink:to="loc_us-gaap_RangeMember_115AF3EADF08504C1E1A6C7AFA73A5DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_D24BADD516841B1D90946C7AFA738636" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_115AF3EADF08504C1E1A6C7AFA73A5DF" xlink:to="loc_us-gaap_MaximumMember_D24BADD516841B1D90946C7AFA738636" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_BusinessAcquisitionNumberOfSharesReceivedForEachSubsidiaryShare" xlink:label="loc_vcyt_BusinessAcquisitionNumberOfSharesReceivedForEachSubsidiaryShare_FAA542BCE4FFB504E1D26C7AFA74FC0A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:to="loc_vcyt_BusinessAcquisitionNumberOfSharesReceivedForEachSubsidiaryShare_FAA542BCE4FFB504E1D26C7AFA74FC0A" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_BusinessAcquisitionRightToReceiveUponCancellationOfPreferredStockNumberOfShares" xlink:label="loc_vcyt_BusinessAcquisitionRightToReceiveUponCancellationOfPreferredStockNumberOfShares_0653BF761A5E4F85F92A6C7AFA745A6E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:to="loc_vcyt_BusinessAcquisitionRightToReceiveUponCancellationOfPreferredStockNumberOfShares_0653BF761A5E4F85F92A6C7AFA745A6E" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_BusinessAcquisitionRightToReceiveUponCancellationOfPreferredStockCash" xlink:label="loc_vcyt_BusinessAcquisitionRightToReceiveUponCancellationOfPreferredStockCash_3C2D73559595E747C5186C7AFA744D68" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:to="loc_vcyt_BusinessAcquisitionRightToReceiveUponCancellationOfPreferredStockCash_3C2D73559595E747C5186C7AFA744D68" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_PaymentsToAcquireBusinessesSettlementOfLiabilitiesIncurred" xlink:label="loc_vcyt_PaymentsToAcquireBusinessesSettlementOfLiabilitiesIncurred_0A3190AFCB983DBC46066C7AFA741FE8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:to="loc_vcyt_PaymentsToAcquireBusinessesSettlementOfLiabilitiesIncurred_0A3190AFCB983DBC46066C7AFA741FE8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts" xlink:label="loc_us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts_A6A3780AD427F5CFD8276C7AFA744E48" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:to="loc_us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts_A6A3780AD427F5CFD8276C7AFA744E48" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessCombinationIntegrationRelatedCosts" xlink:label="loc_us-gaap_BusinessCombinationIntegrationRelatedCosts_8D3772729DAECA251DF96C7AFA743855" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:to="loc_us-gaap_BusinessCombinationIntegrationRelatedCosts_8D3772729DAECA251DF96C7AFA743855" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredAbstract" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1141838B5823376090776C7AFA74B5CD" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1141838B5823376090776C7AFA74B5CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_D96F50D51248F0E06F9D6C7AFA748AC9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1141838B5823376090776C7AFA74B5CD" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_D96F50D51248F0E06F9D6C7AFA748AC9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_665A16E76F2159EF14A06C7AFA7448E0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1141838B5823376090776C7AFA74B5CD" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_665A16E76F2159EF14A06C7AFA7448E0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_60B10E0786229C116EA46C7AFA748CCB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1141838B5823376090776C7AFA74B5CD" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_60B10E0786229C116EA46C7AFA748CCB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_EEAF81CAA5C782D519406C7AFA742845" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1141838B5823376090776C7AFA74B5CD" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_EEAF81CAA5C782D519406C7AFA742845" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionSharePrice" xlink:label="loc_us-gaap_BusinessAcquisitionSharePrice_192BD36F05654B13BCDD6C7AFA74D548" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1141838B5823376090776C7AFA74B5CD" xlink:to="loc_us-gaap_BusinessAcquisitionSharePrice_192BD36F05654B13BCDD6C7AFA74D548" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_B8A5253D2FEA5094BFFD6C7AFA74DDCE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_B8A5253D2FEA5094BFFD6C7AFA74DDCE" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsOther" xlink:label="loc_vcyt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsOther_10944A53583D7EC05A3F6C7AFA74CE76" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_vcyt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsOther_10944A53583D7EC05A3F6C7AFA74CE76" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInProcessResearchAndDevelopment" xlink:label="loc_vcyt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInProcessResearchAndDevelopment_AD41078F801A5BC323246C7AFA7533EB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_vcyt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInProcessResearchAndDevelopment_AD41078F801A5BC323246C7AFA7533EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_1C74A786CA96C487E49C6C7AFA75AABF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_us-gaap_Goodwill_1C74A786CA96C487E49C6C7AFA75AABF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_957A99292C6FB4C3F70A6C7AFA755CFC" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_957A99292C6FB4C3F70A6C7AFA755CFC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueInputsDiscountRate" xlink:label="loc_us-gaap_FairValueInputsDiscountRate_3BA62B1B2AEE051C9ABD6C7AFA75E635" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_us-gaap_FairValueInputsDiscountRate_3BA62B1B2AEE051C9ABD6C7AFA75E635" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_2F9D70CB97EA0122B3106C7AFA75AF61" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_2F9D70CB97EA0122B3106C7AFA75AF61" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_9020E919202C1C32AE0A6C7AFA750710" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_9020E919202C1C32AE0A6C7AFA750710" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_954C87F634BE50CE37466C7AFA75B0FB" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_954C87F634BE50CE37466C7AFA75B0FB" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_FiniteLivedIntangibleAssetsAnnualAmortizationExpense" xlink:label="loc_vcyt_FiniteLivedIntangibleAssetsAnnualAmortizationExpense_534D545050CD63A1C7436C7AFA751592" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_vcyt_FiniteLivedIntangibleAssetsAnnualAmortizationExpense_534D545050CD63A1C7436C7AFA751592" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_FiniteLivedIntangibleAssetsAnnualAmortizationExpenseNextFiveYears" xlink:label="loc_vcyt_FiniteLivedIntangibleAssetsAnnualAmortizationExpenseNextFiveYears_0C719ECABE4892B51CCF6C7AFA758E65" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_D0EE047A7E25A2502BCD6C7AFA74A47D" xlink:to="loc_vcyt_FiniteLivedIntangibleAssetsAnnualAmortizationExpenseNextFiveYears_0C719ECABE4892B51CCF6C7AFA758E65" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionProFormaInformationAbstract" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaInformationAbstract_556E4837EF90F0763EBD6C7AFA754976" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_082BB7B8022AEF9D73876C7AFA74939F" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaInformationAbstract_556E4837EF90F0763EBD6C7AFA754976" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionsProFormaRevenue" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_B4B6F3A61D94DDE9290B6C7AFA750344" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionProFormaInformationAbstract_556E4837EF90F0763EBD6C7AFA754976" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_B4B6F3A61D94DDE9290B6C7AFA750344" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_1836EC18554894CA478D6C7AFA750F83" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionProFormaInformationAbstract_556E4837EF90F0763EBD6C7AFA754976" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_1836EC18554894CA478D6C7AFA750F83" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_865E6C5163526C4FD3CA6C7AFA750973" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionProFormaInformationAbstract_556E4837EF90F0763EBD6C7AFA754976" xlink:to="loc_us-gaap_ProfitLoss_865E6C5163526C4FD3CA6C7AFA750973" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/BusinessCombinationTables" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_2FE3EC371DCF7A4D79AD888CE4A56C4B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5A647C2D8CABF370216A888CE4A5DD94" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2FE3EC371DCF7A4D79AD888CE4A56C4B" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5A647C2D8CABF370216A888CE4A5DD94" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_304DB547E50BBDA839E7888CE4A592BB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5A647C2D8CABF370216A888CE4A5DD94" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_304DB547E50BBDA839E7888CE4A592BB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0497EE70D0142093A295888CE4A507B4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_304DB547E50BBDA839E7888CE4A592BB" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0497EE70D0142093A295888CE4A507B4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0497EE70D0142093A295888CE4A507B4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_304DB547E50BBDA839E7888CE4A592BB" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0497EE70D0142093A295888CE4A507B4" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_AllegroDiagnosticsCorpMember" xlink:label="loc_vcyt_AllegroDiagnosticsCorpMember_7ABECE60BBDE86B19FEA888CE4A56EB7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0497EE70D0142093A295888CE4A507B4" xlink:to="loc_vcyt_AllegroDiagnosticsCorpMember_7ABECE60BBDE86B19FEA888CE4A56EB7" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ScheduleOfComponentsOfAcquisitionConsiderationTableTextBlock" xlink:label="loc_vcyt_ScheduleOfComponentsOfAcquisitionConsiderationTableTextBlock_68F291AB2E7471694484888CE4A59F1C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2FE3EC371DCF7A4D79AD888CE4A56C4B" xlink:to="loc_vcyt_ScheduleOfComponentsOfAcquisitionConsiderationTableTextBlock_68F291AB2E7471694484888CE4A59F1C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock_506F394EDFA4C89F65D1888CE4A55573" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2FE3EC371DCF7A4D79AD888CE4A56C4B" xlink:to="loc_us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock_506F394EDFA4C89F65D1888CE4A55573" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BusinessAcquisitionProFormaInformationTextBlock" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaInformationTextBlock_19BB886DA479A59CEFEA888CE4A59677" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2FE3EC371DCF7A4D79AD888CE4A56C4B" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaInformationTextBlock_19BB886DA479A59CEFEA888CE4A59677" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/CommitmentsAndContingenciesCapitalLeaseDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CapitalLeasedAssetsLineItems" xlink:label="loc_us-gaap_CapitalLeasedAssetsLineItems_A1E0E64CA4DFE620DB57CDC71630D114" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfCapitalLeasedAsssetsTable" xlink:label="loc_us-gaap_ScheduleOfCapitalLeasedAsssetsTable_44535AE6601EC011C370CDC7162FA827" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_A1E0E64CA4DFE620DB57CDC71630D114" xlink:to="loc_us-gaap_ScheduleOfCapitalLeasedAsssetsTable_44535AE6601EC011C370CDC7162FA827" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_19AA3BD1001427008B81CDCB0BE9D165" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCapitalLeasedAsssetsTable_44535AE6601EC011C370CDC7162FA827" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_19AA3BD1001427008B81CDCB0BE9D165" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_E32E0417539BBE12193DCDCB0C002C6C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_19AA3BD1001427008B81CDCB0BE9D165" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_E32E0417539BBE12193DCDCB0C002C6C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_E32E0417539BBE12193DCDCB0C002C6C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_19AA3BD1001427008B81CDCB0BE9D165" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_E32E0417539BBE12193DCDCB0C002C6C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccruedLiabilitiesMember" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_EB8BB37E9629C0798885CDE7230F8581" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_E32E0417539BBE12193DCDCB0C002C6C" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_EB8BB37E9629C0798885CDE7230F8581" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CapitalLeaseObligationsMember" xlink:label="loc_us-gaap_CapitalLeaseObligationsMember_83E6E2B5F6BB09CE6CB4CDE759E7C051" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_E32E0417539BBE12193DCDCB0C002C6C" xlink:to="loc_us-gaap_CapitalLeaseObligationsMember_83E6E2B5F6BB09CE6CB4CDE759E7C051" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_A12F289DB21FD7F5405ECDC80A02B47E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCapitalLeasedAsssetsTable_44535AE6601EC011C370CDC7162FA827" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_A12F289DB21FD7F5405ECDC80A02B47E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A623957C968B4A4352F2CDC80A08CDB8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_A12F289DB21FD7F5405ECDC80A02B47E" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A623957C968B4A4352F2CDC80A08CDB8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A623957C968B4A4352F2CDC80A08CDB8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_A12F289DB21FD7F5405ECDC80A02B47E" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A623957C968B4A4352F2CDC80A08CDB8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquipmentMember" xlink:label="loc_us-gaap_EquipmentMember_C53EEED37B5245E6D5D9CDC842FA361F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A623957C968B4A4352F2CDC80A08CDB8" xlink:to="loc_us-gaap_EquipmentMember_C53EEED37B5245E6D5D9CDC842FA361F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CapitalLeasedAssetsGross" xlink:label="loc_us-gaap_CapitalLeasedAssetsGross_AF87AB79E032AC37D9F3CDC7D985CF5B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_A1E0E64CA4DFE620DB57CDC71630D114" xlink:to="loc_us-gaap_CapitalLeasedAssetsGross_AF87AB79E032AC37D9F3CDC7D985CF5B" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CapitalLeaseUpfrontPayment" xlink:label="loc_vcyt_CapitalLeaseUpfrontPayment_8567604015A943BFD3FDCDF4AB068C28" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_A1E0E64CA4DFE620DB57CDC71630D114" xlink:to="loc_vcyt_CapitalLeaseUpfrontPayment_8567604015A943BFD3FDCDF4AB068C28" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPayments" xlink:label="loc_us-gaap_CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPayments_C0381F238F13A852879CCDC969F99914" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_A1E0E64CA4DFE620DB57CDC71630D114" xlink:to="loc_us-gaap_CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPayments_C0381F238F13A852879CCDC969F99914" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CapitalLeasesFutureMinimumPaymentsDue" xlink:label="loc_us-gaap_CapitalLeasesFutureMinimumPaymentsDue_034DC0EF5D0BC419680ACDCA48E0C47B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_A1E0E64CA4DFE620DB57CDC71630D114" xlink:to="loc_us-gaap_CapitalLeasesFutureMinimumPaymentsDue_034DC0EF5D0BC419680ACDCA48E0C47B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CapitalLeasesFutureMinimumPaymentsDueCurrent" xlink:label="loc_us-gaap_CapitalLeasesFutureMinimumPaymentsDueCurrent_4AF43B9BD91689C12BCECDF138971DA3" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_A1E0E64CA4DFE620DB57CDC71630D114" xlink:to="loc_us-gaap_CapitalLeasesFutureMinimumPaymentsDueCurrent_4AF43B9BD91689C12BCECDF138971DA3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CapitalLeasesFutureMinimumPaymentsDueInTwoYears" xlink:label="loc_us-gaap_CapitalLeasesFutureMinimumPaymentsDueInTwoYears_ACB886F5CEC47A80432ECDF01E0B64D9" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_A1E0E64CA4DFE620DB57CDC71630D114" xlink:to="loc_us-gaap_CapitalLeasesFutureMinimumPaymentsDueInTwoYears_ACB886F5CEC47A80432ECDF01E0B64D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CapitalLeasesFutureMinimumPaymentsDueInThreeYears" xlink:label="loc_us-gaap_CapitalLeasesFutureMinimumPaymentsDueInThreeYears_D06A711C9DB0B1B3FBDACDF076F9EFB1" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_A1E0E64CA4DFE620DB57CDC71630D114" xlink:to="loc_us-gaap_CapitalLeasesFutureMinimumPaymentsDueInThreeYears_D06A711C9DB0B1B3FBDACDF076F9EFB1" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/CommitmentsAndContingenciesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasedAssetsLineItems" xlink:label="loc_us-gaap_OperatingLeasedAssetsLineItems_5CCF726FE62866D52EC658949EBD8D52" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfOperatingLeasedAssetsTable" xlink:label="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_E79F3AE7211060308A0258949EBC96D1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_5CCF726FE62866D52EC658949EBD8D52" xlink:to="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_E79F3AE7211060308A0258949EBC96D1" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_89165547F24F240E0F915899490ECB7A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_E79F3AE7211060308A0258949EBC96D1" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_89165547F24F240E0F915899490ECB7A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_5416BE04C2460D6BC9F65899491DC3BC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_89165547F24F240E0F915899490ECB7A" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_5416BE04C2460D6BC9F65899491DC3BC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_5416BE04C2460D6BC9F65899491DC3BC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_89165547F24F240E0F915899490ECB7A" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_5416BE04C2460D6BC9F65899491DC3BC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_B26835FF3187A8CE05F65899A6A9654A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_5416BE04C2460D6BC9F65899491DC3BC" xlink:to="loc_us-gaap_SubsequentEventMember_B26835FF3187A8CE05F65899A6A9654A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_6C7EA1A5C0EF3EAEA7BB58949EBD7952" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_E79F3AE7211060308A0258949EBC96D1" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_6C7EA1A5C0EF3EAEA7BB58949EBD7952" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_730EE0B22532E6DA45BF58949EBDF7EB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_6C7EA1A5C0EF3EAEA7BB58949EBD7952" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_730EE0B22532E6DA45BF58949EBDF7EB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_730EE0B22532E6DA45BF58949EBDF7EB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_6C7EA1A5C0EF3EAEA7BB58949EBD7952" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_730EE0B22532E6DA45BF58949EBDF7EB" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_HeadquartersAndLaboratoryFacilitiesSouthSanFranciscoLeaseTwoMember" xlink:label="loc_vcyt_HeadquartersAndLaboratoryFacilitiesSouthSanFranciscoLeaseTwoMember_C8EEEA4DA40DEFBFA77D58949EBD0AE0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_730EE0B22532E6DA45BF58949EBDF7EB" xlink:to="loc_vcyt_HeadquartersAndLaboratoryFacilitiesSouthSanFranciscoLeaseTwoMember_C8EEEA4DA40DEFBFA77D58949EBD0AE0" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_LaboratoryFacilitiesAustinTexasMember" xlink:label="loc_vcyt_LaboratoryFacilitiesAustinTexasMember_162FD37C5F5B60BB1D7D58949EBD7532" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_730EE0B22532E6DA45BF58949EBDF7EB" xlink:to="loc_vcyt_LaboratoryFacilitiesAustinTexasMember_162FD37C5F5B60BB1D7D58949EBD7532" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_LesseeLeasingArrangementsOperatingLeasesSpaceLeased" xlink:label="loc_vcyt_LesseeLeasingArrangementsOperatingLeasesSpaceLeased_290A196749696A9F7CF558949EBD7525" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_5CCF726FE62866D52EC658949EBD8D52" xlink:to="loc_vcyt_LesseeLeasingArrangementsOperatingLeasesSpaceLeased_290A196749696A9F7CF558949EBD7525" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_LeaseModificationConsiderationReceived" xlink:label="loc_vcyt_LeaseModificationConsiderationReceived_27D62DC84A1CFADE9D7058989727392F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_5CCF726FE62866D52EC658949EBD8D52" xlink:to="loc_vcyt_LeaseModificationConsiderationReceived_27D62DC84A1CFADE9D7058989727392F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SecurityDeposit" xlink:label="loc_us-gaap_SecurityDeposit_504BD984635FBC23C25F58949EBDA27C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_5CCF726FE62866D52EC658949EBD8D52" xlink:to="loc_us-gaap_SecurityDeposit_504BD984635FBC23C25F58949EBDA27C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_038102DB0C083241093058949EBD6246" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_5CCF726FE62866D52EC658949EBD8D52" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_038102DB0C083241093058949EBD6246" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_BDED8B547EDC781AB3EC58949EBD65BD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_038102DB0C083241093058949EBD6246" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_BDED8B547EDC781AB3EC58949EBD65BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_59C1F8323B7B09F8A59058949EBDB322" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_038102DB0C083241093058949EBD6246" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_59C1F8323B7B09F8A59058949EBDB322" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_29FE050034D3B37F4CD058949EBDAAE4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_038102DB0C083241093058949EBD6246" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_29FE050034D3B37F4CD058949EBDAAE4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_EDA7BCF2DB406122315658949EBDA112" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_038102DB0C083241093058949EBD6246" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_EDA7BCF2DB406122315658949EBDA112" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears_3A9868CCDC715AEF924058949EBD0C7E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_038102DB0C083241093058949EBD6246" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears_3A9868CCDC715AEF924058949EBD0C7E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter_441B1B9C0E5E68ACDFF658949EBD406A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_038102DB0C083241093058949EBD6246" