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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 HYqnN6xLs9JW5kf7x0yljVA79Gxu/hiIQsgwVilpsX6uedkp0sdPXZ2sgmOzf8qy
 8qq3U329tNyO6Zjbk6O+fw==

<SEC-DOCUMENT>0001036032-03-000007.txt : 20031231
<SEC-HEADER>0001036032-03-000007.hdr.sgml : 20031231
<ACCEPTANCE-DATETIME>20031231192530
ACCESSION NUMBER:		0001036032-03-000007
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031231
FILED AS OF DATE:		20031231

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			GATX CORP
		CENTRAL INDEX KEY:			0000040211
		STANDARD INDUSTRIAL CLASSIFICATION:	TRANSPORTATION SERVICES [4700]
		IRS NUMBER:				361124040
		STATE OF INCORPORATION:			NY
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		500 W MONROE  ST
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60661
		BUSINESS PHONE:		3126216200

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	GENERAL AMERICAN TRANSPORTATION CORP
		DATE OF NAME CHANGE:	19750722

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			DUDDY GAIL L
		CENTRAL INDEX KEY:			0001036032

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-02328
		FILM NUMBER:		031081066

	BUSINESS ADDRESS:	
		STREET 1:		C/O GATX CORPORATION
		STREET 2:		500 W MONROE
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60661
		BUSINESS PHONE:		3126216603

	MAIL ADDRESS:	
		STREET 1:		C/O GATX CORPORTATION
		STREET 2:		500 W MONROE
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60661
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
    <periodOfReport>2003-12-31</periodOfReport>
    <notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000040211</issuerCik>
        <issuerName>GATX CORP</issuerName>
        <issuerTradingSymbol>GMT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001036032</rptOwnerCik>
            <rptOwnerName>DUDDY GAIL L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>GATX CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>500 WEST MONROE STREET</rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60661</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President Human Resources</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>
  <nonDerivativeTable>
    <nonDerivativeHolding>
      <securityTitle>
          <value>Common Stock</value>
      </securityTitle>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>8702.27</value>
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>D</value>
          </directOrIndirectOwnership>
      </ownershipNature>
   </nonDerivativeHolding>
    <nonDerivativeHolding>
      <securityTitle>
          <value>Common Stock - 401(k)</value>
      </securityTitle>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>7165.52</value>
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>I</value>
          </directOrIndirectOwnership>
          <natureOfOwnership>
              <value>401(k) Plan</value>
          </natureOfOwnership>
      </ownershipNature>
   </nonDerivativeHolding>
  </nonDerivativeTable>
  <derivativeTable>
   <derivativeTransaction>
      <securityTitle>
          <value>2002 Phantom Restricted Stock </value>
              <footnoteId id="F1" />
      </securityTitle>
      <conversionOrExercisePrice>
              <footnoteId id="F2" />
      </conversionOrExercisePrice>
      <transactionDate>
          <value>2003-12-31</value>
      </transactionDate>
      <transactionCoding>
          <transactionFormType>4</transactionFormType>
          <transactionCode>D</transactionCode>
          <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionAmounts>
          <transactionShares>
              <value>2000.00</value>
          </transactionShares>
          <transactionPricePerShare>
              <value>0</value>
          </transactionPricePerShare>
          <transactionAcquiredDisposedCode>
              <value>D</value>
          </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <exerciseDate>
              <footnoteId id="F3" />
      </exerciseDate>
      <expirationDate>
              <footnoteId id="F3" />
      </expirationDate>
      <underlyingSecurity>
          <underlyingSecurityTitle>
              <value>Common Stock</value>
          </underlyingSecurityTitle>
          <underlyingSecurityShares>
              <value>2000.00</value>
          </underlyingSecurityShares>
      </underlyingSecurity>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>0.00</value>
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>D</value>
          </directOrIndirectOwnership>
      </ownershipNature>
   </derivativeTransaction>
  </derivativeTable>
<footnotes>
   <footnote id="F1">Settlement of previously granted phantom restricted stock payable only in cash.</footnote>
   <footnote id="F2">1-for-1</footnote>
   <footnote id="F3">One third of the grant vested and became payable on December 31 2002, the remaining two thirds of the grant vested and became pay
able on December 31, 2003.</footnote>
</footnotes>
<remarks></remarks>    <ownerSignature>
       <signatureName>Lisa M. Ibarra, by Power of Attorney on behelf of Gail L. Du</signatureName>
       <signatureDate>2003-12-31</signatureDate>
    </ownerSignature>
</ownershipDocument>

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