-----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,
 PrPJJUz5yGlGz1l6Vtd2ZyxE8+qyzmVI4qLXEDMDSQiheJG2XIOvaNqix4QCrvck
 8o/GXIfOdGl9OfHAuIMTVw==

<SEC-DOCUMENT>0001102934-03-000055.txt : 20031105
<SEC-HEADER>0001102934-03-000055.hdr.sgml : 20031105
<ACCEPTANCE-DATETIME>20031105173234
ACCESSION NUMBER:		0001102934-03-000055
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031103
FILED AS OF DATE:		20031105

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:			FULLER H LAURANCE
		CENTRAL INDEX KEY:			0001187553

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-30205
		FILM NUMBER:		03980420

	BUSINESS ADDRESS:	
		STREET 1:		MOTOROLA, INC.
		STREET 2:		1303 EAST ALGONQUIN ROAD
		CITY:			SCHAUMBURG
		STATE:			IL
		ZIP:			60196
		BUSINESS PHONE:		8475765000

	MAIL ADDRESS:	
		STREET 1:		MOTOROLA, INC.
		STREET 2:		1303 EAST ALGONQUIN ROAD
		CITY:			SCHAUMBURG
		STATE:			IL
		ZIP:			60196
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>c0001187553d20031105f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
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<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>0001187553</rptOwnerCik><rptOwnerName>FULLER H LAURANCE</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>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle></officerTitle><otherText></otherText></reportingOwnerRelationshi
p></reportingOwner><nonDerivativeTable><nonDerivativeHolding><securityTitle><value>Common Stock</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>2000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><derivativeTable><derivativeHolding><securityTitle><value>Stock Options (Right to buy)</value></securityTitle><conversionOrExercisePrice><value>38.34</value></conversionOrExercisePrice><exerciseDate><value>2004-03-11</value></exerciseDate><expirationDate><value>2013-03-11</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>7500</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>7500</value><
/sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Stock Options (Right to buy)</value></securityTitle><conversionOrExercisePrice><value>45.49</value></conversionOrExercisePrice><exerciseDate><value>2003-06-17</value></exerciseDate><expirationDate><value>2012-06-17</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>22500</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>22500</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeHoldi
ng><derivativeHolding><securityTitle><value>Phantom Stock</value></securityTitle><conversionOrExercisePrice><value>50.95</value></conversionOrExercisePrice><exerciseDate><value>2003-06-17</value></exerciseDate><expirationDate><value>2003-06-17</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>1233.4543</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1233.4543</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeHolding><derivativeTransaction><securityTitle><value>Phantom Stock</value></securityTitle><conversionOrExercisePrice><value>52.5</value></conversionOrExercisePrice><transactionDate><value>2003-11-05</value></transactionDate><deemedExecutionDate></
deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>J</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionAmounts><transactionShares><value>19.0476</value></transactionShares><transactionPricePerShare><value>0</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2003-11-05</value></exerciseDate><expirationDate><value>2003-11-05</value><footnoteId id="F2"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>19.0476</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>19.0476</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwner
ship><value></value></natureOfOwnership></ownershipNature></derivativeTransaction><derivativeTransaction><securityTitle><value>Phantom Stock</value></securityTitle><conversionOrExercisePrice><value>55.37</value></conversionOrExercisePrice><transactionDate><value>2003-11-03</value></transactionDate><deemedExecutionDate></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>J</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionAmounts><transactionShares><value>162.5429</value></transactionShares><transactionPricePerShare><value>0</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2003-11-03</value></exerciseDate><expirationDate><value>2003-11-03</value><footnoteId id="F2"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSe
curityShares><value>162.5429</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>162.5429</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeTransaction><derivativeHolding><securityTitle><value>Phantom Stock</value></securityTitle><conversionOrExercisePrice><value>59.05</value></conversionOrExercisePrice><exerciseDate><value>2003-09-24</value></exerciseDate><expirationDate><value>2013-09-24</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityValue><value>50.8044</value></underlyingSecurityValue></underlyingSecurity><postTransactionAmounts><valueOwnedFollowingTransaction><value>50.8044</value></valueOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><direc
tOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeHolding></derivativeTable><footnotes><footnote id="F1">Rights to acquire shares pursuant to Directors' Deferred Compensation Plan adopted March 12, 2001 as amended June 17, 2003.</footnote><footnote id="F2">Rights to aquire shares pursuant to Directors' Deferred Compensation Plan are already earned.</footnote></footnotes><ownerSignature><signatureName>H. Laurance  Fuller</signatureName><signatureDate>2003-11-05</signatureDate></ownerSignature></ownershipDocument>

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