﻿<?xml version="1.0" encoding="utf-8"?>
<Return xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" returnVersion="2025v4.0" xmlns="http://www.irs.gov/efile">
  <ReturnHeader binaryAttachmentCnt="0">
    <ReturnTs>2026-08-15T00:10:35-04:00</ReturnTs>
    <TaxPeriodEndDt>2025-12-31</TaxPeriodEndDt>
    <ReturnTypeCd>990PF</ReturnTypeCd>
    <TaxPeriodBeginDt>2025-01-01</TaxPeriodBeginDt>
    <Filer>
      <EIN>460976803</EIN>
      <BusinessName>
        <BusinessNameLine1Txt>Center for Responsible Science</BusinessNameLine1Txt>
      </BusinessName>
      <BusinessNameControlTxt>CENT</BusinessNameControlTxt>
      <PhoneNum>8582097060</PhoneNum>
      <USAddress>
        <AddressLine1Txt>PO Box 508</AddressLine1Txt>
        <CityNm>Solana Beach</CityNm>
        <StateAbbreviationCd>CA</StateAbbreviationCd>
        <ZIPCd>92075</ZIPCd>
      </USAddress>
    </Filer>
    <BusinessOfficerGrp>
      <PersonNm>Robert P Isaacson</PersonNm>
      <PersonTitleTxt>President</PersonTitleTxt>
      <PhoneNum>8582097060</PhoneNum>
      <SignatureDt>2026-08-15</SignatureDt>
    </BusinessOfficerGrp>
    <TaxYr>2025</TaxYr>
    <BuildTS>2025-03-06 01:10:19Z</BuildTS>
  </ReturnHeader>
  <ReturnData documentCnt="1">
    <IRS990PF documentId="IRS990PF" softwareId="25023106" softwareVersionNum="V1.0" documentName="IRS990PF" referenceDocumentName="ReasonableCauseExplanation GeneralExplanationAttachment BinaryAttachment">
      <PF60MonthTermSect507b1BInd>X</PF60MonthTermSect507b1BInd>
      <Organization501c3ExemptPFInd>X</Organization501c3ExemptPFInd>
      <FMVAssetsEOYAmt>17714</FMVAssetsEOYAmt>
      <MethodOfAccountingCashInd>X</MethodOfAccountingCashInd>
      <AnalysisOfRevenueAndExpenses>
        <ContriRcvdRevAndExpnssAmt>3000</ContriRcvdRevAndExpnssAmt>
        <TotalRevAndExpnssAmt>3000</TotalRevAndExpnssAmt>
        <TotalNetInvstIncmAmt>0</TotalNetInvstIncmAmt>
        <TotalAdjNetIncmAmt>0</TotalAdjNetIncmAmt>
        <OtherExpensesRevAndExpnssAmt referenceDocumentName="AmortizationSchedule OtherExpensesSchedule">756</OtherExpensesRevAndExpnssAmt>
        <TotOprExpensesRevAndExpnssAmt>756</TotOprExpensesRevAndExpnssAmt>
        <TotOprExpensesNetInvstIncmAmt>0</TotOprExpensesNetInvstIncmAmt>
        <TotOprExpensesAdjNetIncmAmt>0</TotOprExpensesAdjNetIncmAmt>
        <TotOprExpensesDsbrsChrtblAmt>0</TotOprExpensesDsbrsChrtblAmt>
        <ContriPaidRevAndExpnssAmt>0</ContriPaidRevAndExpnssAmt>
        <ContriPaidDsbrsChrtblAmt>0</ContriPaidDsbrsChrtblAmt>
        <TotalExpensesRevAndExpnssAmt>756</TotalExpensesRevAndExpnssAmt>
        <TotalExpensesNetInvstIncmAmt>0</TotalExpensesNetInvstIncmAmt>
        <TotalExpensesAdjNetIncmAmt>0</TotalExpensesAdjNetIncmAmt>
        <TotalExpensesDsbrsChrtblAmt>0</TotalExpensesDsbrsChrtblAmt>
        <ExcessRevenueOverExpensesAmt>2244</ExcessRevenueOverExpensesAmt>
        <NetInvestmentIncomeAmt>0</NetInvestmentIncomeAmt>
