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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0000016040-07-000044.txt : 20070807
<SEC-HEADER>0000016040-07-000044.hdr.sgml : 20070807
<ACCEPTANCE-DATETIME>20070807142804
ACCESSION NUMBER:		0000016040-07-000044
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20070803
FILED AS OF DATE:		20070807
DATE AS OF CHANGE:		20070807

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

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BURNES KENNETT F
		CENTRAL INDEX KEY:			0001201084

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-05667
		FILM NUMBER:		071031080

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		6173450100

	MAIL ADDRESS:	
		STREET 1:		C/O CABOT CORP
		STREET 2:		TWO SEAPORT LN
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02210
</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>2007-08-03</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001201084</rptOwnerCik>
            <rptOwnerName>BURNES KENNETT F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CABOT CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>TWO SEAPORT LANE, SUITE 1300</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>Chairman, CEO and President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-08-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>86000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.80</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>814622</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>30948.1726</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Through the Trustee for the Corporation's Retirement Savings Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents acquisition of shares of restricted stock awarded under Cabot's 2007 long-term incentive program.  Under the terms of the award, the per share purchase price is 30% of the closing market price of Cabot common stock on May 10, 2007 ($13.80), the date the award was approved by the Compensation Committee of Cabot's Board of Directors.  Mr. Burnes was required to pay the purchase price for the shares by August 6, 2007.  Mr. Burnes paid the purchase price on August 3, 2007.</footnote>
        <footnote id="F2">Prior to July 20, 2007, retirement plan contributions made by the Company under the Employee Stock Ownership Plan portion of Cabot's Retirement Savings Plan were made with shares of Series B ESOP Convertible Preferred Stock.  Each share of this preferred stock was convertible into 146.3782 shares of Cabot's common stock.  On July 20, 2007, all of the preferred stock held by the Trustee of the Retirement Savings Plan was converted to common stock.  The amount reported here includes amounts that previously would have been reported under Table II as Series B ESOP Convertible Preferred Stock as well as retirement plan contributions made by the Company under the 401(k) portion of the Retirement Savings Plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Michaela Allbee, pursuant to a Power of Attorney from Kennett Burnes</signatureName>
        <signatureDate>2007-08-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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