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter_441B1B9C0E5E68ACDFF658949EBD406A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_91A09CA6A61E6BE6F7E958949EBDE3F6" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_038102DB0C083241093058949EBD6246" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_91A09CA6A61E6BE6F7E958949EBDE3F6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesRentExpenseNet" xlink:label="loc_us-gaap_OperatingLeasesRentExpenseNet_83C9DD078738CC05C75758949EBD5955" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_038102DB0C083241093058949EBD6246" xlink:to="loc_us-gaap_OperatingLeasesRentExpenseNet_83C9DD078738CC05C75758949EBD5955" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_PurchaseObligationAbstract" xlink:label="loc_vcyt_PurchaseObligationAbstract_47216EA6AF9FE2E2164558949EBE6DBD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_5CCF726FE62866D52EC658949EBD8D52" xlink:to="loc_vcyt_PurchaseObligationAbstract_47216EA6AF9FE2E2164558949EBE6DBD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PurchaseObligation" xlink:label="loc_us-gaap_PurchaseObligation_869CDC002499D03BE66058949EBE5B9B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_PurchaseObligationAbstract_47216EA6AF9FE2E2164558949EBE6DBD" xlink:to="loc_us-gaap_PurchaseObligation_869CDC002499D03BE66058949EBE5B9B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/CommitmentsAndContingenciesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/Debt" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/DebtCreditAgreementDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_587870435222762807456C1DB81DCCD3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_us-gaap_DebtInstrumentTable_587870435222762807456C1DB81DCCD3" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_B8DDF01225550041B62A6C1DB81D5D33" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_587870435222762807456C1DB81DCCD3" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_B8DDF01225550041B62A6C1DB81D5D33" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_F1A3807D9044478627026C1DB81D8A6B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_B8DDF01225550041B62A6C1DB81D5D33" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_F1A3807D9044478627026C1DB81D8A6B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_F1A3807D9044478627026C1DB81D8A6B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_B8DDF01225550041B62A6C1DB81D5D33" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_F1A3807D9044478627026C1DB81D8A6B" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_VisiumMember" xlink:label="loc_vcyt_VisiumMember_A725E4A012746E416F276C1DB81D795F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_F1A3807D9044478627026C1DB81D8A6B" xlink:to="loc_vcyt_VisiumMember_A725E4A012746E416F276C1DB81D795F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_2A3B7CA13B0CEC77DA0A6C1DB81DBB4D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_587870435222762807456C1DB81DCCD3" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_2A3B7CA13B0CEC77DA0A6C1DB81DBB4D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_D99EB2BCE83A0E1725FD6C1DB81DD122_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2A3B7CA13B0CEC77DA0A6C1DB81DBB4D" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_D99EB2BCE83A0E1725FD6C1DB81DD122_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_D99EB2BCE83A0E1725FD6C1DB81DD122" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2A3B7CA13B0CEC77DA0A6C1DB81DBB4D" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_D99EB2BCE83A0E1725FD6C1DB81DD122" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_211800CDC1C7C82688306C1DB81D5AD7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_D99EB2BCE83A0E1725FD6C1DB81DD122" xlink:to="loc_us-gaap_LineOfCreditMember_211800CDC1C7C82688306C1DB81D5AD7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_A7E2843D4F634EF181696C1DB81DADDC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_587870435222762807456C1DB81DCCD3" xlink:to="loc_us-gaap_DebtInstrumentAxis_A7E2843D4F634EF181696C1DB81DADDC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_CCBF02C3A59D5906C7EE6C1DB81D3897_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_A7E2843D4F634EF181696C1DB81DADDC" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_CCBF02C3A59D5906C7EE6C1DB81D3897_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_CCBF02C3A59D5906C7EE6C1DB81D3897" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_A7E2843D4F634EF181696C1DB81DADDC" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_CCBF02C3A59D5906C7EE6C1DB81D3897" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_InitialTermLoanMember" xlink:label="loc_vcyt_InitialTermLoanMember_6E120E676B4169FF46736C1DB81D61C9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_CCBF02C3A59D5906C7EE6C1DB81D3897" xlink:to="loc_vcyt_InitialTermLoanMember_6E120E676B4169FF46736C1DB81D61C9" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_SecondTermLoanMember" xlink:label="loc_vcyt_SecondTermLoanMember_1A26B681F4DDB392099C6C1DB81D74E4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_CCBF02C3A59D5906C7EE6C1DB81D3897" xlink:to="loc_vcyt_SecondTermLoanMember_1A26B681F4DDB392099C6C1DB81D74E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_234736D102FCC8D645BE6C1DB81E1624" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_587870435222762807456C1DB81DCCD3" xlink:to="loc_us-gaap_RangeAxis_234736D102FCC8D645BE6C1DB81E1624" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_24F6987E643F73FD00EB6C1DB81E3E5E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_234736D102FCC8D645BE6C1DB81E1624" xlink:to="loc_us-gaap_RangeMember_24F6987E643F73FD00EB6C1DB81E3E5E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_24F6987E643F73FD00EB6C1DB81E3E5E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_234736D102FCC8D645BE6C1DB81E1624" xlink:to="loc_us-gaap_RangeMember_24F6987E643F73FD00EB6C1DB81E3E5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_B903F292AAE6CAB480646C1DB823EC24" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_24F6987E643F73FD00EB6C1DB81E3E5E" xlink:to="loc_us-gaap_MaximumMember_B903F292AAE6CAB480646C1DB823EC24" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockIssuedDuringPeriodSharesWarrantsExercised" xlink:label="loc_vcyt_StockIssuedDuringPeriodSharesWarrantsExercised_6F2FD7E47C36BA76023F6C1DB823F3A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_StockIssuedDuringPeriodSharesWarrantsExercised_6F2FD7E47C36BA76023F6C1DB823F3A1" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_NumberOfTermLoans" xlink:label="loc_vcyt_NumberOfTermLoans_DC2AC9A1428854F4A5EA6C1DB823EF89" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_NumberOfTermLoans_DC2AC9A1428854F4A5EA6C1DB823EF89" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_2902D7111BA959B665186C1DB823FEBC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_2902D7111BA959B665186C1DB823FEBC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_4A6636575CA4E75C5E746C1DB82326E8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_4A6636575CA4E75C5E746C1DB82326E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_D71DB35779FB4212F3746C1DB8239544" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_D71DB35779FB4212F3746C1DB8239544" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_BB0D4B972B46548446836C1DB824C9EC" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_BB0D4B972B46548446836C1DB824C9EC" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentNumberOfInstallments" xlink:label="loc_vcyt_DebtInstrumentNumberOfInstallments_C97323D84D29D6BB99CA6C1DB8246CA6" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentNumberOfInstallments_C97323D84D29D6BB99CA6C1DB8246CA6" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TermOfDebtWithEqualQuarterlyInstallments" xlink:label="loc_vcyt_TermOfDebtWithEqualQuarterlyInstallments_A82A353814434A208DA96C1DB82423E6" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_TermOfDebtWithEqualQuarterlyInstallments_A82A353814434A208DA96C1DB82423E6" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentFixedRatePercentagePaidInCash" xlink:label="loc_vcyt_DebtInstrumentFixedRatePercentagePaidInCash_C9390DE8FB8AE5C895206C1DB82477CB" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentFixedRatePercentagePaidInCash_C9390DE8FB8AE5C895206C1DB82477CB" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentInterestPaidInKindPercentage" xlink:label="loc_vcyt_DebtInstrumentInterestPaidInKindPercentage_0DF71856F0EB2E0A345E6C1DB8245614" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentInterestPaidInKindPercentage_0DF71856F0EB2E0A345E6C1DB8245614" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PaidInKindInterest" xlink:label="loc_us-gaap_PaidInKindInterest_03F01E1A2F69A26CB0C46C1DB824D18B" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_us-gaap_PaidInKindInterest_03F01E1A2F69A26CB0C46C1DB824D18B" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentMinimumPrepaymentAllowed" xlink:label="loc_vcyt_DebtInstrumentMinimumPrepaymentAllowed_838DA7AE91019415B5336C1DB824C4ED" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentMinimumPrepaymentAllowed_838DA7AE91019415B5336C1DB824C4ED" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPrepaymentAmountExcessMultiple" xlink:label="loc_vcyt_DebtInstrumentPrepaymentAmountExcessMultiple_49C048895C2C9B98F4FA6C1DB82488EA" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentPrepaymentAmountExcessMultiple_49C048895C2C9B98F4FA6C1DB82488EA" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodOne" xlink:label="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodOne_F61F169278BFB25B72CF6C1DB82487CD" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodOne_F61F169278BFB25B72CF6C1DB82487CD" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodTwo" xlink:label="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodTwo_4491F611E65A7355926E6C1DB82425FA" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodTwo_4491F611E65A7355926E6C1DB82425FA" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodThree" xlink:label="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodThree_C077124B277BD5DD510A6C1DB8249CAA" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodThree_C077124B277BD5DD510A6C1DB8249CAA" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodFour" xlink:label="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodFour_08AA9EADC582CB1FEDF06C1DB8244A3B" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentPeriodFour_08AA9EADC582CB1FEDF06C1DB8244A3B" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPeriodForWhichRightsEquityFinancings" xlink:label="loc_vcyt_DebtInstrumentPeriodForWhichRightsEquityFinancings_CBECF8AA1E1CA5D4A4F76C1DB824DCA5" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentPeriodForWhichRightsEquityFinancings_CBECF8AA1E1CA5D4A4F76C1DB824DCA5" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentFutureEquityFinancingsAmount" xlink:label="loc_vcyt_DebtInstrumentFutureEquityFinancingsAmount_0F1DE2F172ADB14BEAAB6C1DB824959F" xlink:type="locator" />
    <link:definitionArc order="19" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_DDE415CFFC0E93AFBF4A6C1DB823789D" xlink:to="loc_vcyt_DebtInstrumentFutureEquityFinancingsAmount_0F1DE2F172ADB14BEAAB6C1DB824959F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/DebtCreditAgreementTabularDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_38379AB9FAAC7D9CA3436C7AFA47EC8A" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_4FFD75EAA2C269E8D6036C7AFA47B63F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38379AB9FAAC7D9CA3436C7AFA47EC8A" xlink:to="loc_us-gaap_DebtInstrumentTable_4FFD75EAA2C269E8D6036C7AFA47B63F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_CBE61CDD61B8F759E79C6C7AFA473EC9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4FFD75EAA2C269E8D6036C7AFA47B63F" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_CBE61CDD61B8F759E79C6C7AFA473EC9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_569660C01C38FB0C75C56C7AFA47498F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_CBE61CDD61B8F759E79C6C7AFA473EC9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_569660C01C38FB0C75C56C7AFA47498F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_569660C01C38FB0C75C56C7AFA47498F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_CBE61CDD61B8F759E79C6C7AFA473EC9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_569660C01C38FB0C75C56C7AFA47498F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_DC20AFF7FE510BC00C216C7AFA4777F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_569660C01C38FB0C75C56C7AFA47498F" xlink:to="loc_us-gaap_LineOfCreditMember_DC20AFF7FE510BC00C216C7AFA4777F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_4A01C9FDD450469021D46C7AFA47DE6F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4FFD75EAA2C269E8D6036C7AFA47B63F" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_4A01C9FDD450469021D46C7AFA47DE6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_4B879208934992B2644F6C7AFA47CE6A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_4A01C9FDD450469021D46C7AFA47DE6F" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_4B879208934992B2644F6C7AFA47CE6A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_4B879208934992B2644F6C7AFA47CE6A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_4A01C9FDD450469021D46C7AFA47DE6F" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_4B879208934992B2644F6C7AFA47CE6A" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_VisiumMember" xlink:label="loc_vcyt_VisiumMember_DA191B1CB9B784209C5B6C7AFA47BEC8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_4B879208934992B2644F6C7AFA47CE6A" xlink:to="loc_vcyt_VisiumMember_DA191B1CB9B784209C5B6C7AFA47BEC8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_F790F62F6A124A3C357B6C7AFA4791CE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38379AB9FAAC7D9CA3436C7AFA47EC8A" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_F790F62F6A124A3C357B6C7AFA4791CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscount" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_AD1B21B10F6DABE56F296C7AFA4702F2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38379AB9FAAC7D9CA3436C7AFA47EC8A" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_AD1B21B10F6DABE56F296C7AFA4702F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongTermDebt" xlink:label="loc_us-gaap_LongTermDebt_76475AC99573C9B576816C96122B8D5C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38379AB9FAAC7D9CA3436C7AFA47EC8A" xlink:to="loc_us-gaap_LongTermDebt_76475AC99573C9B576816C96122B8D5C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_B035662FBF97189BD4716C7AFA47E962" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38379AB9FAAC7D9CA3436C7AFA47EC8A" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_B035662FBF97189BD4716C7AFA47E962" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_8A992A4439B6BCDD79B96C7AFA476962" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38379AB9FAAC7D9CA3436C7AFA47EC8A" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_8A992A4439B6BCDD79B96C7AFA476962" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_3A3B380AC0029ED0C4296C7AFA48A38B" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38379AB9FAAC7D9CA3436C7AFA47EC8A" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_3A3B380AC0029ED0C4296C7AFA48A38B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/DebtLoanAndSecurityAgreementDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_D9147704BF224940547F6C7AFA42915F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_us-gaap_DebtInstrumentTable_D9147704BF224940547F6C7AFA42915F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_96C21D4C880C7B0F70396C7AFA424327" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_D9147704BF224940547F6C7AFA42915F" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_96C21D4C880C7B0F70396C7AFA424327" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_A162804D8606440AF4536C7AFA422C0C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_96C21D4C880C7B0F70396C7AFA424327" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_A162804D8606440AF4536C7AFA422C0C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_A162804D8606440AF4536C7AFA422C0C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_96C21D4C880C7B0F70396C7AFA424327" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_A162804D8606440AF4536C7AFA422C0C" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ConvertiblePreferredStockWarrantsMember" xlink:label="loc_vcyt_ConvertiblePreferredStockWarrantsMember_52EF5FF4986F4789C5316C7AFA426738" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_A162804D8606440AF4536C7AFA422C0C" xlink:to="loc_vcyt_ConvertiblePreferredStockWarrantsMember_52EF5FF4986F4789C5316C7AFA426738" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_16FFD214B1F5E41902996C7AFA42FA39" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_D9147704BF224940547F6C7AFA42915F" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_16FFD214B1F5E41902996C7AFA42FA39" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_E22BCF91EB3E79642EB96C7AFA428447_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_16FFD214B1F5E41902996C7AFA42FA39" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_E22BCF91EB3E79642EB96C7AFA428447_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_E22BCF91EB3E79642EB96C7AFA428447" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_16FFD214B1F5E41902996C7AFA42FA39" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_E22BCF91EB3E79642EB96C7AFA428447" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TermLoanMember" xlink:label="loc_vcyt_TermLoanMember_433C81FBA57F73FFEAFF6C7AFA428D26" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_E22BCF91EB3E79642EB96C7AFA428447" xlink:to="loc_vcyt_TermLoanMember_433C81FBA57F73FFEAFF6C7AFA428D26" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_A58B9C4DD468F1E3AEBC6C7AFA427658" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_D9147704BF224940547F6C7AFA42915F" xlink:to="loc_us-gaap_DebtInstrumentAxis_A58B9C4DD468F1E3AEBC6C7AFA427658" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_786344C6F07CE1B351196C7AFA42987D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_A58B9C4DD468F1E3AEBC6C7AFA427658" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_786344C6F07CE1B351196C7AFA42987D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_786344C6F07CE1B351196C7AFA42987D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_A58B9C4DD468F1E3AEBC6C7AFA427658" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_786344C6F07CE1B351196C7AFA42987D" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TermLoanDue2017Member" xlink:label="loc_vcyt_TermLoanDue2017Member_1CD8B36DD6184B6BBFDC6C7AFA43ED9F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_786344C6F07CE1B351196C7AFA42987D" xlink:to="loc_vcyt_TermLoanDue2017Member_1CD8B36DD6184B6BBFDC6C7AFA43ED9F" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TermLoanTrancheOneMember" xlink:label="loc_vcyt_TermLoanTrancheOneMember_8A4135B25B5DC064AD576C7AFA438C1A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_786344C6F07CE1B351196C7AFA42987D" xlink:to="loc_vcyt_TermLoanTrancheOneMember_8A4135B25B5DC064AD576C7AFA438C1A" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TermLoanTrancheTwoMember" xlink:label="loc_vcyt_TermLoanTrancheTwoMember_7CEAB9A27C587D7D50516C7AFA4393E4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_786344C6F07CE1B351196C7AFA42987D" xlink:to="loc_vcyt_TermLoanTrancheTwoMember_7CEAB9A27C587D7D50516C7AFA4393E4" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TermLoanTrancheThreeMember" xlink:label="loc_vcyt_TermLoanTrancheThreeMember_0D170AB003ECBE2793026C7AFA431B93" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_786344C6F07CE1B351196C7AFA42987D" xlink:to="loc_vcyt_TermLoanTrancheThreeMember_0D170AB003ECBE2793026C7AFA431B93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_53FD49DA733A4E7ED3076C7AFA430E76" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_53FD49DA733A4E7ED3076C7AFA430E76" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_NumberOfTranches" xlink:label="loc_vcyt_NumberOfTranches_14D9E209CE340788BD4E6C7AFA430BA6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_NumberOfTranches_14D9E209CE340788BD4E6C7AFA430BA6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" xlink:label="loc_us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_CAC48B5D05C4EA97177A6C7AFA4379F8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_CAC48B5D05C4EA97177A6C7AFA4379F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount" xlink:label="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_EEE8E4926A844F3D115D6C7AFA432640" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_EEE8E4926A844F3D115D6C7AFA432640" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentNumberOfInstallments" xlink:label="loc_vcyt_DebtInstrumentNumberOfInstallments_0CDC3F7707379C88AE886C7AFA43C581" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_DebtInstrumentNumberOfInstallments_0CDC3F7707379C88AE886C7AFA43C581" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPeriodAfterWhichDebtIsRepayable" xlink:label="loc_vcyt_DebtInstrumentPeriodAfterWhichDebtIsRepayable_ABA67CB8339C372B1A5F6C7AFA431A6D" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_DebtInstrumentPeriodAfterWhichDebtIsRepayable_ABA67CB8339C372B1A5F6C7AFA431A6D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_8AB61330039263C3AEF66C7AFA43A2A2" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_8AB61330039263C3AEF66C7AFA43A2A2" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentWithinOneYearOfOrigination" xlink:label="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentWithinOneYearOfOrigination_58C3413D4CC96FA603E26C7AFA43F205" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentWithinOneYearOfOrigination_58C3413D4CC96FA603E26C7AFA43F205" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentWithinTwoYearsOfOrigination" xlink:label="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentWithinTwoYearsOfOrigination_42EE3AD7AF62596D9B746C7AFA438DF9" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentWithinTwoYearsOfOrigination_42EE3AD7AF62596D9B746C7AFA438DF9" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentAfterTwoYearsOfOrigination" xlink:label="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentAfterTwoYearsOfOrigination_4E712F46530E11E0A3EC6C7AFA4342B8" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_DebtInstrumentPenaltyPercentageOnPrepaymentAfterTwoYearsOfOrigination_4E712F46530E11E0A3EC6C7AFA4342B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProceedsFromRepaymentsOfDebt" xlink:label="loc_us-gaap_ProceedsFromRepaymentsOfDebt_4DE29330B82CCB704AF66C7AFA43EDD4" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_us-gaap_ProceedsFromRepaymentsOfDebt_4DE29330B82CCB704AF66C7AFA43EDD4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InterestPaid" xlink:label="loc_us-gaap_InterestPaid_34C111B9804194D078A96C7AFA43FE01" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_us-gaap_InterestPaid_34C111B9804194D078A96C7AFA43FE01" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentEndOfTermPaymentAmount" xlink:label="loc_vcyt_DebtInstrumentEndOfTermPaymentAmount_B3986674D966850105F26C7AFA4350EC" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_DebtInstrumentEndOfTermPaymentAmount_B3986674D966850105F26C7AFA4350EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PaymentsOfDebtExtinguishmentCosts" xlink:label="loc_us-gaap_PaymentsOfDebtExtinguishmentCosts_7810A042E1CD12B7267D6C7AFA438236" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_us-gaap_PaymentsOfDebtExtinguishmentCosts_7810A042E1CD12B7267D6C7AFA438236" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentPrepaymentPremium" xlink:label="loc_vcyt_DebtInstrumentPrepaymentPremium_09291FF677DE6ED836306C7AFA435D36" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_DebtInstrumentPrepaymentPremium_09291FF677DE6ED836306C7AFA435D36" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentThirdPartyFeeAmountPaid" xlink:label="loc_vcyt_DebtInstrumentThirdPartyFeeAmountPaid_60E557AB1E08AEDAE33A6C7AFA4439E9" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_DebtInstrumentThirdPartyFeeAmountPaid_60E557AB1E08AEDAE33A6C7AFA4439E9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_B506C8D5D42C7862755A6C7AFA44EADD" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_B506C8D5D42C7862755A6C7AFA44EADD" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ClassOfWarrantOrRightNumberOfSecuritiesForWhichWarrantsWillBecomeExercisableInEventOfConversionOfPreferredStockIntoCommonStock" xlink:label="loc_vcyt_ClassOfWarrantOrRightNumberOfSecuritiesForWhichWarrantsWillBecomeExercisableInEventOfConversionOfPreferredStockIntoCommonStock_FA95B2096AC5B7C2F3916C7AFA444CD8" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_ClassOfWarrantOrRightNumberOfSecuritiesForWhichWarrantsWillBecomeExercisableInEventOfConversionOfPreferredStockIntoCommonStock_FA95B2096AC5B7C2F3916C7AFA444CD8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DerivativeLiabilitiesCurrent" xlink:label="loc_us-gaap_DerivativeLiabilitiesCurrent_21EE8DE397AC6DFD7F9E6C7AFA447BF8" xlink:type="locator" />