        <AdjustedNetIncomeAmt>0</AdjustedNetIncomeAmt>
      </AnalysisOfRevenueAndExpenses>
      <Form990PFBalanceSheetsGrp>
        <CashBOYAmt>15470</CashBOYAmt>
        <CashEOYAmt>17714</CashEOYAmt>
        <CashEOYFMVAmt>17714</CashEOYFMVAmt>
        <TotalAssetsBOYAmt>15470</TotalAssetsBOYAmt>
        <TotalAssetsEOYAmt>17714</TotalAssetsEOYAmt>
        <TotalAssetsEOYFMVAmt>17714</TotalAssetsEOYFMVAmt>
        <TotalLiabilitiesBOYAmt>0</TotalLiabilitiesBOYAmt>
        <TotalLiabilitiesEOYAmt>0</TotalLiabilitiesEOYAmt>
        <OrgDoesNotFollowFASB117Ind>X</OrgDoesNotFollowFASB117Ind>
        <RetainedEarningBOYAmt>15470</RetainedEarningBOYAmt>
        <RetainedEarningEOYAmt>17714</RetainedEarningEOYAmt>
        <TotNetAstOrFundBalancesBOYAmt>15470</TotNetAstOrFundBalancesBOYAmt>
        <TotNetAstOrFundBalancesEOYAmt>17714</TotNetAstOrFundBalancesEOYAmt>
        <TotalLiabilitiesNetAstBOYAmt>15470</TotalLiabilitiesNetAstBOYAmt>
        <TotalLiabilitiesNetAstEOYAmt>17714</TotalLiabilitiesNetAstEOYAmt>
      </Form990PFBalanceSheetsGrp>
      <ChgInNetAssetsFundBalancesGrp>
        <TotNetAstOrFundBalancesBOYAmt>15470</TotNetAstOrFundBalancesBOYAmt>
        <ExcessRevenueOverExpensesAmt>2244</ExcessRevenueOverExpensesAmt>
        <SubtotalAmt>17714</SubtotalAmt>
        <TotNetAstOrFundBalancesEOYAmt>17714</TotNetAstOrFundBalancesEOYAmt>
      </ChgInNetAssetsFundBalancesGrp>
      <ExciseTaxBasedOnInvstIncmGrp>
        <InvestmentIncomeExciseTaxAmt>0</InvestmentIncomeExciseTaxAmt>
        <SubtotalAmt>0</SubtotalAmt>
        <TaxBasedOnInvestmentIncomeAmt>0</TaxBasedOnInvestmentIncomeAmt>
        <TotalPaymentsAndCreditsAmt>0</TotalPaymentsAndCreditsAmt>
        <TaxDueAmt>0</TaxDueAmt>
      </ExciseTaxBasedOnInvstIncmGrp>
      <StatementsRegardingActyGrp>
        <LegislativePoliticalActyInd referenceDocumentName="ExplanationOfLegisPoliticalActivities BinaryAttachment">false</LegislativePoliticalActyInd>
        <MoreThan100SpentInd>false</MoreThan100SpentInd>
        <Form1120POLFiledInd>false</Form1120POLFiledInd>
        <Section4955OrganizationTaxAmt>0</Section4955OrganizationTaxAmt>
        <Section4955ManagersTaxAmt>0</Section4955ManagersTaxAmt>
        <TaxReimbursedAmt>0</TaxReimbursedAmt>
        <ActivitiesNotPreviouslyRptInd referenceDocumentName="ActivitiesNotPreviouslyReportedExplanation">false</ActivitiesNotPreviouslyRptInd>
        <ChangesToArticlesOrBylawsInd referenceDocumentName="BinaryAttachment">false</ChangesToArticlesOrBylawsInd>
        <UnrelatedBusIncmOverLimitInd>false</UnrelatedBusIncmOverLimitInd>
        <OrganizationDissolvedEtcInd referenceDocumentName="DissolutionStatement LiquidationExplanationStatement BinaryAttachment">false</OrganizationDissolvedEtcInd>
        <Section508eRqrSatisfiedInd>true</Section508eRqrSatisfiedInd>
        <AtLeast5000InAssetsInd>true</AtLeast5000InAssetsInd>
