-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0000919574-09-005212.txt : 20090313
<SEC-HEADER>0000919574-09-005212.hdr.sgml : 20090313
<ACCEPTANCE-DATETIME>20090312201241
ACCESSION NUMBER:		0000919574-09-005212
CONFORMED SUBMISSION TYPE:	D/A
PUBLIC DOCUMENT COUNT:		1
ITEM INFORMATION:		Rule 506
ITEM INFORMATION:		Investment Company Act Section 3(c)
ITEM INFORMATION:		Section 3(c)(7)
FILED AS OF DATE:		20090313
DATE AS OF CHANGE:		20090312
EFFECTIVENESS DATE:		20090313

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			AQR ABSOLUTE RETURN INSTITUTIONAL FUND LP
		CENTRAL INDEX KEY:			0001069070
		IRS NUMBER:				000000000

	FILING VALUES:
		FORM TYPE:		D/A
		SEC ACT:		1933 Act
		SEC FILE NUMBER:	021-47364
		FILM NUMBER:		09677130

	BUSINESS ADDRESS:	
		STREET 1:		1O ROCKEFELLER PLAZA
		STREET 2:		SUITE 624
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10020
		BUSINESS PHONE:		2122184400
</SEC-HEADER>
<DOCUMENT>
<TYPE>D/A
<SEQUENCE>1
<FILENAME>primary_doc.xml
<TEXT>
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    <submissionType>D/A</submissionType>

    <testOrLive>LIVE</testOrLive>

    <primaryIssuer>
        <cik>0001069070</cik>
        <entityName>AQR ABSOLUTE RETURN INSTITUTIONAL FUND LP</entityName>
        <issuerAddress>
            <street1>Two Greenwich Plaza, 3rd Floor</street1>
            <city>Greenwich</city>
            <stateOrCountry>CT</stateOrCountry>
            <zipCode>06830</zipCode>
        </issuerAddress>
        <issuerPhoneNumber>2037423700</issuerPhoneNumber>
        <issuerPreviousNameList>
            <value>None</value>
        </issuerPreviousNameList>
        <jurisdictionOfInc></jurisdictionOfInc>
        <entityType>Limited Partnership</entityType>
        <yearOfInc>
            <overFiveYears>true</overFiveYears>
        </yearOfInc>
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    <relatedPersonsList>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Gregor</firstName>
                <middleName>M</middleName>
                <lastName>Andrade</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Gregor Andrade is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Bradley</firstName>
                <middleName>D</middleName>
                <lastName>Asness</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Bradley Asness is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Clifford</firstName>
                <middleName>S</middleName>
                <lastName>Asness</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Clifford Asness is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Abdon</firstName>
                <middleName></middleName>
                <lastName>Bolivar</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Abdon Bolivar is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Jacques</firstName>
                <middleName>A</middleName>
                <lastName>Friedman</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Jacques Friedman is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>John</firstName>
                <middleName></middleName>
                <lastName>Howard</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>John Howard is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Brian</firstName>
                <middleName>K</middleName>
                <lastName>Hurst</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Brian Hurst is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Ronen</firstName>
                <middleName></middleName>
                <lastName>Israel</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Ronen Israel is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>David</firstName>
                <middleName>G</middleName>
                <lastName>Kabiller</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>David Kabiller is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Robert</firstName>
                <middleName>J.</middleName>
                <lastName>Krail</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Robert Krail is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Oktay</firstName>
                <middleName></middleName>
                <lastName>Kurbanov</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Oktay Kurbanov is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>John</firstName>
                <middleName>M</middleName>
                <lastName>Liew</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>John Liew is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Stephen</firstName>
                <middleName>J.</middleName>
                <lastName>Mellas</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Stephen Mellas is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Michael</firstName>
                <middleName>A</middleName>
                <lastName>Mendelson</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Michael Mendelson is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Lars</firstName>
                <middleName>N</middleName>
                <lastName>Nielson</lastName>
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            <relatedPersonAddress>
                <street1>c/o AQR Capital Management, LLC</street1>
                <street2>Two Greenwich Plaza, 3rd Floor</street2>
                <city>Greenwich</city>
                <stateOrCountry>CT</stateOrCountry>
                <zipCode>06830</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Lars Nielson is an executive officer of AQR Capital Management II, LLC, the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
    </relatedPersonsList>

    <offeringData>
        <industryGroup>
            <industryGroupType>Pooled Investment Fund</industryGroupType>
            <investmentFundInfo>
                <investmentFundType>Hedge Fund</investmentFundType>
                <is40Act>false</is40Act>
            </investmentFundInfo>
        </industryGroup>
        <issuerSize>
            <aggregateNetAssetValueRange>Decline to Disclose</aggregateNetAssetValueRange>
        </issuerSize>
        <federalExemptionsExclusions>
            <item>06</item>
            <item>3C</item>
            <item>3C.7</item>
        </federalExemptionsExclusions>
        <typeOfFiling>
            <newOrAmendment>
                <isAmendment>true</isAmendment>
                <previousAccessionNumber>9999999997-07-016496</previousAccessionNumber>
            </newOrAmendment>
            <dateOfFirstSale>
                <value>1998-08-01</value>
            </dateOfFirstSale>
        </typeOfFiling>
        <durationOfOffering>
            <moreThanOneYear>true</moreThanOneYear>
        </durationOfOffering>
        <typesOfSecuritiesOffered>
            <isPooledInvestmentFundType>true</isPooledInvestmentFundType>
        </typesOfSecuritiesOffered>
        <businessCombinationTransaction>
            <isBusinessCombinationTransaction>false</isBusinessCombinationTransaction>
        </businessCombinationTransaction>
        <minimumInvestmentAccepted>5000000</minimumInvestmentAccepted>
        <salesCompensationList></salesCompensationList>
        <offeringSalesAmounts>
            <totalOfferingAmount>Indefinite</totalOfferingAmount>
            <totalAmountSold>1305381296</totalAmountSold>
            <totalRemaining>Indefinite</totalRemaining>
        </offeringSalesAmounts>
        <investors>
            <hasNonAccreditedInvestors>false</hasNonAccreditedInvestors>
            <totalNumberAlreadyInvested>187</totalNumberAlreadyInvested>
        </investors>
        <salesCommissionsFindersFees>
            <salesCommissions>
                <dollarAmount>0</dollarAmount>
            </salesCommissions>
            <findersFees>
                <dollarAmount>0</dollarAmount>
            </findersFees>
        </salesCommissionsFindersFees>
        <useOfProceeds>
            <grossProceedsUsed>
                <dollarAmount>0</dollarAmount>
                <isEstimate>true</isEstimate>
            </grossProceedsUsed>
            <clarificationOfResponse>The General Partner (or its affiliate) is entitled to receive an annual management fee in an amount equal to a specified percentage of assets under management.</clarificationOfResponse>
        </useOfProceeds>
        <signatureBlock>
            <authorizedRepresentative>true</authorizedRepresentative>
            <signature>
                <issuerName>AQR Absolute Return Institutional Fund, L.P.</issuerName>
                <signatureName>/s/ Bradley D. Asness</signatureName>
                <nameOfSigner>Bradley D. Asness</nameOfSigner>
                <signatureTitle>Authorized Signatory</signatureTitle>
                <signatureDate>2009-03-10</signatureDate>
            </signature>
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-----END PRIVACY-ENHANCED MESSAGE-----