<SUBMISSION>
<ACCESSION-NUMBER>0001279304-04-000026
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20040702
<FILING-DATE>20040707
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>KILROY JOHN B JR
<CIK>0001214277
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-12675
<FILM-NUMBER>04904224
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>12200 W OLYMPIC BLVD
<STREET2>SUITE 200
<CITY>LOS ANGELES
<STATE>CA
<ZIP>90064
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>KILROY REALTY CORP
<CIK>0001025996
<ASSIGNED-SIC>6798
<IRS-NUMBER>954598246
<STATE-OF-INCORPORATION>MD
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>2250 E IMPERIAL HWY
<STREET2>C/O KILROY INDUSTRIES
<CITY>EL SEGUNDO
<STATE>CA
<ZIP>90245
<PHONE>3105635500
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>C/O KILROY INDUSTRIES
<STREET2>2250 E IMPERIAL HIGHWAY #1200
<CITY>EL SEGUNDO
<STATE>CA
<ZIP>90245
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-07-02</periodOfReport>

    <issuer>
        <issuerCik>0001025996</issuerCik>
        <issuerName>KILROY REALTY CORP</issuerName>
        <issuerTradingSymbol>KRC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001214277</rptOwnerCik>
            <rptOwnerName>KILROY JOHN B JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>12200 WEST OLYMPIC BLVD.</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90064</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2004-07-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>220457</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2004-07-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>34.4528</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>200457</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>364200</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Kilroy Industries</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Common Limited Partnership Units of Kilroy Realty, L.P.</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-07-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>27.756</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>1999-04-30</value>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>854937</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeHolding>
            <securityTitle>
                <value>Common Limited Partnership Units of Kilroy Realty, L.P.</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>605533</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>605533</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>N/A</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">20,000 shares of Kilroy Realty Corporation Common Stock were issued in exchange for 20,000 Common Limited Partnership Units of Kilroy Realty, L.P., a Deleware limited partnership.  The exchanged Common Limited Partnership Units of Kilroy Realty, L.P., were originally issued in exchange for the contribution of real property and related assets to Kilroy Realty, L.P.</footnote>
        <footnote id="F2">John B. Kilroy, Jr. disclaims beneficial ownership except to the extent of his respective interest in Kilroy Industries.</footnote>
        <footnote id="F3">There is no expiration date related to the conversion of Common Limited Partership Units of Kilroy Realty, L.P. to shares of Kilroy Realty Corporation Common Stock.</footnote>
        <footnote id="F4">604,400 Common Limited Partnership Units were eligible to be converted into shares of Kilroy Realty Corporation Common Stock on January 31, 1999 and 1,133 Common Limited Partnership Units were eligible to be converted into shares of Kilroy Realty Corporation Common Stock on October 6, 2001.</footnote>
        <footnote id="F5">Includes (a) 600,052 Common Limited Partnership Units owned by Kilroy Industries (for which John B. Kilroy, Jr. disclaims beneficial interest except to the extent of his respective interest in Kilroy Industries), (b) 4,348 Common Limited Partnership Units owned by Kilroy Technologies LLC (for which John B. Kilroy, Jr. disclaims beneficial interest except to the extent of his respective interest in Kilroy Technologies LLC), and (c) 1,133 Common Limited Partnership Units owned by KAICO (for which John B. Kilroy, Jr. disclaims beneficial interest except to the extent of his respective interest in KAICO)</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Tyler H. Rose, as attorney-in-fact for John B. Kilroy, Jr.</signatureName>
        <signatureDate>2004-07-07</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