        <OrgReportOrRegisterStateCd>CA</OrgReportOrRegisterStateCd>
        <Form990PFFiledWithAttyGenInd referenceDocumentName="ExplanationOfNonFilingWithAGStatement">true</Form990PFFiledWithAttyGenInd>
        <PrivateOperatingFoundationInd>true</PrivateOperatingFoundationInd>
        <NewSubstantialContributorsInd referenceDocumentName="SubstantialContributorsSchedule">false</NewSubstantialContributorsInd>
        <OwnControlledEntityInd referenceDocumentName="TransfersFromControlledEntitiesSchedule TransfersToControlledEntitiesSchedule">false</OwnControlledEntityInd>
        <DonorAdvisedFundInd referenceDocumentName="DonorAdvisedFundStatement">false</DonorAdvisedFundInd>
        <ComplyWithPublicInspRqrInd>true</ComplyWithPublicInspRqrInd>
        <WebsiteAddressTxt>crs-501.org</WebsiteAddressTxt>
        <PersonsWithBooksName>
          <BusinessNameLine1Txt>Robert Isaacson</BusinessNameLine1Txt>
        </PersonsWithBooksName>
        <PhoneNum>8582097060</PhoneNum>
        <LocationOfBooksUSAddress>
          <AddressLine1Txt>176 Solana Point Circle</AddressLine1Txt>
          <CityNm>Solana Beach</CityNm>
          <StateAbbreviationCd>CA</StateAbbreviationCd>
          <ZIPCd>92075</ZIPCd>
        </LocationOfBooksUSAddress>
        <ForeignAccountsQuestionInd>false</ForeignAccountsQuestionInd>
      </StatementsRegardingActyGrp>
      <StatementsRegardingActy4720Grp>
        <SaleOrExchDisqualifiedPrsnInd>false</SaleOrExchDisqualifiedPrsnInd>
        <BrrwOrLendDisqualifiedPrsnInd>false</BrrwOrLendDisqualifiedPrsnInd>
        <FurnGoodsDisqualifiedPrsnInd>false</FurnGoodsDisqualifiedPrsnInd>
        <PayCompDisqualifiedPrsnInd>false</PayCompDisqualifiedPrsnInd>
        <TransferAstDisqualifiedPrsnInd>false</TransferAstDisqualifiedPrsnInd>
        <PaymentToGovernmentOfficialInd>false</PaymentToGovernmentOfficialInd>
        <UncorrectedPriorActsInd>false</UncorrectedPriorActsInd>
        <UndistributedIncomePYInd>false</UndistributedIncomePYInd>
        <BusinessHoldingsInd>false</BusinessHoldingsInd>
        <JeopardyInvestmentsInd>false</JeopardyInvestmentsInd>
        <UncorrectedPYJeopardyInvstInd>false</UncorrectedPYJeopardyInvstInd>
        <InfluenceLegislationInd>false</InfluenceLegislationInd>
        <InfluenceElectionInd>false</InfluenceElectionInd>
        <GrantsToIndividualsInd>false</GrantsToIndividualsInd>
        <GrantsToOrganizationsInd>false</GrantsToOrganizationsInd>
        <NoncharitablePurposeInd>false</NoncharitablePurposeInd>
        <RcvFndsToPayPrsnlBnftCntrctInd>false</RcvFndsToPayPrsnlBnftCntrctInd>
        <PayPremiumsPrsnlBnftCntrctInd>false</PayPremiumsPrsnlBnftCntrctInd>
        <ProhibitedTaxShelterTransInd>false</ProhibitedTaxShelterTransInd>
        <SubjToTaxRmnrtnExPrchtPymtInd>false</SubjToTaxRmnrtnExPrchtPymtInd>
      </StatementsRegardingActy4720Grp>
      <OfficerDirTrstKeyEmplInfoGrp>
        <OfficerDirTrstKeyEmplGrp>