    <link:definitionArc order="19" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_21EE8DE397AC6DFD7F9E6C7AFA447BF8" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentRemainingDiscountAmortizationPeriod" xlink:label="loc_vcyt_DebtInstrumentRemainingDiscountAmortizationPeriod_FDDED2206F05122AAEA56C7AFA44CB73" xlink:type="locator" />
    <link:definitionArc order="20" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_DebtInstrumentRemainingDiscountAmortizationPeriod_FDDED2206F05122AAEA56C7AFA44CB73" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockIssuedDuringPeriodSharesWarrantsExercised" xlink:label="loc_vcyt_StockIssuedDuringPeriodSharesWarrantsExercised_4B3CF57D115CD64168C76C96FD592DD9" xlink:type="locator" />
    <link:definitionArc order="21" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3DCF45689CE1577C4DAE6C7AFA439146" xlink:to="loc_vcyt_StockIssuedDuringPeriodSharesWarrantsExercised_4B3CF57D115CD64168C76C96FD592DD9" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/DebtLoanAndSecurityAgreementTabularDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_C8D0A1070110ABFF6A0C6C7AFA3C1A96" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_3EABB6BA83AEABF1086A6C7AFA3C20B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C8D0A1070110ABFF6A0C6C7AFA3C1A96" xlink:to="loc_us-gaap_DebtInstrumentTable_3EABB6BA83AEABF1086A6C7AFA3C20B2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_3D67BFFBAC964EFC901C6C96B344AD6C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3EABB6BA83AEABF1086A6C7AFA3C20B2" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_3D67BFFBAC964EFC901C6C96B344AD6C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_18417DCCBA45768134FE6C96B349FAAA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_3D67BFFBAC964EFC901C6C96B344AD6C" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_18417DCCBA45768134FE6C96B349FAAA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_18417DCCBA45768134FE6C96B349FAAA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_3D67BFFBAC964EFC901C6C96B344AD6C" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_18417DCCBA45768134FE6C96B349FAAA" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ConvertiblePreferredStockWarrantsMember" xlink:label="loc_vcyt_ConvertiblePreferredStockWarrantsMember_93278B99AA40DA53D2AC6C96B3C4AD20" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_18417DCCBA45768134FE6C96B349FAAA" xlink:to="loc_vcyt_ConvertiblePreferredStockWarrantsMember_93278B99AA40DA53D2AC6C96B3C4AD20" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_00F9FB5F74AA8FE421756C7AFA3CF4BF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3EABB6BA83AEABF1086A6C7AFA3C20B2" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_00F9FB5F74AA8FE421756C7AFA3CF4BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_517925B23696C2C7F4886C7AFA3C6963_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_00F9FB5F74AA8FE421756C7AFA3CF4BF" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_517925B23696C2C7F4886C7AFA3C6963_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_517925B23696C2C7F4886C7AFA3C6963" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_00F9FB5F74AA8FE421756C7AFA3CF4BF" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_517925B23696C2C7F4886C7AFA3C6963" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TermLoanMember" xlink:label="loc_vcyt_TermLoanMember_FA0B2AAA3FEC02EEB0006C7AFA3CB332" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_517925B23696C2C7F4886C7AFA3C6963" xlink:to="loc_vcyt_TermLoanMember_FA0B2AAA3FEC02EEB0006C7AFA3CB332" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_LongTermDebtAndAccruedEndOfTermPayment" xlink:label="loc_vcyt_LongTermDebtAndAccruedEndOfTermPayment_C2C6D1DF2ECC10D6D3E26C7AFA3CF015" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C8D0A1070110ABFF6A0C6C7AFA3C1A96" xlink:to="loc_vcyt_LongTermDebtAndAccruedEndOfTermPayment_C2C6D1DF2ECC10D6D3E26C7AFA3CF015" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscount" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_2DB8A52F58DC76365B616C7AFA3C04E2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C8D0A1070110ABFF6A0C6C7AFA3C1A96" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_2DB8A52F58DC76365B616C7AFA3C04E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongTermDebt" xlink:label="loc_us-gaap_LongTermDebt_8F62C722B082E26E96B96C7AFA3CFE77" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C8D0A1070110ABFF6A0C6C7AFA3C1A96" xlink:to="loc_us-gaap_LongTermDebt_8F62C722B082E26E96B96C7AFA3CFE77" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/DebtTables" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_70A77E08A16D71BA4F627533C79D3DD4" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_37ABE900A73A79C7C9BD7533C79D6399" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_70A77E08A16D71BA4F627533C79D3DD4" xlink:to="loc_us-gaap_DebtInstrumentTable_37ABE900A73A79C7C9BD7533C79D6399" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_6693D86613756FC661607533C79D06A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_37ABE900A73A79C7C9BD7533C79D6399" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_6693D86613756FC661607533C79D06A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_73403810DE610CAD0D607533C79D2E6B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_6693D86613756FC661607533C79D06A0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_73403810DE610CAD0D607533C79D2E6B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_73403810DE610CAD0D607533C79D2E6B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_6693D86613756FC661607533C79D06A0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_73403810DE610CAD0D607533C79D2E6B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_EA6704DBFDAF45FAC0E67533C79DB931" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_73403810DE610CAD0D607533C79D2E6B" xlink:to="loc_us-gaap_LineOfCreditMember_EA6704DBFDAF45FAC0E67533C79DB931" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TermLoanMember" xlink:label="loc_vcyt_TermLoanMember_FBF792982D1FCAEFA18D7533C79D89DA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_73403810DE610CAD0D607533C79D2E6B" xlink:to="loc_vcyt_TermLoanMember_FBF792982D1FCAEFA18D7533C79D89DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ContractualObligationFiscalYearMaturityScheduleTableTextBlock" xlink:label="loc_us-gaap_ContractualObligationFiscalYearMaturityScheduleTableTextBlock_78E47CEB33F5B2593A1C7533C79DEB00" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_70A77E08A16D71BA4F627533C79D3DD4" xlink:to="loc_us-gaap_ContractualObligationFiscalYearMaturityScheduleTableTextBlock_78E47CEB33F5B2593A1C7533C79DEB00" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfDebtTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfDebtTableTextBlock_02DC8B137D744B908C497533C79D206A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_70A77E08A16D71BA4F627533C79D3DD4" xlink:to="loc_us-gaap_ScheduleOfDebtTableTextBlock_02DC8B137D744B908C497533C79D206A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/DocumentAndEntityInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/FairValueMeasurements" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/FairValueMeasurementsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_DFD1218431A9AB36DD7B755A8CF30C79" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A68D8311176AD48DF0A3755A8CF12EF9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_DFD1218431A9AB36DD7B755A8CF30C79" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A68D8311176AD48DF0A3755A8CF12EF9" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueByAssetClassAxis" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_1AE11C84307B404BF93A755A8D0AA764" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A68D8311176AD48DF0A3755A8CF12EF9" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_1AE11C84307B404BF93A755A8D0AA764" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_D196ECE259A8BF66E274755A8D100F85_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_1AE11C84307B404BF93A755A8D0AA764" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_D196ECE259A8BF66E274755A8D100F85_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_D196ECE259A8BF66E274755A8D100F85" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_1AE11C84307B404BF93A755A8D0AA764" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_D196ECE259A8BF66E274755A8D100F85" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MoneyMarketFundsMember" xlink:label="loc_us-gaap_MoneyMarketFundsMember_0835C096FA5F5D93FFE5755A8D2E4266" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_D196ECE259A8BF66E274755A8D100F85" xlink:to="loc_us-gaap_MoneyMarketFundsMember_0835C096FA5F5D93FFE5755A8D2E4266" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_BBA53E865186DF467D33755A8CF1D4B3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A68D8311176AD48DF0A3755A8CF12EF9" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_BBA53E865186DF467D33755A8CF1D4B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_65A8C6E73F263689A3CA755A8CF23FC8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_BBA53E865186DF467D33755A8CF1D4B3" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_65A8C6E73F263689A3CA755A8CF23FC8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_65A8C6E73F263689A3CA755A8CF23FC8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_BBA53E865186DF467D33755A8CF1D4B3" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_65A8C6E73F263689A3CA755A8CF23FC8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_57E2FC741FA3B69E7B25755A8D3822DE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_65A8C6E73F263689A3CA755A8CF23FC8" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_57E2FC741FA3B69E7B25755A8D3822DE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_3ADE6ADB9BE30943C421755A8CF3DFAF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A68D8311176AD48DF0A3755A8CF12EF9" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_3ADE6ADB9BE30943C421755A8CF3DFAF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_51E5E107DB4308764B00755A8CF3A587_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_3ADE6ADB9BE30943C421755A8CF3DFAF" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_51E5E107DB4308764B00755A8CF3A587_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_51E5E107DB4308764B00755A8CF3A587" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_3ADE6ADB9BE30943C421755A8CF3DFAF" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_51E5E107DB4308764B00755A8CF3A587" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_9D892A8DED6E65181185755A8D24CF45" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_51E5E107DB4308764B00755A8CF3A587" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_9D892A8DED6E65181185755A8D24CF45" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AssetsFairValueDisclosure" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_1120CE4239203D3CD6C4755A8D0024A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_DFD1218431A9AB36DD7B755A8CF30C79" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_1120CE4239203D3CD6C4755A8D0024A4" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/GenzymeCoPromotionAgreement" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/GenzymeCoPromotionAgreementDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems" xlink:label="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable" xlink:label="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_B4609E96685A420E69DA6C7AFA25E78B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_B4609E96685A420E69DA6C7AFA25E78B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="loc_us-gaap_TypeOfArrangementAxis_F45EEC60ACC533BE75CF6C7AFA2507FD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_B4609E96685A420E69DA6C7AFA25E78B" xlink:to="loc_us-gaap_TypeOfArrangementAxis_F45EEC60ACC533BE75CF6C7AFA2507FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_2C707D2946153131F5256C7AFA256F9E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_F45EEC60ACC533BE75CF6C7AFA2507FD" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_2C707D2946153131F5256C7AFA256F9E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_2C707D2946153131F5256C7AFA256F9E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_F45EEC60ACC533BE75CF6C7AFA2507FD" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_2C707D2946153131F5256C7AFA256F9E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CollaborativeArrangementCopromotionMember" xlink:label="loc_us-gaap_CollaborativeArrangementCopromotionMember_592804A7E8841E6204426C7AFA255F5F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_2C707D2946153131F5256C7AFA256F9E" xlink:to="loc_us-gaap_CollaborativeArrangementCopromotionMember_592804A7E8841E6204426C7AFA255F5F" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CollaborativeArrangementCopromotionAfirmaThyroidDiagnosticSolutionMember" xlink:label="loc_vcyt_CollaborativeArrangementCopromotionAfirmaThyroidDiagnosticSolutionMember_DA19A3212675822BE9F26C7AFA25EAA2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_2C707D2946153131F5256C7AFA256F9E" xlink:to="loc_vcyt_CollaborativeArrangementCopromotionAfirmaThyroidDiagnosticSolutionMember_DA19A3212675822BE9F26C7AFA25EAA2" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CollaborativeArrangementCopromotionAfirmaGecMember" xlink:label="loc_vcyt_CollaborativeArrangementCopromotionAfirmaGecMember_BA8265EBF9FA7DE98C6D6C7AFA252CBD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_2C707D2946153131F5256C7AFA256F9E" xlink:to="loc_vcyt_CollaborativeArrangementCopromotionAfirmaGecMember_BA8265EBF9FA7DE98C6D6C7AFA252CBD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_64535C27BD32B2B296126C7AFA25B21D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_B4609E96685A420E69DA6C7AFA25E78B" xlink:to="loc_us-gaap_CounterpartyNameAxis_64535C27BD32B2B296126C7AFA25B21D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_0C2623D92A4D3241E7306C7AFA26A7C3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_64535C27BD32B2B296126C7AFA25B21D" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_0C2623D92A4D3241E7306C7AFA26A7C3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_0C2623D92A4D3241E7306C7AFA26A7C3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_64535C27BD32B2B296126C7AFA25B21D" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_0C2623D92A4D3241E7306C7AFA26A7C3" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_GenzymeCorporationMember" xlink:label="loc_vcyt_GenzymeCorporationMember_400234CC2D7A914F2EFD6C7AFA263D06" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_0C2623D92A4D3241E7306C7AFA26A7C3" xlink:to="loc_vcyt_GenzymeCorporationMember_400234CC2D7A914F2EFD6C7AFA263D06" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CollaborativeArrangementNumberOfCountriesOutsideUnitedStatesInWhichMarketingAuthorizationIsObtained" xlink:label="loc_vcyt_CollaborativeArrangementNumberOfCountriesOutsideUnitedStatesInWhichMarketingAuthorizationIsObtained_651683AD63D71A6F20FA6C7AFA261E67" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_vcyt_CollaborativeArrangementNumberOfCountriesOutsideUnitedStatesInWhichMarketingAuthorizationIsObtained_651683AD63D71A6F20FA6C7AFA261E67" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredRevenue" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_F08D2A57ADFE5B06A07D6C7AFA26029D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_F08D2A57ADFE5B06A07D6C7AFA26029D" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CollaborativeArrangementCoPromotionFeesPercentageOfCashReceipts" xlink:label="loc_vcyt_CollaborativeArrangementCoPromotionFeesPercentageOfCashReceipts_75BA7FE944975A1D48636C7AFA26B361" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_vcyt_CollaborativeArrangementCoPromotionFeesPercentageOfCashReceipts_75BA7FE944975A1D48636C7AFA26B361" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CollaborativeArrangementCoPromotionFeeAmortizationPeriod" xlink:label="loc_vcyt_CollaborativeArrangementCoPromotionFeeAmortizationPeriod_C64FA4A498075574156C6C7AFA26982D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_vcyt_CollaborativeArrangementCoPromotionFeeAmortizationPeriod_C64FA4A498075574156C6C7AFA26982D" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CollaborativeArrangementCoPromotionFeesPercentageOfNetRevenue" xlink:label="loc_vcyt_CollaborativeArrangementCoPromotionFeesPercentageOfNetRevenue_C00406D6E5CB651600E96C7AFA268A8F" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_vcyt_CollaborativeArrangementCoPromotionFeesPercentageOfNetRevenue_C00406D6E5CB651600E96C7AFA268A8F" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CollaborativeArrangementTerm" xlink:label="loc_vcyt_CollaborativeArrangementTerm_0BF12E708F6E995292FF6C7AFA263CD5" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_vcyt_CollaborativeArrangementTerm_0BF12E708F6E995292FF6C7AFA263CD5" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_AgreementTerminationNotice" xlink:label="loc_vcyt_AgreementTerminationNotice_B782104CB674A5FB575C6C7AFA2690B2" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_vcyt_AgreementTerminationNotice_B782104CB674A5FB575C6C7AFA2690B2" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CollaborativeArrangementCoPromotionExpenses" xlink:label="loc_vcyt_CollaborativeArrangementCoPromotionExpenses_CDFB9D2D42DF92081A7A6C7AFA26B44B" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_vcyt_CollaborativeArrangementCoPromotionExpenses_CDFB9D2D42DF92081A7A6C7AFA26B44B" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CollaborativeArrangementOutstandingObligation" xlink:label="loc_vcyt_CollaborativeArrangementOutstandingObligation_F51941780FBB9938833B6C7AFA2659F4" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_vcyt_CollaborativeArrangementOutstandingObligation_F51941780FBB9938833B6C7AFA2659F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RecognitionOfDeferredRevenue" xlink:label="loc_us-gaap_RecognitionOfDeferredRevenue_05F236A94CAB0C30D1A06C7AFA26AFAD" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_69862EE4F09EC252A4576C7AFA26C113" xlink:to="loc_us-gaap_RecognitionOfDeferredRevenue_05F236A94CAB0C30D1A06C7AFA26AFAD" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/IncomeTaxes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/IncomeTaxesIncomeTaxExaminationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxExaminationLineItems" xlink:label="loc_us-gaap_IncomeTaxExaminationLineItems_D2D79F507506689D3386888CE4C394CB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxExaminationTable" xlink:label="loc_us-gaap_IncomeTaxExaminationTable_B3F6A94A3E5582F2DC4D888CE4C20F30" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeTaxExaminationLineItems_D2D79F507506689D3386888CE4C394CB" xlink:to="loc_us-gaap_IncomeTaxExaminationTable_B3F6A94A3E5582F2DC4D888CE4C20F30" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_1F5C02AD8315E408986E888CE4C2C639" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxExaminationTable_B3F6A94A3E5582F2DC4D888CE4C20F30" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_1F5C02AD8315E408986E888CE4C2C639" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_7EDF16CBFCB3B092F71F888CE4C2B818_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_1F5C02AD8315E408986E888CE4C2C639" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_7EDF16CBFCB3B092F71F888CE4C2B818_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_7EDF16CBFCB3B092F71F888CE4C2B818" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_1F5C02AD8315E408986E888CE4C2C639" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_7EDF16CBFCB3B092F71F888CE4C2B818" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DomesticCountryMember" xlink:label="loc_us-gaap_DomesticCountryMember_F4B5AB8783172D0B7243888CE4C21423" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_7EDF16CBFCB3B092F71F888CE4C2B818" xlink:to="loc_us-gaap_DomesticCountryMember_F4B5AB8783172D0B7243888CE4C21423" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StateAndLocalJurisdictionMember" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_729AC39F67383A4ADDA2888CE4C336FF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_7EDF16CBFCB3B092F71F888CE4C2B818" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_729AC39F67383A4ADDA2888CE4C336FF" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_IncomeTaxExaminationPeriod" xlink:label="loc_vcyt_IncomeTaxExaminationPeriod_8FF2295F09E50801F90E888CE4C30FF2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExaminationLineItems_D2D79F507506689D3386888CE4C394CB" xlink:to="loc_vcyt_IncomeTaxExaminationPeriod_8FF2295F09E50801F90E888CE4C30FF2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/IncomeTaxesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/IncomeTaxesTaxEffectsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLossCarryforwardsLineItems" xlink:label="loc_us-gaap_OperatingLossCarryforwardsLineItems_84F951FA545D3398F56F24A41827A0DB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLossCarryforwardsTable" xlink:label="loc_us-gaap_OperatingLossCarryforwardsTable_A766009E0C6FC526576C24A41826C5E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_84F951FA545D3398F56F24A41827A0DB" xlink:to="loc_us-gaap_OperatingLossCarryforwardsTable_A766009E0C6FC526576C24A41826C5E0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_B43CA358DB3FCF07888824A41826E8FD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_A766009E0C6FC526576C24A41826C5E0" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_B43CA358DB3FCF07888824A41826E8FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_6B26AFB3D5EAE30089E724A41826B6F0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_B43CA358DB3FCF07888824A41826E8FD" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_6B26AFB3D5EAE30089E724A41826B6F0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_6B26AFB3D5EAE30089E724A41826B6F0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_B43CA358DB3FCF07888824A41826E8FD" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_6B26AFB3D5EAE30089E724A41826B6F0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DomesticCountryMember" xlink:label="loc_us-gaap_DomesticCountryMember_5DAC7D720581BD68DABB24A41826DF91" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_6B26AFB3D5EAE30089E724A41826B6F0" xlink:to="loc_us-gaap_DomesticCountryMember_5DAC7D720581BD68DABB24A41826DF91" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StateAndLocalJurisdictionMember" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_8784C73D3B2F2A4EC01B24A41827753C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_6B26AFB3D5EAE30089E724A41826B6F0" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_8784C73D3B2F2A4EC01B24A41827753C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLossCarryforwards" xlink:label="loc_us-gaap_OperatingLossCarryforwards_BE83745A059C8E89114524A4182760A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_84F951FA545D3398F56F24A41827A0DB" xlink:to="loc_us-gaap_OperatingLossCarryforwards_BE83745A059C8E89114524A4182760A4" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_OperatingLossCarryforwardsStockBasedCompensation" xlink:label="loc_vcyt_OperatingLossCarryforwardsStockBasedCompensation_5AE038DB8033F2020E0524A418272BF0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_84F951FA545D3398F56F24A41827A0DB" xlink:to="loc_vcyt_OperatingLossCarryforwardsStockBasedCompensation_5AE038DB8033F2020E0524A418272BF0" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TaxCreditCarryforwardLineItems" xlink:label="loc_us-gaap_TaxCreditCarryforwardLineItems_00710BFD17DFE7234D137533C731442F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TaxCreditCarryforwardTable" xlink:label="loc_us-gaap_TaxCreditCarryforwardTable_E4DB761F2A36FBA4F3337533C73119FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_00710BFD17DFE7234D137533C731442F" xlink:to="loc_us-gaap_TaxCreditCarryforwardTable_E4DB761F2A36FBA4F3337533C73119FB" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_5542FAE7A6F50EF354B57533C7315B19" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TaxCreditCarryforwardTable_E4DB761F2A36FBA4F3337533C73119FB" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_5542FAE7A6F50EF354B57533C7315B19" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_C2C89FC81247270B02797533C7312C32_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_5542FAE7A6F50EF354B57533C7315B19" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_C2C89FC81247270B02797533C7312C32_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_C2C89FC81247270B02797533C7312C32" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_5542FAE7A6F50EF354B57533C7315B19" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_C2C89FC81247270B02797533C7312C32" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DomesticCountryMember" xlink:label="loc_us-gaap_DomesticCountryMember_FED823D80BB9CAC193D77533C731BE01" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_C2C89FC81247270B02797533C7312C32" xlink:to="loc_us-gaap_DomesticCountryMember_FED823D80BB9CAC193D77533C731BE01" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StateAndLocalJurisdictionMember" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_8DE1124E0CC966D691507533C7318836" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_C2C89FC81247270B02797533C7312C32" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_8DE1124E0CC966D691507533C7318836" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TaxCreditCarryforwardAmount" xlink:label="loc_us-gaap_TaxCreditCarryforwardAmount_F8707991587AB1CCA8BE7533C7312C0E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_00710BFD17DFE7234D137533C731442F" xlink:to="loc_us-gaap_TaxCreditCarryforwardAmount_F8707991587AB1CCA8BE7533C7312C0E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ReconciliationOfUnrecognizedTaxBenefitsExcludingAmountsPertainingToExaminedTaxReturnsRollForward" xlink:label="loc_us-gaap_ReconciliationOfUnrecognizedTaxBenefitsExcludingAmountsPertainingToExaminedTaxReturnsRollForward_83BCC39D89195A6B14587533C731CE80" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_00710BFD17DFE7234D137533C731442F" xlink:to="loc_us-gaap_ReconciliationOfUnrecognizedTaxBenefitsExcludingAmountsPertainingToExaminedTaxReturnsRollForward_83BCC39D89195A6B14587533C731CE80" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_UnrecognizedTaxBenefits" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_E6AE98DD00FEC1BA53DC7533C731ADC6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReconciliationOfUnrecognizedTaxBenefitsExcludingAmountsPertainingToExaminedTaxReturnsRollForward_83BCC39D89195A6B14587533C731CE80" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_E6AE98DD00FEC1BA53DC7533C731ADC6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions_55334EEEC4830BBE099B7533C7319245" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReconciliationOfUnrecognizedTaxBenefitsExcludingAmountsPertainingToExaminedTaxReturnsRollForward_83BCC39D89195A6B14587533C731CE80" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions_55334EEEC4830BBE099B7533C7319245" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions_3E62D777A5B29A41116C7533C731BAB7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReconciliationOfUnrecognizedTaxBenefitsExcludingAmountsPertainingToExaminedTaxReturnsRollForward_83BCC39D89195A6B14587533C731CE80" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions_3E62D777A5B29A41116C7533C731BAB7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense_9A46709DDE57F3A2DB467533C7321C72" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_00710BFD17DFE7234D137533C731442F" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense_9A46709DDE57F3A2DB467533C7321C72" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/InterestExpenseDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_C6163BBF1EDA09B656E07533C7827085" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_E539EF35D0C2C5F32B4B7533C782CDFD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C6163BBF1EDA09B656E07533C7827085" xlink:to="loc_us-gaap_DebtInstrumentTable_E539EF35D0C2C5F32B4B7533C782CDFD" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_53CBEA589BD44512954A7533C7826AF6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_E539EF35D0C2C5F32B4B7533C782CDFD" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_53CBEA589BD44512954A7533C7826AF6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_EF0DC3669EA1660B5B307533C782F2C7_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_53CBEA589BD44512954A7533C7826AF6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_EF0DC3669EA1660B5B307533C782F2C7_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_EF0DC3669EA1660B5B307533C782F2C7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_53CBEA589BD44512954A7533C7826AF6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_EF0DC3669EA1660B5B307533C782F2C7" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TermLoanMember" xlink:label="loc_vcyt_TermLoanMember_BE61E447B2E8B9E9BB317533C7824DF1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_EF0DC3669EA1660B5B307533C782F2C7" xlink:to="loc_vcyt_TermLoanMember_BE61E447B2E8B9E9BB317533C7824DF1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InterestExpenseDebtAbstract" xlink:label="loc_us-gaap_InterestExpenseDebtAbstract_E58A090F6A940BFCDDFA7533C78261F6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C6163BBF1EDA09B656E07533C7827085" xlink:to="loc_us-gaap_InterestExpenseDebtAbstract_E58A090F6A940BFCDDFA7533C78261F6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InterestExpenseDebtExcludingAmortization" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization_473B3FB5C06B8D7D0EF57533C78292A5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseDebtAbstract_E58A090F6A940BFCDDFA7533C78261F6" xlink:to="loc_us-gaap_InterestExpenseDebtExcludingAmortization_473B3FB5C06B8D7D0EF57533C78292A5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:label="loc_us-gaap_AmortizationOfDebtDiscountPremium_62FE5B0D5B4D0D95D4A67533C782D9FD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseDebtAbstract_E58A090F6A940BFCDDFA7533C78261F6" xlink:to="loc_us-gaap_AmortizationOfDebtDiscountPremium_62FE5B0D5B4D0D95D4A67533C782D9FD" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_DebtInstrumentEndOfTermPaymentInterestAmount" xlink:label="loc_vcyt_DebtInstrumentEndOfTermPaymentInterestAmount_3E051438C2D2DBA74C927533C7821B9A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseDebtAbstract_E58A090F6A940BFCDDFA7533C78261F6" xlink:to="loc_vcyt_DebtInstrumentEndOfTermPaymentInterestAmount_3E051438C2D2DBA74C927533C7821B9A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InterestExpenseDebt" xlink:label="loc_us-gaap_InterestExpenseDebt_4EF1202996E14BBC8DB77533C782AFE8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseDebtAbstract_E58A090F6A940BFCDDFA7533C78261F6" xlink:to="loc_us-gaap_InterestExpenseDebt_4EF1202996E14BBC8DB77533C782AFE8" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/NetLossPerShare" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/NetLossPerShareDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_9C7D7A2545343E80B57F3F845EB1E84A" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_003022B783212492AAA13F845EADC6B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_9C7D7A2545343E80B57F3F845EB1E84A" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_003022B783212492AAA13F845EADC6B2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_A6E8F11B9355093390483F845EAD608B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_003022B783212492AAA13F845EADC6B2" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_A6E8F11B9355093390483F845EAD608B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_E4B416B49860BDADBB3E3F845EAEEF04_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_A6E8F11B9355093390483F845EAD608B" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_E4B416B49860BDADBB3E3F845EAEEF04_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_E4B416B49860BDADBB3E3F845EAEEF04" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_A6E8F11B9355093390483F845EAD608B" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_E4B416B49860BDADBB3E3F845EAEEF04" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_EmployeeAndNonEmployeeStockOptionMember" xlink:label="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_83F2A491A3A2DA24A5E73F845EAE129C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_E4B416B49860BDADBB3E3F845EAEEF04" xlink:to="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_83F2A491A3A2DA24A5E73F845EAE129C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityUnitPurchaseAgreementsMember" xlink:label="loc_us-gaap_EquityUnitPurchaseAgreementsMember_DC8B2F0D823E83BAFB3B3F845EAF5E79" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_E4B416B49860BDADBB3E3F845EAEEF04" xlink:to="loc_us-gaap_EquityUnitPurchaseAgreementsMember_DC8B2F0D823E83BAFB3B3F845EAF5E79" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_E7DE74D25EDCDE00C5BE3F853245411D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_E4B416B49860BDADBB3E3F845EAEEF04" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_E7DE74D25EDCDE00C5BE3F853245411D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_3F933628461FB87BF6CF3F845EB1177F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_9C7D7A2545343E80B57F3F845EB1E84A" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_3F933628461FB87BF6CF3F845EB1177F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/NetLossPerShareTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/OrganizationAndDescriptionOfBusiness" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/SelectedQuarterlyFinancialDataUnaudited" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/SelectedQuarterlyFinancialDataUnauditedDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/SelectedQuarterlyFinancialDataUnauditedTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StatementsOfCashFlows" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StatementsOfOperationsAndComprehensiveLoss" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StatementsOfStockholdersEquity" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_C35191F0679236D32E966C1DB8A5498A" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_CEF9C7C3A74EEDEFE9806C1DB8A547A6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_C35191F0679236D32E966C1DB8A5498A" xlink:to="loc_us-gaap_StatementTable_CEF9C7C3A74EEDEFE9806C1DB8A547A6" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_AA81B462BAD90E19D9AC6C1DB8A52C47" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_CEF9C7C3A74EEDEFE9806C1DB8A547A6" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_AA81B462BAD90E19D9AC6C1DB8A52C47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_E2E666D8CDC372D2F2D16C1DB8A58D0C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_AA81B462BAD90E19D9AC6C1DB8A52C47" xlink:to="loc_us-gaap_EquityComponentDomain_E2E666D8CDC372D2F2D16C1DB8A58D0C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_E2E666D8CDC372D2F2D16C1DB8A58D0C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_AA81B462BAD90E19D9AC6C1DB8A52C47" xlink:to="loc_us-gaap_EquityComponentDomain_E2E666D8CDC372D2F2D16C1DB8A58D0C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_90427A7368B5CEAD8CDC6C1DB8A5F7AE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_E2E666D8CDC372D2F2D16C1DB8A58D0C" xlink:to="loc_us-gaap_CommonStockMember_90427A7368B5CEAD8CDC6C1DB8A5F7AE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_6694D14C92F9D36D08FB6C1DB8A59248" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_E2E666D8CDC372D2F2D16C1DB8A58D0C" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_6694D14C92F9D36D08FB6C1DB8A59248" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaap_RetainedEarningsMember_EA8038B4C3F4F9EDDE496C1DB8A528CE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_E2E666D8CDC372D2F2D16C1DB8A58D0C" xlink:to="loc_us-gaap_RetainedEarningsMember_EA8038B4C3F4F9EDDE496C1DB8A528CE" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward" xlink:label="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_C35191F0679236D32E966C1DB8A5498A" xlink:to="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_1B8159BA0ED5C3817E866C1DB8A6B242" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_us-gaap_StockholdersEquity_1B8159BA0ED5C3817E866C1DB8A6B242" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharesOutstanding" xlink:label="loc_us-gaap_SharesOutstanding_4B462FB906B34EB4A13F6C1DB8A67267" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_us-gaap_SharesOutstanding_4B462FB906B34EB4A13F6C1DB8A67267" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_4895BF4578A3179820FC6C1DB8A63A90" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_4895BF4578A3179820FC6C1DB8A63A90" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_8B10B78064A88CC764486C1DB8A6536D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_4895BF4578A3179820FC6C1DB8A63A90" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_8B10B78064A88CC764486C1DB8A6536D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_0F8813CA9EF4E7AE60216C1DB8A6983A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_0F8813CA9EF4E7AE60216C1DB8A6983A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_C4FB6A3A691EAE882C556C1DB8A65A90" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_0F8813CA9EF4E7AE60216C1DB8A6983A" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_C4FB6A3A691EAE882C556C1DB8A65A90" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockIssuedDuringPeriodSharesWarrantsExercised" xlink:label="loc_vcyt_StockIssuedDuringPeriodSharesWarrantsExercised_EADC6649CE99FD6B963E6C1DB8A67AAF" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_vcyt_StockIssuedDuringPeriodSharesWarrantsExercised_EADC6649CE99FD6B963E6C1DB8A67AAF" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_AdjustmentsToAdditionalPaidInCapitalCommonStockSubjectToRepurchase" xlink:label="loc_vcyt_AdjustmentsToAdditionalPaidInCapitalCommonStockSubjectToRepurchase_AC40688F944D376050336C1DB8A685C5" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_vcyt_AdjustmentsToAdditionalPaidInCapitalCommonStockSubjectToRepurchase_AC40688F944D376050336C1DB8A685C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_560761935CB7AB68FF9F6C1DB8A6CF06" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_560761935CB7AB68FF9F6C1DB8A6CF06" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_E8D6346A66507741868F6C1DB8A6A526" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_560761935CB7AB68FF9F6C1DB8A6CF06" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_E8D6346A66507741868F6C1DB8A6A526" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockIssuedAndSoldDuringPeriodValueInPrivatePlacement" xlink:label="loc_vcyt_StockIssuedAndSoldDuringPeriodValueInPrivatePlacement_638A5D864369C77A7B446C1DB8A66B4F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_vcyt_StockIssuedAndSoldDuringPeriodValueInPrivatePlacement_638A5D864369C77A7B446C1DB8A66B4F" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockIssuedAndSoldDuringPeriodSharesInPrivatePlacement" xlink:label="loc_vcyt_StockIssuedAndSoldDuringPeriodSharesInPrivatePlacement_F95A97340BADDF5DAEA76C1DB8A69C60" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_StockIssuedAndSoldDuringPeriodValueInPrivatePlacement_638A5D864369C77A7B446C1DB8A66B4F" xlink:to="loc_vcyt_StockIssuedAndSoldDuringPeriodSharesInPrivatePlacement_F95A97340BADDF5DAEA76C1DB8A69C60" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CommonStockIssuedIssuanceCostsPrivatePlacement" xlink:label="loc_vcyt_CommonStockIssuedIssuanceCostsPrivatePlacement_46588BABA366BF6850216C1DB8A60EC0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_StockIssuedAndSoldDuringPeriodValueInPrivatePlacement_638A5D864369C77A7B446C1DB8A66B4F" xlink:to="loc_vcyt_CommonStockIssuedIssuanceCostsPrivatePlacement_46588BABA366BF6850216C1DB8A60EC0" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationEmployee" xlink:label="loc_vcyt_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationEmployee_4968C7DECBC2B47BEC646C1DB8A6DCBF" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_vcyt_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationEmployee_4968C7DECBC2B47BEC646C1DB8A6DCBF" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationNonEmployee" xlink:label="loc_vcyt_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationNonEmployee_3FBBB634FD1D085E83546C1DB8A69771" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_vcyt_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationNonEmployee_3FBBB634FD1D085E83546C1DB8A69771" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationESPP" xlink:label="loc_vcyt_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationESPP_856F46C268C1C51AE0CC6C1DB8A76212" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_vcyt_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationESPP_856F46C268C1C51AE0CC6C1DB8A76212" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_9CF3219DDD73C274F1F86C1DB8A76529" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_9CF3219DDD73C274F1F86C1DB8A76529" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_A95F7C61DB80434DEA896C1DB8A7083A" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_IncreaseDecreaseInConvertiblePreferredStockAndStockholdersEquityRollForward_2A87BEAFBD5F2A59A1146C1DB8A56947" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_A95F7C61DB80434DEA896C1DB8A7083A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StockIncentivePlans" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StockIncentivePlansActivityUnderStockOptionPlansDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8B3FFD03E322E4A8485881D00CB8CB1C" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_97FFC337BEAB4D54319381D00CB8088F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8B3FFD03E322E4A8485881D00CB8CB1C" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_97FFC337BEAB4D54319381D00CB8088F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_3E72C892CA1404F1C35A81D00CB89B27" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_97FFC337BEAB4D54319381D00CB8088F" xlink:to="loc_us-gaap_AwardTypeAxis_3E72C892CA1404F1C35A81D00CB89B27" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4105A825ED76298BA34781D00CB8B0B6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_3E72C892CA1404F1C35A81D00CB89B27" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4105A825ED76298BA34781D00CB8B0B6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4105A825ED76298BA34781D00CB8B0B6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_3E72C892CA1404F1C35A81D00CB89B27" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4105A825ED76298BA34781D00CB8B0B6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_828AD17A75E49DA138FC81D00CB80D2D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4105A825ED76298BA34781D00CB8B0B6" xlink:to="loc_us-gaap_EmployeeStockOptionMember_828AD17A75E49DA138FC81D00CB