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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,
 S1N0QJ79q1qnRME5jVmnmqyLy3PSMduqpBPqaLlsBQsjgKYUSmCfhwqYcjUvmnrq
 fEL0MRvkQ6nOHh5+RYfd1g==

<SEC-DOCUMENT>0001102934-03-000052.txt : 20031104
<SEC-HEADER>0001102934-03-000052.hdr.sgml : 20031104
<ACCEPTANCE-DATETIME>20031104113233
ACCESSION NUMBER:		0001102934-03-000052
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031103
FILED AS OF DATE:		20031104

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CABOT MICROELECTRONICS CORP
		CENTRAL INDEX KEY:			0001102934
		STANDARD INDUSTRIAL CLASSIFICATION:	ABRASIVE ASBESTOS & MISC NONMETALLIC MINERAL PRODUCTS [3290]
		IRS NUMBER:				364324765
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		870 NORTH COMMONS DRIVE
		CITY:			AURORA
		STATE:			IL
		ZIP:			60504
		BUSINESS PHONE:		6303755461

	MAIL ADDRESS:	
		STREET 1:		870 N COMMONS DR
		CITY:			AURORA
		STATE:			IL
		ZIP:			60504

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			NOGLOWS WILLIAM P
		CENTRAL INDEX KEY:			0001201094

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-30205
		FILM NUMBER:		03974993

	BUSINESS ADDRESS:	
		STREET 1:		204 OCEAN AVE
		CITY:			MARBLEHEAD
		STATE:			MA
		ZIP:			01945
		BUSINESS PHONE:		7816317893

	MAIL ADDRESS:	
		STREET 1:		204 OCEAN AVE
		CITY:			MARBLEHEAD
		STATE:			MA
		ZIP:			01945
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>c0001201094d20031104f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-11-03</periodOfReport><notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0001102934</issuerCik>
        <issuerName>CABOT MICROELECTRONICS CORP</issuerName>
        <issuerTradingSymbol>CCMP</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001201094</rptOwnerCik>
            <rptOwnerName>NOGLOWS WILLIAM P</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CABOT MICROELECTRONICS CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>870 COMMONS DRIVE</rptOwnerStreet2>
            <rptOwnerCity>AURORA</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60504</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Chairman, President &amp; CEO</officerTitle><otherText></otherText></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeHolding><securityTitle><value>Common Stock</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>12653</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><derivativeTable><derivativeTransaction><securityTitle><value>Stock Options (Right to buy)</value></securityTitle><conversionOrExercisePrice><value>55.37</value></conversionOrExercisePrice><transactionDate><value>2003-11-03</value></transactionDate><deemedExecutionDate></deemedExecutionDate><transactionCoding><transactionFormType>4</transaction
FormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>250000</value></transactionShares><transactionPricePerShare><value>0</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2004-11-03</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>2013-11-03</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>250000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>250000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTabl
e><footnotes><footnote id="F1">Vesting Schedule:
25%   11/03/04
25%   11/03/05
25%   11/03/06
25%   11/03/07</footnote></footnotes><ownerSignature><signatureName>H. Carol Bernstein</signatureName><signatureDate>2003-11-04</signatureDate></ownerSignature></ownershipDocument>

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