-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 NUbbslSZov/MQknRQzkcIchzibyRMkFiqOM9aj420X5iIQmLcaDDuR+qHp4GjR1Q
 GsDK7W74L8SWSOtwjBBwsw==

<SEC-DOCUMENT>0000016040-05-000062.txt : 20051121
<SEC-HEADER>0000016040-05-000062.hdr.sgml : 20051121
<ACCEPTANCE-DATETIME>20051121160952
ACCESSION NUMBER:		0000016040-05-000062
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050803
FILED AS OF DATE:		20051121
DATE AS OF CHANGE:		20051121

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MCARTHUR JOHN H
		CENTRAL INDEX KEY:			0001242370

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-05667
		FILM NUMBER:		051218154

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		6154956002

	MAIL ADDRESS:	
		STREET 1:		HARVARD BUSINESS SCHOOL
		STREET 2:		FOWLER ROOM 32 SOLDIERS FIELD
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02163

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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2005-08-03</periodOfReport>

    <dateOfOriginalSubmission>2005-08-05</dateOfOriginalSubmission>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001242370</rptOwnerCik>
            <rptOwnerName>MCARTHUR JOHN H</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>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6429.606</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On August 5, 2005, Mr. McArthur filed a Form 4 to report a sale of 3,600 shares of Cabot common stock that took place on August 3, 2005.  The amount of common stock beneficially owned by Mr. McArthur following the transaction was mistakenly reported as 7,143.  After the transaction, Mr. McArthur beneficially owned 6,429.606 shares of Cabot common stock.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Michaela Allbee, pursuant to a power of attorney from John McArthur</signatureName>
        <signatureDate>2005-11-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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