80D2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_66F4ED5CF8220DE49EC681D00CB8917C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4105A825ED76298BA34781D00CB8B0B6" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_66F4ED5CF8220DE49EC681D00CB8917C" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward_8DEE19630739E4AEDD0681D00CB8D171" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8B3FFD03E322E4A8485881D00CB8CB1C" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward_8DEE19630739E4AEDD0681D00CB8D171" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_2E304B8FC9D1CBF23D5E81D00CB8FCE4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward_8DEE19630739E4AEDD0681D00CB8D171" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_2E304B8FC9D1CBF23D5E81D00CB8FCE4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_637A54919A5FDAA13E7B81D00CB8C20B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward_8DEE19630739E4AEDD0681D00CB8D171" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_637A54919A5FDAA13E7B81D00CB8C20B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_800B9D854BA69EC90A6B81D00CB800E5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward_8DEE19630739E4AEDD0681D00CB8D171" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_800B9D854BA69EC90A6B81D00CB800E5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_12806445DE90B218670881D00CB8262D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward_8DEE19630739E4AEDD0681D00CB8D171" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_12806445DE90B218670881D00CB8262D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_B15800205C396CBFCBDA81D00CB9E7D1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8B3FFD03E322E4A8485881D00CB8CB1C" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_B15800205C396CBFCBDA81D00CB9E7D1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_BF82E37F794909BBE29081D00CB965A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_B15800205C396CBFCBDA81D00CB9E7D1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_BF82E37F794909BBE29081D00CB965A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_7C63F4689A271132CDD081D00CB9AE4E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_B15800205C396CBFCBDA81D00CB9E7D1" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_7C63F4689A271132CDD081D00CB9AE4E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_E8FADE19A8256B18C8CA81D00CB90026" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_B15800205C396CBFCBDA81D00CB9E7D1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_E8FADE19A8256B18C8CA81D00CB90026" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_A6240B18BE0933A447A481D00CB98BE6" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_B15800205C396CBFCBDA81D00CB9E7D1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_A6240B18BE0933A447A481D00CB98BE6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_E8DE9209966E118AFF3381D00CB9C307" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8B3FFD03E322E4A8485881D00CB8CB1C" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_E8DE9209966E118AFF3381D00CB9C307" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_10E20994FC05E0A4AE1A81D00CB95897" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_E8DE9209966E118AFF3381D00CB9C307" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_10E20994FC05E0A4AE1A81D00CB95897" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_85EF3BDBB59D7568FB1B81D00CBA503F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_E8DE9209966E118AFF3381D00CB9C307" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_85EF3BDBB59D7568FB1B81D00CBA503F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_F3C4F74BFFB3D00DACCD81D00CBAAF49" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_E8DE9209966E118AFF3381D00CB9C307" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_F3C4F74BFFB3D00DACCD81D00CBAAF49" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_B3CF7BD4C67B5148AEE981D00CBAA8DA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_E8DE9209966E118AFF3381D00CB9C307" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_B3CF7BD4C67B5148AEE981D00CBAA8DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_D17CCB46B56507B4562881D00CBA016A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_E8DE9209966E118AFF3381D00CB9C307" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_D17CCB46B56507B4562881D00CBA016A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_A6FFEA5968F0186C5D6281D00CBA7BDE" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_E8DE9209966E118AFF3381D00CB9C307" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_A6FFEA5968F0186C5D6281D00CBA7BDE" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract_AFD1A650F32639CD789E81D00CBA935F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8B3FFD03E322E4A8485881D00CB8CB1C" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract_AFD1A650F32639CD789E81D00CBA935F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_98BBE78E5D5981B562D081D00CBA6754" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract_AFD1A650F32639CD789E81D00CBA935F" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_98BBE78E5D5981B562D081D00CBA6754" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_2136269034639EBCD91281D00CBA8FEB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract_AFD1A650F32639CD789E81D00CBA935F" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_2136269034639EBCD91281D00CBA8FEB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_7E43C156F19A3CDE585981D00CBAE219" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract_AFD1A650F32639CD789E81D00CBA935F" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_7E43C156F19A3CDE585981D00CBAE219" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract_30E6D50BDEF37862E6B981D00CBA749E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8B3FFD03E322E4A8485881D00CB8CB1C" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract_30E6D50BDEF37862E6B981D00CBA749E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_3F60DA7237BD2A0F9AE081D00CBAD34D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract_30E6D50BDEF37862E6B981D00CBA749E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_3F60DA7237BD2A0F9AE081D00CBAD34D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_D93995DC747BE50DC12381D00CBA2D9D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract_30E6D50BDEF37862E6B981D00CBA749E" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_D93995DC747BE50DC12381D00CBA2D9D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_30E9B87A23549D6BB56881D00CBA18D7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract_30E6D50BDEF37862E6B981D00CBA749E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_30E9B87A23549D6BB56881D00CBA18D7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StockIncentivePlansAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5B197D3840E968CE378C24A4184DC4F2" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D5B256956C7439154D8E24A4184CB535" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5B197D3840E968CE378C24A4184DC4F2" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D5B256956C7439154D8E24A4184CB535" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_17DF047E903090451F3324A4184C6CD8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D5B256956C7439154D8E24A4184CB535" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_17DF047E903090451F3324A4184C6CD8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_1CD62C4AA7116DC0560724A4184C7A25_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_17DF047E903090451F3324A4184C6CD8" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_1CD62C4AA7116DC0560724A4184C7A25_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_1CD62C4AA7116DC0560724A4184C7A25" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_17DF047E903090451F3324A4184C6CD8" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_1CD62C4AA7116DC0560724A4184C7A25" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_EDDA0DF670F56EBB3D9624A4184CFC1E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D5B256956C7439154D8E24A4184CB535" xlink:to="loc_us-gaap_AwardTypeAxis_EDDA0DF670F56EBB3D9624A4184CFC1E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_29CBE0DD87ADAED2CA2D24A4184CC395_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_EDDA0DF670F56EBB3D9624A4184CFC1E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_29CBE0DD87ADAED2CA2D24A4184CC395_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_29CBE0DD87ADAED2CA2D24A4184CC395" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_EDDA0DF670F56EBB3D9624A4184CFC1E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_29CBE0DD87ADAED2CA2D24A4184CC395" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_0AF284DC2B05BC7FFD8924A4184CD07D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_29CBE0DD87ADAED2CA2D24A4184CC395" xlink:to="loc_us-gaap_EmployeeStockOptionMember_0AF284DC2B05BC7FFD8924A4184CD07D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_523A8E6128F55EF4BFD524A4184D54F3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D5B256956C7439154D8E24A4184CB535" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_523A8E6128F55EF4BFD524A4184D54F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_C6CE260ADB7F89ADF7AC24A4184DDE56_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_523A8E6128F55EF4BFD524A4184D54F3" xlink:to="loc_us-gaap_EquityComponentDomain_C6CE260ADB7F89ADF7AC24A4184DDE56_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_C6CE260ADB7F89ADF7AC24A4184DDE56" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_523A8E6128F55EF4BFD524A4184D54F3" xlink:to="loc_us-gaap_EquityComponentDomain_C6CE260ADB7F89ADF7AC24A4184DDE56" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_68A0EEA47340AC0A8E7524A4184DEFF2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_C6CE260ADB7F89ADF7AC24A4184DDE56" xlink:to="loc_us-gaap_CommonStockMember_68A0EEA47340AC0A8E7524A4184DEFF2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharePrice" xlink:label="loc_us-gaap_SharePrice_E963A622346FFA9DE4A224A4184DA923" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5B197D3840E968CE378C24A4184DC4F2" xlink:to="loc_us-gaap_SharePrice_E963A622346FFA9DE4A224A4184DA923" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_D2211D2E787D77816F9824A4184DEF95" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5B197D3840E968CE378C24A4184DC4F2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_D2211D2E787D77816F9824A4184DEF95" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_DF11B56CA963D670B91624A4184D6247" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5B197D3840E968CE378C24A4184DC4F2" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_DF11B56CA963D670B91624A4184D6247" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_49FAD461FC246A0FC3D324A4184D5B87" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5B197D3840E968CE378C24A4184DC4F2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_49FAD461FC246A0FC3D324A4184D5B87" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_3C7F470CE1FAB722899024A4184DA6EC" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5B197D3840E968CE378C24A4184DC4F2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_3C7F470CE1FAB722899024A4184DA6EC" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StockIncentivePlansStockBasedCompensationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_C90C41BEFC91EE1430AB8742380492B1" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_B2083B6B461DE577AFB08742380157F1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_C90C41BEFC91EE1430AB8742380492B1" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_B2083B6B461DE577AFB08742380157F1" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_E5305227225D148A95D58742380203FA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_B2083B6B461DE577AFB08742380157F1" xlink:to="loc_us-gaap_PlanNameAxis_E5305227225D148A95D58742380203FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_9DB7EE55592E16EE7DE5874238026B53_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_E5305227225D148A95D58742380203FA" xlink:to="loc_us-gaap_PlanNameDomain_9DB7EE55592E16EE7DE5874238026B53_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_9DB7EE55592E16EE7DE5874238026B53" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_E5305227225D148A95D58742380203FA" xlink:to="loc_us-gaap_PlanNameDomain_9DB7EE55592E16EE7DE5874238026B53" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockPlan2008Member" xlink:label="loc_vcyt_StockPlan2008Member_911845F4DE5E04E9B00C8742380217D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_9DB7EE55592E16EE7DE5874238026B53" xlink:to="loc_vcyt_StockPlan2008Member_911845F4DE5E04E9B00C8742380217D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_7371E1BDB84FF2D7034B874238029F78" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_B2083B6B461DE577AFB08742380157F1" xlink:to="loc_us-gaap_RangeAxis_7371E1BDB84FF2D7034B874238029F78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_6238FF7FC151E5C446DB8742380206A4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_7371E1BDB84FF2D7034B874238029F78" xlink:to="loc_us-gaap_RangeMember_6238FF7FC151E5C446DB8742380206A4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_6238FF7FC151E5C446DB8742380206A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_7371E1BDB84FF2D7034B874238029F78" xlink:to="loc_us-gaap_RangeMember_6238FF7FC151E5C446DB8742380206A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_6D83D9B7012FA79074A087423803C08C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_6238FF7FC151E5C446DB8742380206A4" xlink:to="loc_us-gaap_MinimumMember_6D83D9B7012FA79074A087423803C08C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_0BE02BD951927620B6D7874238031B8C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_6238FF7FC151E5C446DB8742380206A4" xlink:to="loc_us-gaap_MaximumMember_0BE02BD951927620B6D7874238031B8C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_92E8E90ECF98CB03759487423803D85F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_B2083B6B461DE577AFB08742380157F1" xlink:to="loc_us-gaap_AwardTypeAxis_92E8E90ECF98CB03759487423803D85F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6105FEBBD9A638605773874238030C0A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_92E8E90ECF98CB03759487423803D85F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6105FEBBD9A638605773874238030C0A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6105FEBBD9A638605773874238030C0A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_92E8E90ECF98CB03759487423803D85F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6105FEBBD9A638605773874238030C0A" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_EmployeeAndNonEmployeeStockOptionMember" xlink:label="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_D15C6A2C3F644B6ABFF28742380318C0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6105FEBBD9A638605773874238030C0A" xlink:to="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_D15C6A2C3F644B6ABFF28742380318C0" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_IncentiveStockOptionsMember" xlink:label="loc_vcyt_IncentiveStockOptionsMember_9F7AD65DE5759888A37E874238033924" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6105FEBBD9A638605773874238030C0A" xlink:to="loc_vcyt_IncentiveStockOptionsMember_9F7AD65DE5759888A37E874238033924" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_EmployeeAndNonEmployeeStockOptionExcludingBonusCompensationMember" xlink:label="loc_vcyt_EmployeeAndNonEmployeeStockOptionExcludingBonusCompensationMember_A12240A5E5C600B6DC6A8742380381F6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6105FEBBD9A638605773874238030C0A" xlink:to="loc_vcyt_EmployeeAndNonEmployeeStockOptionExcludingBonusCompensationMember_A12240A5E5C600B6DC6A8742380381F6" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_EmployeeStockOptionExcludingBonusCompensationMember" xlink:label="loc_vcyt_EmployeeStockOptionExcludingBonusCompensationMember_6EDFA9598D4E3397295087423803A0B8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6105FEBBD9A638605773874238030C0A" xlink:to="loc_vcyt_EmployeeStockOptionExcludingBonusCompensationMember_6EDFA9598D4E3397295087423803A0B8" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_NonEmployeeStockOptionMember" xlink:label="loc_vcyt_NonEmployeeStockOptionMember_98130A2870267D50C1FA874238030E65" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6105FEBBD9A638605773874238030C0A" xlink:to="loc_vcyt_NonEmployeeStockOptionMember_98130A2870267D50C1FA874238030E65" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeStockMember" xlink:label="loc_us-gaap_EmployeeStockMember_47754B72444C96BF9211874238038516" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6105FEBBD9A638605773874238030C0A" xlink:to="loc_us-gaap_EmployeeStockMember_47754B72444C96BF9211874238038516" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_08999D21BC03228CF99F874238038BE4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_B2083B6B461DE577AFB08742380157F1" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_08999D21BC03228CF99F874238038BE4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_D8BD52268771A522B837874238044766_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_08999D21BC03228CF99F874238038BE4" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_D8BD52268771A522B837874238044766_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_D8BD52268771A522B837874238044766" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_08999D21BC03228CF99F874238038BE4" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_D8BD52268771A522B837874238044766" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CostOfSalesMember" xlink:label="loc_us-gaap_CostOfSalesMember_4BD9674F267B4545E270874238043787" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_D8BD52268771A522B837874238044766" xlink:to="loc_us-gaap_CostOfSalesMember_4BD9674F267B4545E270874238043787" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_B45A4FF4564F42252FCF8742380465AD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_D8BD52268771A522B837874238044766" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_B45A4FF4564F42252FCF8742380465AD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SellingAndMarketingExpenseMember" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_B859AC8EEFF89220C79E87423804845F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_D8BD52268771A522B837874238044766" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_B859AC8EEFF89220C79E87423804845F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_E08B33FA9D6DACE7A1B8874238042237" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_D8BD52268771A522B837874238044766" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_E08B33FA9D6DACE7A1B8874238042237" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermOfOptionsGrantedToEmployeesWhoOwnedSpecifiedPercentageOfClassOfStock" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermOfOptionsGrantedToEmployeesWhoOwnedSpecifiedPercentageOfClassOfStock_DF85502E752EFDCC756787423804FF59" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_C90C41BEFC91EE1430AB8742380492B1" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermOfOptionsGrantedToEmployeesWhoOwnedSpecifiedPercentageOfClassOfStock_DF85502E752EFDCC756787423804FF59" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_726688ECC977CDE7115E87423804B6A0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_C90C41BEFC91EE1430AB8742380492B1" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_726688ECC977CDE7115E87423804B6A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_5F0C62C75C33F92A788B87423804FAF1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_C90C41BEFC91EE1430AB8742380492B1" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_5F0C62C75C33F92A788B87423804FAF1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_DD06BCC704E0B183D8A0874238049867" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_C90C41BEFC91EE1430AB8742380492B1" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_DD06BCC704E0B183D8A0874238049867" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_6854AD9147F8B2D6FA0B8742380441FB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_C90C41BEFC91EE1430AB8742380492B1" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_6854AD9147F8B2D6FA0B8742380441FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_7CCC8F02EC0517FE63FD87423804548E" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_C90C41BEFC91EE1430AB8742380492B1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_7CCC8F02EC0517FE63FD87423804548E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_3B74B944E9DA7C72A51A87423804703F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_7CCC8F02EC0517FE63FD87423804548E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_3B74B944E9DA7C72A51A87423804703F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_09699798D1588EE6566A874238040A73" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_7CCC8F02EC0517FE63FD87423804548E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_09699798D1588EE6566A874238040A73" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_BD46D02000A19D5BEE77874238043D00" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_7CCC8F02EC0517FE63FD87423804548E" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_BD46D02000A19D5BEE77874238043D00" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_36C5FBF024FEFB2D061D874238059406" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_7CCC8F02EC0517FE63FD87423804548E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_36C5FBF024FEFB2D061D874238059406" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_6F2F82708432028DB5B687423805C705" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_7CCC8F02EC0517FE63FD87423804548E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_6F2F82708432028DB5B687423805C705" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StockIncentivePlansStockIncentivePlansEsppDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_AF0AE1F5C2A28C4DFECBCE08ED263143" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_11E6C883347D3B2108DCCE08ED186D7F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_AF0AE1F5C2A28C4DFECBCE08ED263143" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_11E6C883347D3B2108DCCE08ED186D7F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_651490CA9C7EE0CDA9D3CE08ED18E159" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_11E6C883347D3B2108DCCE08ED186D7F" xlink:to="loc_us-gaap_PlanNameAxis_651490CA9C7EE0CDA9D3CE08ED18E159" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_9EB5C72C8A01D630BCBBCE08ED1DE94F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_651490CA9C7EE0CDA9D3