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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 DbEkNcDEiDFdO4UBX7cvhicJqKtreh4ilfhIHfNGz+pyq2cmEQQD0fcbYsbSRMjP
 1xpR+fIXdYS9/evEXyD91w==

<SEC-DOCUMENT>0000018230-07-000421.txt : 20070814
<SEC-HEADER>0000018230-07-000421.hdr.sgml : 20070814
<ACCEPTANCE-DATETIME>20070814133622
ACCESSION NUMBER:		0000018230-07-000421
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031229
FILED AS OF DATE:		20070814
DATE AS OF CHANGE:		20070814

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CATERPILLAR INC
		CENTRAL INDEX KEY:			0000018230
		STANDARD INDUSTRIAL CLASSIFICATION:	CONSTRUCTION MACHINERY & EQUIP [3531]
		IRS NUMBER:				370602744
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		100 NE ADAMS ST
		CITY:			PEORIA
		STATE:			IL
		ZIP:			61629
		BUSINESS PHONE:		3096751000

	MAIL ADDRESS:	
		STREET 1:		100 NE ADAMS ST
		CITY:			PEORIA
		STATE:			IL
		ZIP:			61629

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	CATERPILLAR TRACTOR CO
		DATE OF NAME CHANGE:	19860623

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MAGOWAN PETER A
		CENTRAL INDEX KEY:			0001171799

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-00768
		FILM NUMBER:		071053334

	MAIL ADDRESS:	
		STREET 1:		100 NE ADAMS STREET
		CITY:			PEORIA
		STATE:			IL
		ZIP:			61629
</SEC-HEADER>
<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>2003-12-29</periodOfReport>

    <issuer>
        <issuerCik>0000018230</issuerCik>
        <issuerName>CATERPILLAR INC</issuerName>
        <issuerTradingSymbol>CAT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001171799</rptOwnerCik>
            <rptOwnerName>MAGOWAN PETER A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>PACIFIC BELL PARK</rptOwnerStreet1>
            <rptOwnerStreet2>24 WILLIE MAYS PLAZA</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94107</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common</value>
            </securityTitle>
            <transactionDate>
                <value>2003-12-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>120</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21342</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1400</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Reporting person disclaims beneficial ownership.</footnote>
        <footnote id="F2">Following this reported transaction, the reporting person held 21,342 shares.  As of the date this report is being filed, taking into account the stock split in July 2005, the reporting person now owns 266,681 shares.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Peter A. Magowan; L. J. Huxtable, POA</signatureName>
        <signatureDate>2007-08-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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