-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 Q/EvHDwdK4DvBHB8iyrmVg==

<SEC-DOCUMENT>0000016040-04-000050.txt : 20040916
<SEC-HEADER>0000016040-04-000050.hdr.sgml : 20040916
<ACCEPTANCE-DATETIME>20040916123517
ACCESSION NUMBER:		0000016040-04-000050
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		2
CONFORMED PERIOD OF REPORT:	20040910
FILED AS OF DATE:		20040916
DATE AS OF CHANGE:		20040916

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Blevi Dirk
		CENTRAL INDEX KEY:			0001302510

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-05667
		FILM NUMBER:		041033239

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		617-345-0100

	MAIL ADDRESS:	
		STREET 1:		C/O CABOT CORPORTION, TWO SEAPORT LANE
		STREET 2:		SUITE 1300
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02210

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>3
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2004-09-10</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000016040</issuerCik>
        <issuerName>CABOT CORP</issuerName>
        <issuerTradingSymbol>CBT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001302510</rptOwnerCik>
            <rptOwnerName>Blevi Dirk</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CABOT CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>TWO SEAPORT LANE</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02210</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>47917</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>26.40</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-05-09</value>
            </exerciseDate>
            <expirationDate>
                <value>2007-05-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>40000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>33.40</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2007-05-13</value>
            </exerciseDate>
            <expirationDate>
                <value>2009-05-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>40000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes></footnotes>

    <remarks>Exhibit 24 -- Power of Attorney</remarks>

    <ownerSignature>
        <signatureName>Michaela Allbee, pursuant to a power of attorney from Dirk Blevi</signatureName>
        <signatureDate>2004-09-16</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
<FILENAME>attach_1.htm
<DESCRIPTION>POWER OF ATTORNEY FROM DIRK BLEVI
<TEXT>
<HTML><BODY><PRE>POWER OF ATTORNEY



 Know all by these presents, that the undersigned hereby constitutes and appoints each of Jane A. Bell, Michaela Allbee and Brian A. Berube, signing singly, the undersigned's true and lawful attorney-in-fact to:



(1)   execute for and on behalf of the undersigned, in the undersigned's capacity as an officer and/or director of Cabot Corporation (the "Company"), Forms 3, 4, and 5 in accordance with Section 16(a) of the Securities Exchange Act of 1934 and the rules thereunder;



(2)   do and perform any and all acts for and on behalf of the undersigned which may be necessary or desirable to complete and execute any such Form 3, 4, or 5 (including executing and filing a Form I.D.), complete and execute any amendment or amendments thereto, and timely file such form with the United States Securities and Exchange Commission and any stock exchange or similar authority; and



(3)   take any other action of any type whatsoever in connection with the foregoing which, in the opinion of such attorney-in-fact, may be of benefit to, in the best interest of, or legally required by, the undersigned, it being understood that the documents executed by such attorney-in-fact on behalf of the undersigned pursuant to this Power of Attorney shall be in such form and shall contain such terms and conditions as such attorney-in-fact may approve in such attorney-in-fact's discretion.



 The undersigned hereby grants to each such attorney-in-fact full power and authority to do and perform any and every act and thing whatsoever requisite, necessary, or proper to be done in the exercise of any of the rights and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally present, with full power of substitution or revocation, hereby ratifying and confirming all that such attorney-in-fact, or such attorney-in-fact's substitute or substitutes, shall lawfully do or cause to be done by virtue of this power of attorney and the rights and powers herein granted.  The undersigned acknowledges that the foregoing attorneys-in-fact, in serving in such capacity at the request of the undersigned, are not assuming, nor is the Company assuming, any of the undersigned's responsibilities to comply with Section 16 of the Securities Exchange Act of 1934.



 This Power of Attorney shall remain in full force and effect until the undersigned is no longer required to file Forms 3, 4, and 5 with respect to the undersigned's holdings of and transactions in securities issued by the Company, unless earlier revoked by the undersigned in a signed writing delivered to the foregoing attorneys-in-fact.  The undersigned hereby revokes any previous powers of attorney delivered to the Company concerning the subject matter hereof.



 IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of this 14th day of August, 2004.





/s/ Dirk Blevi

Signature











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</PRE></BODY></HTML>

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