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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 FnubVgVewkoauGQUe6Gamw==

<SEC-DOCUMENT>0000716039-04-000070.txt : 20040406
<SEC-HEADER>0000716039-04-000070.hdr.sgml : 20040406
<ACCEPTANCE-DATETIME>20040406203305
ACCESSION NUMBER:		0000716039-04-000070
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040331
FILED AS OF DATE:		20040406

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CREIGHTON JOHN W JR
		CENTRAL INDEX KEY:			0001180164

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-08483
		FILM NUMBER:		04721268

	BUSINESS ADDRESS:	
		STREET 1:		C/O UAL CORP
		STREET 2:		P O BOX 66919
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60666
		BUSINESS PHONE:		8477004000

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			UNOCAL CORP
		CENTRAL INDEX KEY:			0000716039
		STANDARD INDUSTRIAL CLASSIFICATION:	CRUDE PETROLEUM & NATURAL GAS [1311]
		IRS NUMBER:				953825062
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2141 ROSECRANS AVE
		STREET 2:		STE 4000
		CITY:			EL SEGUNDO
		STATE:			CA
		ZIP:			90245
		BUSINESS PHONE:		3107267600

	MAIL ADDRESS:	
		STREET 1:		2141 ROSECRANS AVE
		STREET 2:		STE 4000
		CITY:			EL SEGUNDO
		STATE:			CA
		ZIP:			90245
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>f4aforcrei.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2004-03-31</periodOfReport>

    <dateOfOriginalSubmission>2004-04-02</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000716039</issuerCik>
        <issuerName>UNOCAL CORP</issuerName>
        <issuerTradingSymbol>UCL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001180164</rptOwnerCik>
            <rptOwnerName>CREIGHTON JOHN W JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>MADRONA VENTURE GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>1000 SECOND AVENUE, SUITE 3700</rptOwnerStreet2>
            <rptOwnerCity>SEATTLE</rptOwnerCity>
            <rptOwnerState>WA</rptOwnerState>
            <rptOwnerZipCode>98104</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock $1.00 Par Value</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2004-03-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>185.3666</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>37.4952</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>38329.348</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Common Stock has attached Preferred Stock Purchase Rights.
If and when the Rights become exercisable, the holders
would initially be entitled to purchase one one-hundredth
of a share of Series B Junior Participating Preferred stock
at a purchase price determined pursuant to the Rights
Agreement.</footnote>
        <footnote id="F2">Units credited for dividend equivalent on deferred
compensation under the 2001 Directors' Deferred
Compensation and Stock Award Plan.  Each unit is payable in
one share of Common Stock at the end of the deferral
periods.  This amendment is filed because the Form 4 filed
on April 2, 2004 did not include these units.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Paul R. Moore, Attorney-In-Fact</signatureName>
        <signatureDate>2004-04-06</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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