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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,
 D6p8fnjMQWgR1fc7w3A/Uaj81enjjitXf/ibaGN01HJB7pHqykcqkhsBziYpMHCf
 0Dvja03wIAyQDEJTEx13VQ==

<SEC-DOCUMENT>0001243739-03-000012.txt : 20030804
<SEC-HEADER>0001243739-03-000012.hdr.sgml : 20030804
<ACCEPTANCE-DATETIME>20030804144643
ACCESSION NUMBER:		0001243739-03-000012
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030731
FILED AS OF DATE:		20030804

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BERUBE BRIAN A
		CENTRAL INDEX KEY:			0001243739

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-05667
		FILM NUMBER:		03820281

	BUSINESS ADDRESS:	
		STREET 1:		C/O CABOT CORPORATION
		STREET 2:		TWO SEAPORT LANE
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02210
		BUSINESS PHONE:		6173450100

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CABOT CORP
		CENTRAL INDEX KEY:			0000016040
		STANDARD INDUSTRIAL CLASSIFICATION:	MISCELLANEOUS CHEMICAL PRODUCTS [2890]
		IRS NUMBER:				042271897
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		TWO SEAPORT LANE SUITE 1300
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02109-1806
		BUSINESS PHONE:		6173450100

	MAIL ADDRESS:	
		STREET 1:		TWO SEAPORT LANE SUITE 1300
		CITY:			BOSTON
		STATE:			MA
		ZIP:			82109

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	CABOT GODFREY L INC
		DATE OF NAME CHANGE:	19680418
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-07-31</periodOfReport>
    <issuer>
        <issuerCik>0000016040</issuerCik>
        <issuerName>CABOT CORP</issuerName>
        <issuerTradingSymbol>CBT</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001243739</rptOwnerCik>
            <rptOwnerName>BERUBE BRIAN A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CABOT CORPORATION, SUITE 1300</rptOwnerStreet1>
            <rptOwnerStreet2>TWO SEAPORT LANE</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02210</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Vice President/General Counsel</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-31</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>12500</value></transactionShares><transactionPricePerShare><value>8.40</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>35802</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><nat
ureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeTransaction><nonDerivativeHolding><securityTitle><value>Common Stock</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>2891</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>Through the Trustee of the Corporation's Retirement Savings Plan.</value></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><derivativeTable><derivativeHolding><securityTitle><value>Series B ESOP Convertible Preferred Stock</value></securityTitle><conversionOrExercisePrice><footnoteId id="F1"/></conversionOrExercisePrice><exerciseDate><footnoteId id="F2"/></exerciseDate><expirationDate><footnoteId id="F2"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>5088</value></und
erlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>35</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>Through the Trustee of the Corporation's Retirement Savings Plan</value></natureOfOwnership></ownershipNature></derivativeHolding></derivativeTable><footnotes><footnote id="F1">Each share is convertible into 146.4 shares of the Corporation's common stock.</footnote><footnote id="F2">Under the Retirement Savings Plan, the Corporation allocates Series B ESOP Convertible Preferred Stock to each participant's account on a quarterly basis.  Subject to certain terms and conditions of the Retirement Savings Plan, participants may elect to receive distributions of their vested account balance in the form of shares of the Corporation's common stock or cash.  Generally, a participant is 20% vested in his account after 2 years of serv
ice with the Corporation; 40% vested after 3 years of service; 60% vested after 4 years of service; and 100% vested after 5 years of service.</footnote></footnotes><remarks/><ownerSignature><signatureName>Michaela Allbee, pursuant to a power of attorney from Brian Berube</signatureName><signatureDate>2003-08-04</signatureDate></ownerSignature></ownershipDocument>

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</SEC-DOCUMENT>
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