          <PersonNm referenceDocumentName="CompensationExplanation">Gerry Boss</PersonNm>
          <USAddress>
            <AddressLine1Txt>PO Box 508</AddressLine1Txt>
            <CityNm>Solana Beach</CityNm>
            <StateAbbreviationCd>CA</StateAbbreviationCd>
            <ZIPCd>92075</ZIPCd>
          </USAddress>
          <TitleTxt>Board Member</TitleTxt>
          <AverageHrsPerWkDevotedToPosRt>2</AverageHrsPerWkDevotedToPosRt>
          <CompensationAmt>0</CompensationAmt>
          <EmployeeBenefitProgramAmt>0</EmployeeBenefitProgramAmt>
          <ExpenseAccountOtherAllwncAmt>0</ExpenseAccountOtherAllwncAmt>
        </OfficerDirTrstKeyEmplGrp>
        <OfficerDirTrstKeyEmplGrp>
          <PersonNm referenceDocumentName="CompensationExplanation">Robert P Isaacson</PersonNm>
          <USAddress>
            <AddressLine1Txt>PO Box 508</AddressLine1Txt>
            <CityNm>Solana Beach</CityNm>
            <StateAbbreviationCd>CA</StateAbbreviationCd>
            <ZIPCd>92075</ZIPCd>
          </USAddress>
          <TitleTxt>President</TitleTxt>
          <AverageHrsPerWkDevotedToPosRt>8</AverageHrsPerWkDevotedToPosRt>
          <CompensationAmt>0</CompensationAmt>
          <EmployeeBenefitProgramAmt>0</EmployeeBenefitProgramAmt>
          <ExpenseAccountOtherAllwncAmt>0</ExpenseAccountOtherAllwncAmt>
        </OfficerDirTrstKeyEmplGrp>
        <OfficerDirTrstKeyEmplGrp>
          <PersonNm referenceDocumentName="CompensationExplanation">Kyle M Wesendorf</PersonNm>
          <USAddress>
            <AddressLine1Txt>PO Box 508</AddressLine1Txt>
            <CityNm>Solana Beach</CityNm>
            <StateAbbreviationCd>CA</StateAbbreviationCd>
            <ZIPCd>92075</ZIPCd>
          </USAddress>
          <TitleTxt>Secretary/Treasurer</TitleTxt>
          <AverageHrsPerWkDevotedToPosRt>3</AverageHrsPerWkDevotedToPosRt>
          <CompensationAmt>0</CompensationAmt>
          <EmployeeBenefitProgramAmt>0</EmployeeBenefitProgramAmt>
          <ExpenseAccountOtherAllwncAmt>0</ExpenseAccountOtherAllwncAmt>
        </OfficerDirTrstKeyEmplGrp>
        <CompOfHghstPdEmplOrNONETxt>NONE</CompOfHghstPdEmplOrNONETxt>
        <OtherEmployeePaidOver50kCnt>0</OtherEmployeePaidOver50kCnt>
        <CompOfHghstPdCntrctOrNONETxt>NONE</CompOfHghstPdCntrctOrNONETxt>
      </OfficerDirTrstKeyEmplInfoGrp>
      <SummaryOfDirectChrtblActyGrp>
        <Description1Txt>Continued educating the public about the use of animals in research.</Description1Txt>
        <Expenses1Amt>0</Expenses1Amt>
      </SummaryOfDirectChrtblActyGrp>
      <SumOfProgramRelatedInvstGrp>
        <Description1Txt>None</Description1Txt>
        <AllOtherProgramRltdInvstTotAmt referenceDocumentId="AllOtherProgramRelatedInvSch" referenceDocumentName="AllOtherProgramRelatedInvestmentsSchedule">0</AllOtherProgramRltdInvstTotAmt>
        <TotalAmt>0</TotalAmt>