CE08ED18E159" xlink:to="loc_us-gaap_PlanNameDomain_9EB5C72C8A01D630BCBBCE08ED1DE94F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_9EB5C72C8A01D630BCBBCE08ED1DE94F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_651490CA9C7EE0CDA9D3CE08ED18E159" xlink:to="loc_us-gaap_PlanNameDomain_9EB5C72C8A01D630BCBBCE08ED1DE94F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardDateAxis" xlink:label="loc_us-gaap_AwardDateAxis_037B187D7FD0E019D2A2CE08ED1EDC58" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_11E6C883347D3B2108DCCE08ED186D7F" xlink:to="loc_us-gaap_AwardDateAxis_037B187D7FD0E019D2A2CE08ED1EDC58" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardDateDomain" xlink:label="loc_us-gaap_AwardDateDomain_2DFA1DC1824F18ECB2D9CE08ED1E3713_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardDateAxis_037B187D7FD0E019D2A2CE08ED1EDC58" xlink:to="loc_us-gaap_AwardDateDomain_2DFA1DC1824F18ECB2D9CE08ED1E3713_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardDateDomain" xlink:label="loc_us-gaap_AwardDateDomain_2DFA1DC1824F18ECB2D9CE08ED1E3713" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardDateAxis_037B187D7FD0E019D2A2CE08ED1EDC58" xlink:to="loc_us-gaap_AwardDateDomain_2DFA1DC1824F18ECB2D9CE08ED1E3713" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_03E779502488F41566B8CE08ED1E08A2" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_11E6C883347D3B2108DCCE08ED186D7F" xlink:to="loc_us-gaap_AwardTypeAxis_03E779502488F41566B8CE08ED1E08A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_463C9BDC0F6FC6B14C9ECE08ED1F2EE5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_03E779502488F41566B8CE08ED1E08A2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_463C9BDC0F6FC6B14C9ECE08ED1F2EE5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_463C9BDC0F6FC6B14C9ECE08ED1F2EE5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_03E779502488F41566B8CE08ED1E08A2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_463C9BDC0F6FC6B14C9ECE08ED1F2EE5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeStockMember" xlink:label="loc_us-gaap_EmployeeStockMember_6BD66386AD02D107FA1ECE08EE6D5123" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_463C9BDC0F6FC6B14C9ECE08ED1F2EE5" xlink:to="loc_us-gaap_EmployeeStockMember_6BD66386AD02D107FA1ECE08EE6D5123" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_FB962A777F7ACFC19003CE08ED1F4557" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_11E6C883347D3B2108DCCE08ED186D7F" xlink:to="loc_us-gaap_StatementClassOfStockAxis_FB962A777F7ACFC19003CE08ED1F4557" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_CD13398C2CE4FD3564E7CE08ED1F3F75_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_FB962A777F7ACFC19003CE08ED1F4557" xlink:to="loc_us-gaap_ClassOfStockDomain_CD13398C2CE4FD3564E7CE08ED1F3F75_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_CD13398C2CE4FD3564E7CE08ED1F3F75" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_FB962A777F7ACFC19003CE08ED1F4557" xlink:to="loc_us-gaap_ClassOfStockDomain_CD13398C2CE4FD3564E7CE08ED1F3F75" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_C8F03734C991ECD5EC34CE08ED25BDCE" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_11E6C883347D3B2108DCCE08ED186D7F" xlink:to="loc_us-gaap_RangeAxis_C8F03734C991ECD5EC34CE08ED25BDCE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_8CFFBDBD67FF62A218B1CE08ED251079_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_C8F03734C991ECD5EC34CE08ED25BDCE" xlink:to="loc_us-gaap_RangeMember_8CFFBDBD67FF62A218B1CE08ED251079_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_8CFFBDBD67FF62A218B1CE08ED251079" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_C8F03734C991ECD5EC34CE08ED25BDCE" xlink:to="loc_us-gaap_RangeMember_8CFFBDBD67FF62A218B1CE08ED251079" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_FBA7E5DB8BB4EF2B8428CE08EEA1A639" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_8CFFBDBD67FF62A218B1CE08ED251079" xlink:to="loc_us-gaap_MinimumMember_FBA7E5DB8BB4EF2B8428CE08EEA1A639" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_VestingAxis" xlink:label="loc_us-gaap_VestingAxis_1E74427C97182C1B115ACE08ED267DCE" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_11E6C883347D3B2108DCCE08ED186D7F" xlink:to="loc_us-gaap_VestingAxis_1E74427C97182C1B115ACE08ED267DCE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_VestingDomain" xlink:label="loc_us-gaap_VestingDomain_DC7D02B5E81FABED6B36CE08ED2675A7_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_1E74427C97182C1B115ACE08ED267DCE" xlink:to="loc_us-gaap_VestingDomain_DC7D02B5E81FABED6B36CE08ED2675A7_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_VestingDomain" xlink:label="loc_us-gaap_VestingDomain_DC7D02B5E81FABED6B36CE08ED2675A7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_1E74427C97182C1B115ACE08ED267DCE" xlink:to="loc_us-gaap_VestingDomain_DC7D02B5E81FABED6B36CE08ED2675A7" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriodMaximum" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriodMaximum_12F25AABE52C6FE90376CE08ED6E2AE9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_AF0AE1F5C2A28C4DFECBCE08ED263143" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriodMaximum_12F25AABE52C6FE90376CE08ED6E2AE9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_644F0CD89E5B781662CDCE08ED9D1D0A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_AF0AE1F5C2A28C4DFECBCE08ED263143" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_644F0CD89E5B781662CDCE08ED9D1D0A" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriod" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriod_57078BFE0469E6BE583FCE08EDCF0E6D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_AF0AE1F5C2A28C4DFECBCE08ED263143" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriod_57078BFE0469E6BE583FCE08EDCF0E6D" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumValueOfSharesPerEmployee" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumValueOfSharesPerEmployee_EE38327BE8F96D1BC860CE08EE005B15" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_AF0AE1F5C2A28C4DFECBCE08ED263143" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumValueOfSharesPerEmployee_EE38327BE8F96D1BC860CE08EE005B15" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_9F709A3C054021DE1D27CE08EE2DBBEA" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_AF0AE1F5C2A28C4DFECBCE08ED263143" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_9F709A3C054021DE1D27CE08EE2DBBEA" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StockIncentivePlansStockOptionPlansDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2B9EEF992AB661DB9CA0873AD573547B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2B9EEF992AB661DB9CA0873AD573547B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_12FE6F3A64343BAF2EA4873AD5730078" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2B9EEF992AB661DB9CA0873AD573547B" xlink:to="loc_us-gaap_PlanNameAxis_12FE6F3A64343BAF2EA4873AD5730078" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_80F7DFE8DFE61BE9CAF9873AD573789D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_12FE6F3A64343BAF2EA4873AD5730078" xlink:to="loc_us-gaap_PlanNameDomain_80F7DFE8DFE61BE9CAF9873AD573789D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_80F7DFE8DFE61BE9CAF9873AD573789D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_12FE6F3A64343BAF2EA4873AD5730078" xlink:to="loc_us-gaap_PlanNameDomain_80F7DFE8DFE61BE9CAF9873AD573789D" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockPlan2008Member" xlink:label="loc_vcyt_StockPlan2008Member_BACFC1418C5CD8F0ACD3873AD5743B4F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_80F7DFE8DFE61BE9CAF9873AD573789D" xlink:to="loc_vcyt_StockPlan2008Member_BACFC1418C5CD8F0ACD3873AD5743B4F" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockIncentivePlan2013Member" xlink:label="loc_vcyt_StockIncentivePlan2013Member_3C856DC0F8A2830CD85B873AD574D196" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_80F7DFE8DFE61BE9CAF9873AD573789D" xlink:to="loc_vcyt_StockIncentivePlan2013Member_3C856DC0F8A2830CD85B873AD574D196" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_F4FA7EC5A2746A8A3597873AD574138D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2B9EEF992AB661DB9CA0873AD573547B" xlink:to="loc_us-gaap_AwardTypeAxis_F4FA7EC5A2746A8A3597873AD574138D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92DFA629BDF8378493FB873AD5744A67_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_F4FA7EC5A2746A8A3597873AD574138D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92DFA629BDF8378493FB873AD5744A67_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92DFA629BDF8378493FB873AD5744A67" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_F4FA7EC5A2746A8A3597873AD574138D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92DFA629BDF8378493FB873AD5744A67" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_EmployeeAndNonEmployeeStockOptionMember" xlink:label="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_D70F718036E42176A756873AD5745DC4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92DFA629BDF8378493FB873AD5744A67" xlink:to="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_D70F718036E42176A756873AD5745DC4" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_IncentiveStockOptionsMember" xlink:label="loc_vcyt_IncentiveStockOptionsMember_F428EBA9BCC143BE6050873AD57422EC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_D70F718036E42176A756873AD5745DC4" xlink:to="loc_vcyt_IncentiveStockOptionsMember_F428EBA9BCC143BE6050873AD57422EC" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_NonStatutoryStockOptionsMember" xlink:label="loc_vcyt_NonStatutoryStockOptionsMember_4D7D95531AB825A5E15F873AD575BCFC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_D70F718036E42176A756873AD5745DC4" xlink:to="loc_vcyt_NonStatutoryStockOptionsMember_4D7D95531AB825A5E15F873AD575BCFC" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockIncentivePlan2013Member" xlink:label="loc_vcyt_StockIncentivePlan2013Member_7CCEF6DEDFC9E1529362873AD575E980" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_D70F718036E42176A756873AD5745DC4" xlink:to="loc_vcyt_StockIncentivePlan2013Member_7CCEF6DEDFC9E1529362873AD575E980" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TitleOfIndividualAxis" xlink:label="loc_us-gaap_TitleOfIndividualAxis_A86AFA04BF590B37B659873AD575E652" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2B9EEF992AB661DB9CA0873AD573547B" xlink:to="loc_us-gaap_TitleOfIndividualAxis_A86AFA04BF590B37B659873AD575E652" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_E6B539071A0BC0CA8C84873AD5754B05_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TitleOfIndividualAxis_A86AFA04BF590B37B659873AD575E652" xlink:to="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_E6B539071A0BC0CA8C84873AD5754B05_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_E6B539071A0BC0CA8C84873AD5754B05" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TitleOfIndividualAxis_A86AFA04BF590B37B659873AD575E652" xlink:to="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_E6B539071A0BC0CA8C84873AD5754B05" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_OutsideDirectorWhoWasNotPreviouslyEmployeeMember" xlink:label="loc_vcyt_OutsideDirectorWhoWasNotPreviouslyEmployeeMember_6D2D2F70CA13B82E2146873AD5750F22" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_E6B539071A0BC0CA8C84873AD5754B05" xlink:to="loc_vcyt_OutsideDirectorWhoWasNotPreviouslyEmployeeMember_6D2D2F70CA13B82E2146873AD5750F22" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_OutsideDirectorServingAsMemberOfBoardOfDirectorsForAtLeastSixMonthsMember" xlink:label="loc_vcyt_OutsideDirectorServingAsMemberOfBoardOfDirectorsForAtLeastSixMonthsMember_20B3CA898EA06D92AAB3873AD575F9A8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_E6B539071A0BC0CA8C84873AD5754B05" xlink:to="loc_vcyt_OutsideDirectorServingAsMemberOfBoardOfDirectorsForAtLeastSixMonthsMember_20B3CA898EA06D92AAB3873AD575F9A8" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_OutsideDirectorMember" xlink:label="loc_vcyt_OutsideDirectorMember_A5DB59DB0D6005292844873AD5759E32" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_E6B539071A0BC0CA8C84873AD5754B05" xlink:to="loc_vcyt_OutsideDirectorMember_A5DB59DB0D6005292844873AD5759E32" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_5D7B18197D43C670B56B873AD57505C4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2B9EEF992AB661DB9CA0873AD573547B" xlink:to="loc_us-gaap_RangeAxis_5D7B18197D43C670B56B873AD57505C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_6BFBB3527841B4C86EA7873AD575B35F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_5D7B18197D43C670B56B873AD57505C4" xlink:to="loc_us-gaap_RangeMember_6BFBB3527841B4C86EA7873AD575B35F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_6BFBB3527841B4C86EA7873AD575B35F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_5D7B18197D43C670B56B873AD57505C4" xlink:to="loc_us-gaap_RangeMember_6BFBB3527841B4C86EA7873AD575B35F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_1C30B0CDFC83167ECD21873AD575A986" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_6BFBB3527841B4C86EA7873AD575B35F" xlink:to="loc_us-gaap_MinimumMember_1C30B0CDFC83167ECD21873AD575A986" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_32311232233BEE2C5919873AD575F9C8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_6BFBB3527841B4C86EA7873AD575B35F" xlink:to="loc_us-gaap_MaximumMember_32311232233BEE2C5919873AD575F9C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_7F3D8A864DF3E5581FBE873AD5751242" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_7F3D8A864DF3E5581FBE873AD5751242" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfVotingPowerOfAllClassesOfStock" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfVotingPowerOfAllClassesOfStock_6D8BBBE08541C73FF06E873AD5766319" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfVotingPowerOfAllClassesOfStock_6D8BBBE08541C73FF06E873AD5766319" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermOfOptionsGrantedToEmployeesWhoOwnedSpecifiedPercentageOfClassOfStock" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermOfOptionsGrantedToEmployeesWhoOwnedSpecifiedPercentageOfClassOfStock_D33FB403A19374729511873AD5763DDC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermOfOptionsGrantedToEmployeesWhoOwnedSpecifiedPercentageOfClassOfStock_D33FB403A19374729511873AD5763DDC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_BE93F38C0836AAE89113873AD5765262" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_BE93F38C0836AAE89113873AD5765262" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfStockPercentageForGrantsToPersonsWhoOwnedSpecifiedPercentageOfClassOfStock" xlink:label="loc_vcyt_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfStockPercentageForGrantsToPersonsWhoOwnedSpecifiedPercentageOfClassOfStock_25A3D61E2051B26F9566873AD57695C3" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfStockPercentageForGrantsToPersonsWhoOwnedSpecifiedPercentageOfClassOfStock_25A3D61E2051B26F9566873AD57695C3" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentageYearOne" xlink:label="loc_vcyt_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentageYearOne_66DB6AEC86EFB0D7060A873AD57661B1" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentageYearOne_66DB6AEC86EFB0D7060A873AD57661B1" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CommonStockCapitalAdditionalSharesReservedForFutureIssuance" xlink:label="loc_vcyt_CommonStockCapitalAdditionalSharesReservedForFutureIssuance_0B7B15BB0667A4581464873AD576A04E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_CommonStockCapitalAdditionalSharesReservedForFutureIssuance_0B7B15BB0667A4581464873AD576A04E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_23AEDD993A22B8328F41873AD576668C" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_23AEDD993A22B8328F41873AD576668C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_5291C6C26FE21D87004C873AD576C4DF" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_5291C6C26FE21D87004C873AD576C4DF" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAnnualGrants" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAnnualGrants_E7F8451A955CB91081F9873AD5765815" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAnnualGrants_E7F8451A955CB91081F9873AD5765815" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsInitialGrants" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsInitialGrants_B1A6AFB119E49CE66ADA873AD5769B86" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsInitialGrants_B1A6AFB119E49CE66ADA873AD5769B86" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardPercentageVestingOnMonthlyBasis" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardPercentageVestingOnMonthlyBasis_FECA7F9A0B215DE3C304873AD576DD8F" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardPercentageVestingOnMonthlyBasis_FECA7F9A0B215DE3C304873AD576DD8F" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardPeriodOverWhichVestingWillBeOnMonthlyBasis" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardPeriodOverWhichVestingWillBeOnMonthlyBasis_0BED0D3286B4D3662F03873AD5765CC5" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardPeriodOverWhichVestingWillBeOnMonthlyBasis_0BED0D3286B4D3662F03873AD5765CC5" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPeriodForWhichDirectorHasToServeAsBoardOfDirectorToReceiveGrantToPurchaseShares" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPeriodForWhichDirectorHasToServeAsBoardOfDirectorToReceiveGrantToPurchaseShares_06EB03652229DA436990873AD5762464" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPeriodForWhichDirectorHasToServeAsBoardOfDirectorToReceiveGrantToPurchaseShares_06EB03652229DA436990873AD5762464" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardExpirationPeriodAfterTermination" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardExpirationPeriodAfterTermination_26C254F448344339504E873AD5769AD0" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8D4E28795FC622A16D6D873AD575A536" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardExpirationPeriodAfterTermination_26C254F448344339504E873AD5769AD0" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StockIncentivePlansTables" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_B3A7CE6C7ADB3FEFE461B7C47BF38D82" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0C0338CFF22F7AA5DFDFB7C47BF29D5B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_B3A7CE6C7ADB3FEFE461B7C47BF38D82" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0C0338CFF22F7AA5DFDFB7C47BF29D5B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_A2F03062F4972116BD9CB7C47BF2F192" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0C0338CFF22F7AA5DFDFB7C47BF29D5B" xlink:to="loc_us-gaap_AwardTypeAxis_A2F03062F4972116BD9CB7C47BF2F192" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ADADBCE39AC92CC7F69CB7C47BF318E5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_A2F03062F4972116BD9CB7C47BF2F192" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ADADBCE39AC92CC7F69CB7C47BF318E5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ADADBCE39AC92CC7F69CB7C47BF318E5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_A2F03062F4972116BD9CB7C47BF2F192" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ADADBCE39AC92CC7F69CB7C47BF318E5" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_EmployeeAndNonEmployeeStockOptionExcludingBonusCompensationMember" xlink:label="loc_vcyt_EmployeeAndNonEmployeeStockOptionExcludingBonusCompensationMember_23C51E61678750478707B7C47BF38891" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ADADBCE39AC92CC7F69CB7C47BF318E5" xlink:to="loc_vcyt_EmployeeAndNonEmployeeStockOptionExcludingBonusCompensationMember_23C51E61678750478707B7C47BF38891" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_EmployeeStockOptionExcludingBonusCompensationMember" xlink:label="loc_vcyt_EmployeeStockOptionExcludingBonusCompensationMember_C02C02BC4C183D3674E8B7C47BF32DF3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ADADBCE39AC92CC7F69CB7C47BF318E5" xlink:to="loc_vcyt_EmployeeStockOptionExcludingBonusCompensationMember_C02C02BC4C183D3674E8B7C47BF32DF3" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_NonEmployeeStockOptionMember" xlink:label="loc_vcyt_NonEmployeeStockOptionMember_0E57BDAB1D31385F8C31B7C47BF3A81B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ADADBCE39AC92CC7F69CB7C47BF318E5" xlink:to="loc_vcyt_NonEmployeeStockOptionMember_0E57BDAB1D31385F8C31B7C47BF3A81B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeStockMember" xlink:label="loc_us-gaap_EmployeeStockMember_67548C4DC4D0DC7F165AB7CDBD2F7075" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ADADBCE39AC92CC7F69CB7C47BF318E5" xlink:to="loc_us-gaap_EmployeeStockMember_67548C4DC4D0DC7F165AB7CDBD2F7075" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_E7A7F887D393A01C802AB7C47BF396E4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_B3A7CE6C7ADB3FEFE461B7C47BF38D82" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_E7A7F887D393A01C802AB7C47BF396E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_00A0695FAF94CA447B20B7C47BF36E0C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_B3A7CE6C7ADB3FEFE461B7C47BF38D82" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_00A0695FAF94CA447B20B7C47BF36E0C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock_26AC8A3F49B28A54C18DB7C47BF3010F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_B3A7CE6C7ADB3FEFE461B7C47BF38D82" xlink:to="loc_us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock_26AC8A3F49B28A54C18DB7C47BF3010F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StockholdersEquityDeficit" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StockholdersEquityDeficitTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/StockholdersEquityDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_142C826ECED415D4BCD06C7AFA3186A0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_54CBFA11F1F1649CDD636C7AFA305CFE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_142C826ECED415D4BCD06C7AFA3186A0" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_54CBFA11F1F1649CDD636C7AFA305CFE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_EC867524F4F19501E6926C7AFA30D6CD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_54CBFA11F1F1649CDD636C7AFA305CFE" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_EC867524F4F19501E6926C7AFA30D6CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_D5CCC10AAB886E68A5126C7AFA30F5A2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_EC867524F4F19501E6926C7AFA30D6CD" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_D5CCC10AAB886E68A5126C7AFA30F5A2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_D5CCC10AAB886