      </SumOfProgramRelatedInvstGrp>
      <MinimumInvestmentReturnGrp>
        <AverageMonthlyFMVOfSecAmt>0</AverageMonthlyFMVOfSecAmt>
        <AverageMonthlyCashBalancesAmt>16592</AverageMonthlyCashBalancesAmt>
        <FMVAllOtherNoncharitableAstAmt>0</FMVAllOtherNoncharitableAstAmt>
        <TotalFMVOfUnusedAssetsAmt>16592</TotalFMVOfUnusedAssetsAmt>
        <AdjustedTotalFMVOfUnusedAstAmt>16592</AdjustedTotalFMVOfUnusedAstAmt>
        <CashDeemedCharitableAmt referenceDocumentName="CashDeemedCharitableExplanationStatement">249</CashDeemedCharitableAmt>
        <NetVlNoncharitableAssetsAmt>16343</NetVlNoncharitableAssetsAmt>
        <MinimumInvestmentReturnAmt>817</MinimumInvestmentReturnAmt>
      </MinimumInvestmentReturnGrp>
      <DistributableAmountGrp>
        <MinimumInvestmentReturnAmt>817</MinimumInvestmentReturnAmt>
        <TaxBasedOnInvestmentIncomeAmt>0</TaxBasedOnInvestmentIncomeAmt>
        <TotalTaxAmt>0</TotalTaxAmt>
        <DistributableBeforeAdjAmt>817</DistributableBeforeAdjAmt>
        <DistributableBeforeDedAmt>817</DistributableBeforeDedAmt>
        <DistributableAsAdjustedAmt>817</DistributableAsAdjustedAmt>
      </DistributableAmountGrp>
      <PFQualifyingDistributionsGrp>
        <ExpensesAndContributionsAmt referenceDocumentName="BorrowedFundsElection">0</ExpensesAndContributionsAmt>
        <ProgramRelatedInvstTotalAmt>0</ProgramRelatedInvstTotalAmt>
        <QualifyingDistributionsAmt>0</QualifyingDistributionsAmt>
      </PFQualifyingDistributionsGrp>
      <UndistributedIncomeGrp>
        <DistributableAsAdjustedAmt>817</DistributableAsAdjustedAmt>
        <PriorYear1Yr>2023</PriorYear1Yr>
        <PriorYear2Yr>2022</PriorYear2Yr>
        <PriorYear3Yr>2021</PriorYear3Yr>
        <TotalForPriorYearsAmt>71</TotalForPriorYearsAmt>
        <TotalExcessDistributionCyovAmt>0</TotalExcessDistributionCyovAmt>
        <QualifyingDistributionsAmt>0</QualifyingDistributionsAmt>
        <ExcessDistriCyovAppCYCorpusAmt>0</ExcessDistriCyovAppCYCorpusAmt>
        <ExcessDistributionCyovAppCYAmt>0</ExcessDistributionCyovAppCYAmt>
        <TotalCorpusAmt>0</TotalCorpusAmt>
        <PriorYearUndistributedIncmAmt>71</PriorYearUndistributedIncmAmt>
        <Taxable1Amt>71</Taxable1Amt>
        <Taxable2Amt>0</Taxable2Amt>
        <UndistributedIncomeCYAmt>817</UndistributedIncomeCYAmt>
        <ExcessDistriCyovToNextYrAmt>0</ExcessDistriCyovToNextYrAmt>
      </UndistributedIncomeGrp>
      <PrivateOperatingFoundationsGrp>
        <LessorAdjNetIncmMinInvstRetGrp>
          <CurrentYearAmt>0</CurrentYearAmt>
          <Year1Amt>0</Year1Amt>
          <TotalAmt>0</TotalAmt>
        </LessorAdjNetIncmMinInvstRetGrp>
        <Pct85LessorAdjIncmOrMinRetGrp>
          <CurrentYearAmt>0</CurrentYearAmt>
          <Year1Amt>0</Year1Amt>
          <Year2Amt>0</Year2Amt>
          <Year3Amt>0</Year3Amt>
          <TotalAmt>0</TotalAmt>
        </Pct85LessorAdjIncmOrMinRetGrp>
        <QualifyingDistributionsGrp>
          <CurrentYearAmt>0</CurrentYearAmt>
          <Year1Amt>1635</Year1Amt>
          <Year2Amt>615</Year2Amt>
          <Year3Amt>1000</Year3Amt>
          <TotalAmt>3250</TotalAmt>
        </QualifyingDistributionsGrp>
        <QualifyingDistriNotUsedDrtGrp>
          <TotalAmt>0</TotalAmt>
        </QualifyingDistriNotUsedDrtGrp>
        <QualifyingDistriMadeDrtGrp>
          <CurrentYearAmt>0</CurrentYearAmt>
          <Year1Amt>1635</Year1Amt>
          <Year2Amt>615</Year2Amt>
          <Year3Amt>1000</Year3Amt>
          <TotalAmt>3250</TotalAmt>
        </QualifyingDistriMadeDrtGrp>
        <TotalAssetsGrp>
          <TotalAmt>0</TotalAmt>
        </TotalAssetsGrp>
        <TotalAssetsSect4942j3BiGrp>
          <TotalAmt>0</TotalAmt>
        </TotalAssetsSect4942j3BiGrp>
        <TwoThirdsMinimumInvstRetGrp>
          <Year1Amt>70</Year1Amt>
          <Year2Amt>47</Year2Amt>
          <Year3Amt>49</Year3Amt>
          <TotalAmt>166</TotalAmt>
        </TwoThirdsMinimumInvstRetGrp>
        <TotalSupportGrp>
          <TotalAmt>0</TotalAmt>
        </TotalSupportGrp>
        <PublicSupportType>
          <TotalAmt>0</TotalAmt>
        </PublicSupportType>
        <LargestSupportFromEOGrp>
          <TotalAmt>0</TotalAmt>
        </LargestSupportFromEOGrp>
        <GrossInvestmentIncomeGrp>
          <TotalAmt>0</TotalAmt>
        </GrossInvestmentIncomeGrp>
      </PrivateOperatingFoundationsGrp>
      <SupplementaryInformationGrp>
        <OnlyContriToPreselectedInd>X</OnlyContriToPreselectedInd>
      </SupplementaryInformationGrp>
      <AnalysisIncomeProducingActyGrp>
        <SubtotalsIncmProducingActyGrp>
          <UnrelatedBusinessTaxblIncmAmt>0</UnrelatedBusinessTaxblIncmAmt>
          <ExclusionAmt>0</ExclusionAmt>
          <RelatedOrExemptFunctionIncmAmt>0</RelatedOrExemptFunctionIncmAmt>
        </SubtotalsIncmProducingActyGrp>
        <TotalIncomeProducingActyAmt>0</TotalIncomeProducingActyAmt>
      </AnalysisIncomeProducingActyGrp>
      <TrnsfrTransRlnNonchrtblEOGrp>
        <TrnsfrOfCashToNonchrtblEOInd>false</TrnsfrOfCashToNonchrtblEOInd>
        <TrnsfrOtherAssetNonchrtblEOInd>false</TrnsfrOtherAssetNonchrtblEOInd>
        <SalesOrExchangesOfAssetsInd>false</SalesOrExchangesOfAssetsInd>
        <PurchaseOfAssetsNonchrtblEOInd>false</PurchaseOfAssetsNonchrtblEOInd>
        <RentalOfFacilitiesOthAssetsInd>false</RentalOfFacilitiesOthAssetsInd>
        <ReimbursementArrangementsInd>false</ReimbursementArrangementsInd>
        <LoansOrLoanGuaranteesInd>false</LoansOrLoanGuaranteesInd>
        <PerformanceOfServicesEtcInd>false</PerformanceOfServicesEtcInd>
        <SharingOfFacilitiesEtcInd>false</SharingOfFacilitiesEtcInd>
        <RelationshipsNonchrtblEOInd>false</RelationshipsNonchrtblEOInd>
      </TrnsfrTransRlnNonchrtblEOGrp>
    </IRS990PF>
  </ReturnData>
</Return>