E68A5126C7AFA30F5A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_EC867524F4F19501E6926C7AFA30D6CD" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_D5CCC10AAB886E68A5126C7AFA30F5A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_F89D7B25009F6B48F8DB6C7AFA30055F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_D5CCC10AAB886E68A5126C7AFA30F5A2" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_F89D7B25009F6B48F8DB6C7AFA30055F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_DB274245D9BFBE20916D6C7AFA30D8FE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_54CBFA11F1F1649CDD636C7AFA305CFE" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_DB274245D9BFBE20916D6C7AFA30D8FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_6B929CA3A0D335BBA8586C7AFA30648E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_DB274245D9BFBE20916D6C7AFA30D8FE" xlink:to="loc_us-gaap_EquityComponentDomain_6B929CA3A0D335BBA8586C7AFA30648E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_6B929CA3A0D335BBA8586C7AFA30648E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_DB274245D9BFBE20916D6C7AFA30D8FE" xlink:to="loc_us-gaap_EquityComponentDomain_6B929CA3A0D335BBA8586C7AFA30648E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_5C96C8A59B6C99285B196C7AFA30ED24" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_6B929CA3A0D335BBA8586C7AFA30648E" xlink:to="loc_us-gaap_CommonStockMember_5C96C8A59B6C99285B196C7AFA30ED24" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_8DD42BB30AF98DD376646C7AFA30E445" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_54CBFA11F1F1649CDD636C7AFA305CFE" xlink:to="loc_us-gaap_AwardTypeAxis_8DD42BB30AF98DD376646C7AFA30E445" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_519502F227DACA1155186C7AFA314900_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_8DD42BB30AF98DD376646C7AFA30E445" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_519502F227DACA1155186C7AFA314900_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_519502F227DACA1155186C7AFA314900" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_8DD42BB30AF98DD376646C7AFA30E445" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_519502F227DACA1155186C7AFA314900" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_EmployeeAndNonEmployeeStockOptionMember" xlink:label="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_029F81644693923EFF896C7AFA315256" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_519502F227DACA1155186C7AFA314900" xlink:to="loc_vcyt_EmployeeAndNonEmployeeStockOptionMember_029F81644693923EFF896C7AFA315256" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeStockMember" xlink:label="loc_us-gaap_EmployeeStockMember_EBB5F5A1338FF7803FEC6C7AFA319C60" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_519502F227DACA1155186C7AFA314900" xlink:to="loc_us-gaap_EmployeeStockMember_EBB5F5A1338FF7803FEC6C7AFA319C60" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_29F64A6DCD9A1C8161786C7AFA31423E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_54CBFA11F1F1649CDD636C7AFA305CFE" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_29F64A6DCD9A1C8161786C7AFA31423E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_7461C175845FC7DC3AD66C7AFA31962D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_29F64A6DCD9A1C8161786C7AFA31423E" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_7461C175845FC7DC3AD66C7AFA31962D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_7461C175845FC7DC3AD66C7AFA31962D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_29F64A6DCD9A1C8161786C7AFA31423E" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_7461C175845FC7DC3AD66C7AFA31962D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PrivatePlacementMember" xlink:label="loc_us-gaap_PrivatePlacementMember_221DF371DC00431288C06C7AFA3170FD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_7461C175845FC7DC3AD66C7AFA31962D" xlink:to="loc_us-gaap_PrivatePlacementMember_221DF371DC00431288C06C7AFA3170FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_D12CCC0D2A3EB580A8986C7AFA31A403" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_54CBFA11F1F1649CDD636C7AFA305CFE" xlink:to="loc_us-gaap_RangeAxis_D12CCC0D2A3EB580A8986C7AFA31A403" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_B9350DE956902021B93C6C7AFA31AB8C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_D12CCC0D2A3EB580A8986C7AFA31A403" xlink:to="loc_us-gaap_RangeMember_B9350DE956902021B93C6C7AFA31AB8C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_B9350DE956902021B93C6C7AFA31AB8C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_D12CCC0D2A3EB580A8986C7AFA31A403" xlink:to="loc_us-gaap_RangeMember_B9350DE956902021B93C6C7AFA31AB8C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_8E9DDFC0BA19B59FA5B16C7AFA312C02" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_B9350DE956902021B93C6C7AFA31AB8C" xlink:to="loc_us-gaap_MinimumMember_8E9DDFC0BA19B59FA5B16C7AFA312C02" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_CE236F79F5D8239F8F636C7AFA31504D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_B9350DE956902021B93C6C7AFA31AB8C" xlink:to="loc_us-gaap_MaximumMember_CE236F79F5D8239F8F636C7AFA31504D" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_CommonStockAbstract" xlink:label="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_142C826ECED415D4BCD06C7AFA3186A0" xlink:to="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_F6CB1F09EEEDE1BEC3946C7AFA31F450" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_F6CB1F09EEEDE1BEC3946C7AFA31F450" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_E6761140D8BB066453D76C7AFA3113FB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_E6761140D8BB066453D76C7AFA3113FB" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_VotingRightsForEachShareOfStock" xlink:label="loc_vcyt_VotingRightsForEachShareOfStock_44FEBF410A2428009EB86C7AFA3116CB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_vcyt_VotingRightsForEachShareOfStock_44FEBF410A2428009EB86C7AFA3116CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DividendsPayableCurrentAndNoncurrent" xlink:label="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_B1059579CA304A0922966C7AFA316A1D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_B1059579CA304A0922966C7AFA316A1D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_2ADC10B4CF8C5180F6D46C7AFA3187B8" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_2ADC10B4CF8C5180F6D46C7AFA3187B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_3C76EA5162300B91402B6C7AFA316E01" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_3C76EA5162300B91402B6C7AFA316E01" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_A57538186FABCD1B9F676C7AFA32DC02" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_A57538186FABCD1B9F676C7AFA32DC02" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:label="loc_us-gaap_CommonStockSharesIssued_3F84C041E583FE3D0CE96C7AFA32CA0D" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_CommonStockSharesIssued_3F84C041E583FE3D0CE96C7AFA32CA0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="loc_us-gaap_SharesIssuedPricePerShare_8366615CE3A6632B971B6C7AFA325F25" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_SharesIssuedPricePerShare_8366615CE3A6632B971B6C7AFA325F25" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_SaleofStockConsiderationReceivedonTransactionGross" xlink:label="loc_vcyt_SaleofStockConsiderationReceivedonTransactionGross_69C1D421D23E178C669D6C7AFA32679D" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_vcyt_SaleofStockConsiderationReceivedonTransactionGross_69C1D421D23E178C669D6C7AFA32679D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_5D8E6084750AFF9029226C7AFA32BC60" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_5D8E6084750AFF9029226C7AFA32BC60" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PaymentsOfStockIssuanceCosts" xlink:label="loc_us-gaap_PaymentsOfStockIssuanceCosts_F42F8D1CCAE030827E966C7AFA322A59" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_PaymentsOfStockIssuanceCosts_F42F8D1CCAE030827E966C7AFA322A59" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccountsReceivableGross" xlink:label="loc_us-gaap_AccountsReceivableGross_A162B5773B807934B5106C7AFA32BC39" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_AccountsReceivableGross_A162B5773B807934B5106C7AFA32BC39" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_A42C5F09FC827F02989E6C7AFA32BB28" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_A42C5F09FC827F02989E6C7AFA32BB28" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockIssuedAndSoldDuringPeriodSharesInPrivatePlacement" xlink:label="loc_vcyt_StockIssuedAndSoldDuringPeriodSharesInPrivatePlacement_D5206430522F20D7C06D6C7AFA325980" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_vcyt_StockIssuedAndSoldDuringPeriodSharesInPrivatePlacement_D5206430522F20D7C06D6C7AFA325980" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharePrice" xlink:label="loc_us-gaap_SharePrice_CD2E6254DCBD9752DBE86C7AFA32DEF0" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_SharePrice_CD2E6254DCBD9752DBE86C7AFA32DEF0" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ProceedsFromIssuanceOfPrivatePlacementGross" xlink:label="loc_vcyt_ProceedsFromIssuanceOfPrivatePlacementGross_8CCC664CCD48BA81D10D6C7AFA3298B6" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_vcyt_ProceedsFromIssuanceOfPrivatePlacementGross_8CCC664CCD48BA81D10D6C7AFA3298B6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProceedsFromIssuanceOfPrivatePlacement" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfPrivatePlacement_72D7D68FD1E8564C5EC26C7AFA325F31" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfPrivatePlacement_72D7D68FD1E8564C5EC26C7AFA325F31" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_PlacementAgentFeesAndOtherExpenses" xlink:label="loc_vcyt_PlacementAgentFeesAndOtherExpenses_B1AB458E34F2F4487E6F6C7AFA3213C5" xlink:type="locator" />
    <link:definitionArc order="19" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_CommonStockAbstract_D044749EE70013FEF5186C7AFA31C69D" xlink:to="loc_vcyt_PlacementAgentFeesAndOtherExpenses_B1AB458E34F2F4487E6F6C7AFA3213C5" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_EmployeeStockPurchasePlanAbstract" xlink:label="loc_vcyt_EmployeeStockPurchasePlanAbstract_156861831F99D91DF44F6C7AFA32D9DF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_142C826ECED415D4BCD06C7AFA3186A0" xlink:to="loc_vcyt_EmployeeStockPurchasePlanAbstract_156861831F99D91DF44F6C7AFA32D9DF" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriodMaximum" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriodMaximum_9138D5559901DB58DC956C7AFA321498" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_EmployeeStockPurchasePlanAbstract_156861831F99D91DF44F6C7AFA32D9DF" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriodMaximum_9138D5559901DB58DC956C7AFA321498" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_FA285DD080E4F283B74E6C7AFA32AAC4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_EmployeeStockPurchasePlanAbstract_156861831F99D91DF44F6C7AFA32D9DF" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_FA285DD080E4F283B74E6C7AFA32AAC4" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriod" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriod_97CA0044877275671D426C7AFA325EB9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_EmployeeStockPurchasePlanAbstract_156861831F99D91DF44F6C7AFA32D9DF" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriod_97CA0044877275671D426C7AFA325EB9" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumValueOfSharesPerEmployee" xlink:label="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumValueOfSharesPerEmployee_98FEB16DF54761CC70E66C7AFA326C58" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_EmployeeStockPurchasePlanAbstract_156861831F99D91DF44F6C7AFA32D9DF" xlink:to="loc_vcyt_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumValueOfSharesPerEmployee_98FEB16DF54761CC70E66C7AFA326C58" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_AA1D7B7D76133BE801796C7AFA324C27" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_142C826ECED415D4BCD06C7AFA3186A0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_AA1D7B7D76133BE801796C7AFA324C27" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_765C0DF5C063E54348946C7AFA325AD2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_AA1D7B7D76133BE801796C7AFA324C27" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_765C0DF5C063E54348946C7AFA325AD2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_23A0AB3F7E41C76F0DA66C7AFA332022" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_AA1D7B7D76133BE801796C7AFA324C27" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_23A0AB3F7E41C76F0DA66C7AFA332022" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_01BFA2A1FF91A1B34AD06C7AFA33B377" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_AA1D7B7D76133BE801796C7AFA324C27" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_01BFA2A1FF91A1B34AD06C7AFA33B377" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_1D5C1B19E918F97647626C7AFA33316E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_AA1D7B7D76133BE801796C7AFA324C27" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_1D5C1B19E918F97647626C7AFA33316E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_B8182382225A78ED874C6C7AFA330A63" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_AA1D7B7D76133BE801796C7AFA324C27" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_B8182382225A78ED874C6C7AFA330A63" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/SummaryOfSignificantAccountingPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/SummaryOfSignificantAccountingPoliciesCreditRiskRestrictedCashAndAllowanceForDoubtfulAccountsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskLineItems" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_3E7BE3DF44845DAA3A627533C81C8DE9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTable" xlink:label="loc_us-gaap_ConcentrationRiskTable_06E3DF851DDA201956D27533C816B899" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_3E7BE3DF44845DAA3A627533C81C8DE9" xlink:to="loc_us-gaap_ConcentrationRiskTable_06E3DF851DDA201956D27533C816B899" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_4E9EAEF4F9EEDB8418E97533C8161807" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_06E3DF851DDA201956D27533C816B899" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_4E9EAEF4F9EEDB8418E97533C8161807" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DB2847E28377DE174C967533C816B8E3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_4E9EAEF4F9EEDB8418E97533C8161807" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DB2847E28377DE174C967533C816B8E3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DB2847E28377DE174C967533C816B8E3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_4E9EAEF4F9EEDB8418E97533C8161807" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DB2847E28377DE174C967533C816B8E3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SalesRevenueNetMember" xlink:label="loc_us-gaap_SalesRevenueNetMember_0B1D7C4239D9DDF3C7BC7533C81633F7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DB2847E28377DE174C967533C816B8E3" xlink:to="loc_us-gaap_SalesRevenueNetMember_0B1D7C4239D9DDF3C7BC7533C81633F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccountsReceivableMember" xlink:label="loc_us-gaap_AccountsReceivableMember_B70B86E937163BFC65D57533C8168974" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DB2847E28377DE174C967533C816B8E3" xlink:to="loc_us-gaap_AccountsReceivableMember_B70B86E937163BFC65D57533C8168974" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_0B054044650092528EA57533C8169EBE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_06E3DF851DDA201956D27533C816B899" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_0B054044650092528EA57533C8169EBE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_86CF7BA918334D72D3757533C81BE390_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_0B054044650092528EA57533C8169EBE" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_86CF7BA918334D72D3757533C81BE390_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_86CF7BA918334D72D3757533C81BE390" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_0B054044650092528EA57533C8169EBE" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_86CF7BA918334D72D3757533C81BE390" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_3D66FE4AC1967D4B19977533C81B07A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_86CF7BA918334D72D3757533C81BE390" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_3D66FE4AC1967D4B19977533C81B07A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CreditConcentrationRiskMember" xlink:label="loc_us-gaap_CreditConcentrationRiskMember_9E96AC2FBB9F45D495267533C81BF274" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_86CF7BA918334D72D3757533C81BE390" xlink:to="loc_us-gaap_CreditConcentrationRiskMember_9E96AC2FBB9F45D495267533C81BF274" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_DEE34FA94EBE7C5659797533C81C8A3E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_06E3DF851DDA201956D27533C816B899" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_DEE34FA94EBE7C5659797533C81C8A3E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_9209D6DE93AEAE3679367533C81CA408_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_DEE34FA94EBE7C5659797533C81C8A3E" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_9209D6DE93AEAE3679367533C81CA408_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_9209D6DE93AEAE3679367533C81CA408" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_DEE34FA94EBE7C5659797533C81C8A3E" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_9209D6DE93AEAE3679367533C81CA408" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_HeadquartersAndLaboratoryFacilitiesSouthSanFranciscoMember" xlink:label="loc_vcyt_HeadquartersAndLaboratoryFacilitiesSouthSanFranciscoMember_F05DC095AA6FA9AD13D07533C81CF54C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_9209D6DE93AEAE3679367533C81CA408" xlink:to="loc_vcyt_HeadquartersAndLaboratoryFacilitiesSouthSanFranciscoMember_F05DC095AA6FA9AD13D07533C81CF54C" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_HeadquartersAndLaboratoryFacilitiesSouthSanFranciscoLeaseTwoMember" xlink:label="loc_vcyt_HeadquartersAndLaboratoryFacilitiesSouthSanFranciscoLeaseTwoMember_523DC338977FEDE797067533C81CBBC0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_9209D6DE93AEAE3679367533C81CA408" xlink:to="loc_vcyt_HeadquartersAndLaboratoryFacilitiesSouthSanFranciscoLeaseTwoMember_523DC338977FEDE797067533C81CBBC0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HealthCareOrganizationRevenueSourcesAxis" xlink:label="loc_us-gaap_HealthCareOrganizationRevenueSourcesAxis_7950100AFE64247BB8917533C81C5404" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_06E3DF851DDA201956D27533C816B899" xlink:to="loc_us-gaap_HealthCareOrganizationRevenueSourcesAxis_7950100AFE64247BB8917533C81C5404" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HealthCareOrganizationRevenueSourcesDomain" xlink:label="loc_us-gaap_HealthCareOrganizationRevenueSourcesDomain_BE5CB6C16D49848932BC7533C81CD1C7_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HealthCareOrganizationRevenueSourcesAxis_7950100AFE64247BB8917533C81C5404" xlink:to="loc_us-gaap_HealthCareOrganizationRevenueSourcesDomain_BE5CB6C16D49848932BC7533C81CD1C7_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HealthCareOrganizationRevenueSourcesDomain" xlink:label="loc_us-gaap_HealthCareOrganizationRevenueSourcesDomain_BE5CB6C16D49848932BC7533C81CD1C7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HealthCareOrganizationRevenueSourcesAxis_7950100AFE64247BB8917533C81C5404" xlink:to="loc_us-gaap_HealthCareOrganizationRevenueSourcesDomain_BE5CB6C16D49848932BC7533C81CD1C7" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_MedicareMember" xlink:label="loc_vcyt_MedicareMember_A0542D4CB2BDEBA8A7A27533C81C311D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HealthCareOrganizationRevenueSourcesDomain_BE5CB6C16D49848932BC7533C81CD1C7" xlink:to="loc_vcyt_MedicareMember_A0542D4CB2BDEBA8A7A27533C81C311D" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_UnitedHealthcareMember" xlink:label="loc_vcyt_UnitedHealthcareMember_44150666AA7F8A811B717533C81C49BF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HealthCareOrganizationRevenueSourcesDomain_BE5CB6C16D49848932BC7533C81CD1C7" xlink:to="loc_vcyt_UnitedHealthcareMember_44150666AA7F8A811B717533C81C49BF" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_AetnaMember" xlink:label="loc_vcyt_AetnaMember_557FFA8F32FD000FB2B97533C81CEDE8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HealthCareOrganizationRevenueSourcesDomain_BE5CB6C16D49848932BC7533C81CD1C7" xlink:to="loc_vcyt_AetnaMember_557FFA8F32FD000FB2B97533C81CEDE8" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ConcentrationRiskAbstract" xlink:label="loc_vcyt_ConcentrationRiskAbstract_12012544A8ED0DDA08937533C81C9993" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_3E7BE3DF44845DAA3A627533C81C8DE9" xlink:to="loc_vcyt_ConcentrationRiskAbstract_12012544A8ED0DDA08937533C81C9993" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_NumberOfMajorFinancialInstitutionsWithWhichCashAndCashEquivalentsDeposited" xlink:label="loc_vcyt_NumberOfMajorFinancialInstitutionsWithWhichCashAndCashEquivalentsDeposited_EC7E485E8AB3979635387533C81C52CC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ConcentrationRiskAbstract_12012544A8ED0DDA08937533C81C9993" xlink:to="loc_vcyt_NumberOfMajorFinancialInstitutionsWithWhichCashAndCashEquivalentsDeposited_EC7E485E8AB3979635387533C81C52CC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_BD27EE5D2226035697AD7533C81C58B1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_ConcentrationRiskAbstract_12012544A8ED0DDA08937533C81C9993" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_BD27EE5D2226035697AD7533C81C58B1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RestrictedCashAndInvestmentsAbstract" xlink:label="loc_us-gaap_RestrictedCashAndInvestmentsAbstract_4634EF3842DBBF4F72987533C81CD457" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_3E7BE3DF44845DAA3A627533C81C8DE9" xlink:to="loc_us-gaap_RestrictedCashAndInvestmentsAbstract_4634EF3842DBBF4F72987533C81CD457" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SecurityDeposit" xlink:label="loc_us-gaap_SecurityDeposit_D3D7A9B8932A5D483CB87533C81C35DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndInvestmentsAbstract_4634EF3842DBBF4F72987533C81CD457" xlink:to="loc_us-gaap_SecurityDeposit_D3D7A9B8932A5D483CB87533C81C35DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsNoncurrent" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_9C664BE87A07745A48DB7533C81C66C2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndInvestmentsAbstract_4634EF3842DBBF4F72987533C81CD457" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_9C664BE87A07745A48DB7533C81C66C2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/SummaryOfSignificantAccountingPoliciesIntangibleAssetsBonusAccrualsAndRevenueRecongitionDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_4C9AA5FFB2C84C89062E81C84580182F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_57301DF19B787C8F1D2581C84580A33D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_4C9AA5FFB2C84C89062E81C84580182F" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_57301DF19B787C8F1D2581C84580A33D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_16EC33714B1B67E2CED381C84580BCB7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_57301DF19B787C8F1D2581C84580A33D" xlink:to="loc_us-gaap_RangeAxis_16EC33714B1B67E2CED381C84580BCB7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_A57761E9925133B01F2981C84580D961_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_16EC33714B1B67E2CED381C84580BCB7" xlink:to="loc_us-gaap_RangeMember_A57761E9925133B01F2981C84580D961_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_A57761E9925133B01F2981C84580D961" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_16EC33714B1B67E2CED381C84580BCB7" xlink:to="loc_us-gaap_RangeMember_A57761E9925133B01F2981C84580D961" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_B1A1E06648A7C70A75DF81C845802BCC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_A57761E9925133B01F2981C84580D961" xlink:to="loc_us-gaap_MinimumMember_B1A1E06648A7C70A75DF81C845802BCC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_31B9DCE5EB5F08E34F2181C84580FE34" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_A57761E9925133B01F2981C84580D961" xlink:to="loc_us-gaap_MaximumMember_31B9DCE5EB5F08E34F2181C84580FE34" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_3AAE18994F9F201CE4EA81C8458072CD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_57301DF19B787C8F1D2581C84580A33D" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_3AAE18994F9F201CE4EA81C8458072CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_E90AFCA7D201952C528E81C84580EE9D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_3AAE18994F9F201CE4EA81C8458072CD" xlink:to="loc_us-gaap_ReceivableTypeDomain_E90AFCA7D201952C528E81C84580EE9D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_E90AFCA7D201952C528E81C84580EE9D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_3AAE18994F9F201CE4EA81C8458072CD" xlink:to="loc_us-gaap_ReceivableTypeDomain_E90AFCA7D201952C528E81C84580EE9D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccruedIncomeReceivableMember" xlink:label="loc_us-gaap_AccruedIncomeReceivableMember_81F425B69FDB6D0625AA81C84580FE23" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_E90AFCA7D201952C528E81C84580EE9D" xlink:to="loc_us-gaap_AccruedIncomeReceivableMember_81F425B69FDB6D0625AA81C84580FE23" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_1218F910C1C3447C89B781C84581E351" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_4C9AA5FFB2C84C89062E81C84580182F" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_1218F910C1C3447C89B781C84581E351" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RevenueRecognitionAbstract" xlink:label="loc_us-gaap_RevenueRecognitionAbstract_9A6B4B1AAC081F60C3D781C8458169DE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_4C9AA5FFB2C84C89062E81C84580182F" xlink:to="loc_us-gaap_RevenueRecognitionAbstract_9A6B4B1AAC081F60C3D781C8458169DE" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_RevenueRecognizedOnAccrualBasis" xlink:label="loc_vcyt_RevenueRecognizedOnAccrualBasis_44ABC90F545AE3B3539181C84581D207" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRecognitionAbstract_9A6B4B1AAC081F60C3D781C8458169DE" xlink:to="loc_vcyt_RevenueRecognizedOnAccrualBasis_44ABC90F545AE3B3539181C84581D207" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_RevenueRecognizedOnAccrualBasisPercentage" xlink:label="loc_vcyt_RevenueRecognizedOnAccrualBasisPercentage_06406259F6D49E05CF9881C845819B77" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRecognitionAbstract_9A6B4B1AAC081F60C3D781C8458169DE" xlink:to="loc_vcyt_RevenueRecognizedOnAccrualBasisPercentage_06406259F6D49E05CF9881C845819B77" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_RevenueRecognizedReceivedInCash" xlink:label="loc_vcyt_RevenueRecognizedReceivedInCash_46198CA004D866DA2C9281C84581A222" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRecognitionAbstract_9A6B4B1AAC081F60C3D781C8458169DE" xlink:to="loc_vcyt_RevenueRecognizedReceivedInCash_46198CA004D866DA2C9281C84581A222" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_RevenueRecognizedReceivedInCashPercentage" xlink:label="loc_vcyt_RevenueRecognizedReceivedInCashPercentage_18973AFB810BFB7D608481C84581D976" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRecognitionAbstract_9A6B4B1AAC081F60C3D781C8458169DE" xlink:to="loc_vcyt_RevenueRecognizedReceivedInCashPercentage_18973AFB810BFB7D608481C84581D976" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SalesRevenueNet" xlink:label="loc_us-gaap_SalesRevenueNet_E6CA0938F4329528B93681C845810806" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRecognitionAbstract_9A6B4B1AAC081F60C3D781C8458169DE" xlink:to="loc_us-gaap_SalesRevenueNet_E6CA0938F4329528B93681C845810806" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_RevenuePercent" xlink:label="loc_vcyt_RevenuePercent_958637A05968FFE8ABF981C84581D127" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRecognitionAbstract_9A6B4B1AAC081F60C3D781C8458169DE" xlink:to="loc_vcyt_RevenuePercent_958637A05968FFE8ABF981C84581D127" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDiluted_A8D30B7BCA5957429FF181C8458135DF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_4C9AA5FFB2C84C89062E81C84580182F" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDiluted_A8D30B7BCA5957429FF181C8458135DF" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/SummaryOfSignificantAccountingPoliciesLiquidityDetails" xlink:type="extended">
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_LiquidityLineItems" xlink:label="loc_vcyt_LiquidityLineItems_ED8687B53DBB495D9C143F81A4A632A7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_1A8FE8EF78AB7FA2925C3F81A4A5F61D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_vcyt_LiquidityLineItems_ED8687B53DBB495D9C143F81A4A632A7" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_1A8FE8EF78AB7FA2925C3F81A4A5F61D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_A3F6663DD9B81CF7A5F13F82414992E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1A8FE8EF78AB7FA2925C3F81A4A5F61D" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_A3F6663DD9B81CF7A5F13F82414992E0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_32E378EE8F10732F7E913F824209041D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_A3F6663DD9B81CF7A5F13F82414992E0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_32E378EE8F10732F7E913F824209041D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_32E378EE8F10732F7E913F824209041D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_A3F6663DD9B81CF7A5F13F82414992E0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_32E378EE8F10732F7E913F824209041D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_BD1DFD289839511AC3593F82424B28B7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_32E378EE8F10732F7E913F824209041D" xlink:to="loc_us-gaap_LineOfCreditMember_BD1DFD289839511AC3593F82424B28B7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_3DEC33016E2A24CB68423F8240F2938D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1A8FE8EF78AB7FA2925C3F81A4A5F61D" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_3DEC33016E2A24CB68423F8240F2938D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_50E3B9E7D150E4C698363F8241D553E6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_3DEC33016E2A24CB68423F8240F2938D" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_50E3B9E7D150E4C698363F8241D553E6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_50E3B9E7D150E4C698363F8241D553E6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_3DEC33016E2A24CB68423F8240F2938D" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_50E3B9E7D150E4C698363F8241D553E6" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_VisiumMember" xlink:label="loc_vcyt_VisiumMember_0388FFF1548E5EE1946C3F82443050B9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_50E3B9E7D150E4C698363F8241D553E6" xlink:to="loc_vcyt_VisiumMember_0388FFF1548E5EE1946C3F82443050B9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_BEA9C6A7BC475DD6EA3D3F8240B3C943" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1A8FE8EF78AB7FA2925C3F81A4A5F61D" xlink:to="loc_us-gaap_DebtInstrumentAxis_BEA9C6A7BC475DD6EA3D3F8240B3C943" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9D68C71ABC54283957453F82419973F4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_BEA9C6A7BC475DD6EA3D3F8240B3C943" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9D68C71ABC54283957453F82419973F4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9D68C71ABC54283957453F82419973F4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_BEA9C6A7BC475DD6EA3D3F8240B3C943" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9D68C71ABC54283957453F82419973F4" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_InitialTermLoanMember" xlink:label="loc_vcyt_InitialTermLoanMember_BFC4D122C0A8A35413FA3F82434111BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9D68C71ABC54283957453F82419973F4" xlink:to="loc_vcyt_InitialTermLoanMember_BFC4D122C0A8A35413FA3F82434111BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_83BE6065EB6731F63CC33F81A4A58EC0" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1A8FE8EF78AB7FA2925C3F81A4A5F61D" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_83BE6065EB6731F63CC33F81A4A58EC0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_D50C07721481BC8280713F81A4A5A97F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_83BE6065EB6731F63CC33F81A4A58EC0" xlink:to="loc_us-gaap_EquityComponentDomain_D50C07721481BC8280713F81A4A5A97F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_D50C07721481BC8280713F81A4A5A97F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_83BE6065EB6731F63CC33F81A4A58EC0" xlink:to="loc_us-gaap_EquityComponentDomain_D50C07721481BC8280713F81A4A5A97F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_5B3C378ADC88D26D5C093F81A4A68A1D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_D50C07721481BC8280713F81A4A5A97F" xlink:to="loc_us-gaap_CommonStockMember_5B3C378ADC88D26D5C093F81A4A68A1D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_A5A9A8323B938C1539E53F81A4A6D932" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1A8FE8EF78AB7FA2925C3F81A4A5F61D" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_A5A9A8323B938C1539E53F81A4A6D932" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_222C33ADEA6E6882D5D43F81A4A60EF9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_A5A9A8323B938C1539E53F81A4A6D932" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_222C33ADEA6E6882D5D43F81A4A60EF9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_222C33ADEA6E6882D5D43F81A4A60EF9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_A5A9A8323B938C1539E53F81A4A6D932" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_222C33ADEA6E6882D5D43F81A4A60EF9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PrivatePlacementMember" xlink:label="loc_us-gaap_PrivatePlacementMember_274BFC251AB851A04A7B3F81A4A6F01E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_222C33ADEA6E6882D5D43F81A4A60EF9" xlink:to="loc_us-gaap_PrivatePlacementMember_274BFC251AB851A04A7B3F81A4A6F01E" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_LiquidityAbstract" xlink:label="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityLineItems_ED8687B53DBB495D9C143F81A4A632A7" xlink:to="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_3EC9FFDC34DE4FE117D13F81A4A695D8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_3EC9FFDC34DE4FE117D13F81A4A695D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_7DBF9531991EF3F81DF33F81A4A65187" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_7DBF9531991EF3F81DF33F81A4A65187" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:label="loc_us-gaap_CommonStockSharesIssued_6743B12AD853079ABA573F81A4A6D6DF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_us-gaap_CommonStockSharesIssued_6743B12AD853079ABA573F81A4A6D6DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="loc_us-gaap_SharesIssuedPricePerShare_782F3162E4FFE56DECA43F81A4A660BF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_us-gaap_SharesIssuedPricePerShare_782F3162E4FFE56DECA43F81A4A660BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_FF37371CC0F65F6C6DC13F81A4A7EDEA" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_FF37371CC0F65F6C6DC13F81A4A7EDEA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PaymentsOfStockIssuanceCosts" xlink:label="loc_us-gaap_PaymentsOfStockIssuanceCosts_8FB4D05CAD57855AAF013F81A4A7F800" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_us-gaap_PaymentsOfStockIssuanceCosts_8FB4D05CAD57855AAF013F81A4A7F800" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_46E7873D945C61E16F353F82402C4947" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_46E7873D945C61E16F353F82402C4947" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_CCF4222C0672223A10783F82406D0B65" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_CCF4222C0672223A10783F82406D0B65" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_StockIssuedAndSoldDuringPeriodSharesInPrivatePlacement" xlink:label="loc_vcyt_StockIssuedAndSoldDuringPeriodSharesInPrivatePlacement_CA12C3E7F976D60068253F81A4A7AD0B" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_vcyt_StockIssuedAndSoldDuringPeriodSharesInPrivatePlacement_CA12C3E7F976D60068253F81A4A7AD0B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharePrice" xlink:label="loc_us-gaap_SharePrice_B040CFD463B56ACAEB043F81A4A763BA" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_us-gaap_SharePrice_B040CFD463B56ACAEB043F81A4A763BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProceedsFromIssuanceOfPrivatePlacement" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfPrivatePlacement_8D5010F1BFB85CE525653F81A4A7BA88" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfPrivatePlacement_8D5010F1BFB85CE525653F81A4A7BA88" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_PlacementAgentFeesAndOtherExpenses" xlink:label="loc_vcyt_PlacementAgentFeesAndOtherExpenses_2CD79503E15F2105EF9C3F81A4A77D2F" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_vcyt_LiquidityAbstract_76193A08DFF810BA21FD3F81A4A62465" xlink:to="loc_vcyt_PlacementAgentFeesAndOtherExpenses_2CD79503E15F2105EF9C3F81A4A77D2F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskLineItems" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_B3A3531AA8DEB900B14B81C8116EED37" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTable" xlink:label="loc_us-gaap_ConcentrationRiskTable_6137CB82D14EA1F112E581C8116DF885" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_B3A3531AA8DEB900B14B81C8116EED37" xlink:to="loc_us-gaap_ConcentrationRiskTable_6137CB82D14EA1F112E581C8116DF885" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_1CF3C62F7F7AC65F8E0581C8116E7F7F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_6137CB82D14EA1F112E581C8116DF885" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_1CF3C62F7F7AC65F8E0581C8116E7F7F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_34072A2E8AD9DF3CD06781C8116E791B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_1CF3C62F7F7AC65F8E0581C8116E7F7F" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_34072A2E8AD9DF3CD06781C8116E791B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_34072A2E8AD9DF3CD06781C8116E791B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_1CF3C62F7F7AC65F8E0581C8116E7F7F" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_34072A2E8AD9DF3CD06781C8116E791B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_BE42F11FEC3FFCA6DD3281C8116E0A2B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_34072A2E8AD9DF3CD06781C8116E791B" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_BE42F11FEC3FFCA6DD3281C8116E0A2B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CreditConcentrationRiskMember" xlink:label="loc_us-gaap_CreditConcentrationRiskMember_79A469C974F075B7CBB381C8116EFBC0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_34072A2E8AD9DF3CD06781C8116E791B" xlink:to="loc_us-gaap_CreditConcentrationRiskMember_79A469C974F075B7CBB381C8116EFBC0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_C9EB4D0830D23D216FB081C8116E7A29" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_6137CB82D14EA1F112E581C8116DF885" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_C9EB4D0830D23D216FB081C8116E7A29" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E8B6BEC0EBCF1EACB86B81C8116EA477_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_C9EB4D0830D23D216FB081C8116E7A29" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E8B6BEC0EBCF1EACB86B81C8116EA477_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E8B6BEC0EBCF1EACB86B81C8116EA477" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_C9EB4D0830D23D216FB081C8116E7A29" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E8B6BEC0EBCF1EACB86B81C8116EA477" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_SalesRevenueGrossMember" xlink:label="loc_vcyt_SalesRevenueGrossMember_2AC549F2DE2437E982C481C8116E139A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E8B6BEC0EBCF1EACB86B81C8116EA477" xlink:to="loc_vcyt_SalesRevenueGrossMember_2AC549F2DE2437E982C481C8116E139A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccountsReceivableMember" xlink:label="loc_us-gaap_AccountsReceivableMember_181539FB2210475AD1B781C8116EBFC5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E8B6BEC0EBCF1EACB86B81C8116EA477" xlink:to="loc_us-gaap_AccountsReceivableMember_181539FB2210475AD1B781C8116EBFC5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SchedulesOfConcentrationOfRiskByRiskFactorTextBlock" xlink:label="loc_us-gaap_SchedulesOfConcentrationOfRiskByRiskFactorTextBlock_64F5EE62BAF7DC4C777281C8116E1423" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_B3A3531AA8DEB900B14B81C8116EED37" xlink:to="loc_us-gaap_SchedulesOfConcentrationOfRiskByRiskFactorTextBlock_64F5EE62BAF7DC4C777281C8116E1423" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RevenueRecognitionAbstract" xlink:label="loc_us-gaap_RevenueRecognitionAbstract_D3F2432DBFAFE96DE7EA81C8116E8635" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_B3A3531AA8DEB900B14B81C8116EED37" xlink:to="loc_us-gaap_RevenueRecognitionAbstract_D3F2432DBFAFE96DE7EA81C8116E8635" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_ScheduleOfRevenueRecognitionCashAndAccrualBasisTableTextBlock" xlink:label="loc_vcyt_ScheduleOfRevenueRecognitionCashAndAccrualBasisTableTextBlock_97DCC9DD930CD429024B81C8116FD5F1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRecognitionAbstract_D3F2432DBFAFE96DE7EA81C8116E8635" xlink:to="loc_vcyt_ScheduleOfRevenueRecognitionCashAndAccrualBasisTableTextBlock_97DCC9DD930CD429024B81C8116FD5F1" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.veracyte.com/role/ThyroidCytopathologyPartners" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.veracyte.com/role/ThyroidCytopathologyPartnersDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_VariableInterestEntityLineItems" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_7A83991D030128C679D4888CE4B1AF7A" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_1A761302036A1DDD1503888CE4B187E1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_7A83991D030128C679D4888CE4B1AF7A" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_1A761302036A1DDD1503888CE4B187E1" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:label="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_64524F053E03DBC01F9A888CE4B188F7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_1A761302036A1DDD1503888CE4B187E1" xlink:to="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_64524F053E03DBC01F9A888CE4B188F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:label="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_D8664631FDF8BF7A8082888CE4B1A50A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_64524F053E03DBC01F9A888CE4B188F7" xlink:to="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_D8664631FDF8BF7A8082888CE4B1A50A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:label="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_D8664631FDF8BF7A8082888CE4B1A50A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_64524F053E03DBC01F9A888CE4B188F7" xlink:to="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_D8664631FDF8BF7A8082888CE4B1A50A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember" xlink:label="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_0BCE410CBC358038341B888CE4B1CEED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_D8664631FDF8BF7A8082888CE4B1A50A" xlink:to="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_0BCE410CBC358038341B888CE4B1CEED" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_AgreementTermsNonRenewalNoticePeriod" xlink:label="loc_vcyt_AgreementTermsNonRenewalNoticePeriod_05F4B8EA4D6BFECA1737888CE4B1B523" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_7A83991D030128C679D4888CE4B1AF7A" xlink:to="loc_vcyt_AgreementTermsNonRenewalNoticePeriod_05F4B8EA4D6BFECA1737888CE4B1B523" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_TestingAndEvaluationServicesExpense" xlink:label="loc_vcyt_TestingAndEvaluationServicesExpense_0C4C022E063FA4D6655F888CE4B113A4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_7A83991D030128C679D4888CE4B1AF7A" xlink:to="loc_vcyt_TestingAndEvaluationServicesExpense_0C4C022E063FA4D6655F888CE4B113A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="loc_us-gaap_AccountsPayableCurrent_0C6B42201D8E8A7F6EB7888CE4B10B50" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_7A83991D030128C679D4888CE4B1AF7A" xlink:to="loc_us-gaap_AccountsPayableCurrent_0C6B42201D8E8A7F6EB7888CE4B10B50" xlink:type="arc" />
    <link:loc xlink:href="vcyt-20161231.xsd#vcyt_OtherIncomeRentReimbursement" xlink:label="loc_vcyt_OtherIncomeRentReimbursement_54106210E441A63A1D41888CE4B10D8A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_7A83991D030128C679D4888CE4B1AF7A" xlink:to="loc_vcyt_OtherIncomeRentReimbursement_54106210E441A63A1D41888CE4B10D8A" xlink:type="arc" />
  </link:definitionLink>
</link:linkbase>
