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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 T8QgGSq/A+up9S4nwUJyQ/l5P+xAmj+2ptqZV/qCwvUnpcUAwiroc6o0WejyK/KM
 H7t6kuSmbljaN4bRYBxPvQ==

<SEC-DOCUMENT>0001049502-03-000037.txt : 20030806
<SEC-HEADER>0001049502-03-000037.hdr.sgml : 20030806
<ACCEPTANCE-DATETIME>20030806104111
ACCESSION NUMBER:		0001049502-03-000037
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030804
FILED AS OF DATE:		20030806

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MKS INSTRUMENTS INC
		CENTRAL INDEX KEY:			0001049502
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL INSTRUMENTS FOR MEASUREMENT, DISPLAY, AND CONTROL [3823]
		IRS NUMBER:				042277512
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		SIX SHATTUCK RD
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810
		BUSINESS PHONE:		9789752350

	MAIL ADDRESS:	
		STREET 1:		SIX SHATTUCK ROAD
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BERTUCCI JOHN R
		CENTRAL INDEX KEY:			0001106180

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-23621
		FILM NUMBER:		03825278

	BUSINESS ADDRESS:	
		STREET 1:		C/O MKS INSTRUMENTS INC
		STREET 2:		SIX SHATTUCK RD
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810
		BUSINESS PHONE:		9789752350

	MAIL ADDRESS:	
		STREET 1:		C/O MKS INSTRUMENTS INC
		STREET 2:		SIX SHATTUCK RD
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>ber99.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
	<periodOfReport>2003-08-04</periodOfReport>
	<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0001049502</issuerCik>
        <issuerName>MKS INSTRUMENTS INC</issuerName>
        <issuerTradingSymbol>MKSI</issuerTradingSymbol>
	</issuer>
	<reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001106180</rptOwnerCik>
            <rptOwnerName>BERTUCCI JOHN R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>50 HILL STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LEXINGTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
			<isDirector>1</isDirector>
			<isOfficer>1</isOfficer>
			<isTenPercentOwner>1</isTenPercentOwner>
			<isOther>0</isOther>
			<officerTitle>President &amp; CEO</officerTitle>
		</reportingOwnerRelationship>
	</reportingOwner>
	<nonDerivativeTable>
		<nonDerivativeTransaction>
			<securityTitle>
				<value>Common</value>
			</securityTitle>
			<transactionDate>
				<value>2003-08-04</value>
			</transactionDate>
			<deemedExecutionDate>
			</deemedExecutionDate>
			<transactionCoding>
				<transactionFormType>4</transactionFormType>
				<transactionCode>S</transactionCode>
				<equitySwapInvolved>0</equitySwapInvolved>
			</transactionCoding>
			<transactionAmounts>
				<transactionShares>
					<value>4000</value>
				</transactionShares>
				<transactionPricePerShare>
					<value>21.43</value>
				</transactionPricePerShare>
				<transactionAcquiredDisposedCode>
					<value>D</value>
					<footnoteId id="F1"/>
				</transactionAcquiredDisposedCode>
			</transactionAmounts>
			<postTransactionAmounts>
				<sharesOwnedFollowingTransaction>
					<value>5099353</value>
				</sharesOwnedFollowingTransaction>
			</postTransactionAmounts>
			<ownershipNature>
				<directOrIndirectOwnership>
					<value>D</value>
				</directOrIndirectOwnership>
				<natureOfOwnership>
					<value/>
				</natureOfOwnership>
			</ownershipNature>
		</nonDerivativeTransaction>
		<nonDerivativeTransaction>
			<securityTitle>
				<value>Common</value>
			</securityTitle>
			<transactionDate>
				<value>2003-08-04</value>
			</transactionDate>
			<deemedExecutionDate>
			</deemedExecutionDate>
			<transactionCoding>
				<transactionFormType>4</transactionFormType>
				<transactionCode>S</transactionCode>
				<equitySwapInvolved>0</equitySwapInvolved>
			</transactionCoding>
			<transactionAmounts>
				<transactionShares>
					<value>4000</value>
				</transactionShares>
				<transactionPricePerShare>
					<value>21.43</value>
				</transactionPricePerShare>
				<transactionAcquiredDisposedCode>
					<value>D</value>
				</transactionAcquiredDisposedCode>
			</transactionAmounts>
			<postTransactionAmounts>
				<sharesOwnedFollowingTransaction>
					<value>5397927</value>
				</sharesOwnedFollowingTransaction>
			</postTransactionAmounts>
			<ownershipNature>
				<directOrIndirectOwnership>
					<value>I</value>
				</directOrIndirectOwnership>
				<natureOfOwnership>
					<value>By Spouse</value>
				</natureOfOwnership>
			</ownershipNature>
		</nonDerivativeTransaction>
		<nonDerivativeHolding>
			<securityTitle>
				<value>Common</value>
			</securityTitle>
			<postTransactionAmounts>
				<sharesOwnedFollowingTransaction>
					<value>4710</value>
				</sharesOwnedFollowingTransaction>
			</postTransactionAmounts>
			<ownershipNature>
				<directOrIndirectOwnership>
					<value>I</value>
				</directOrIndirectOwnership>
				<natureOfOwnership>
					<value>By Limited Partnership</value>
				</natureOfOwnership>
			</ownershipNature>
		</nonDerivativeHolding>
		<nonDerivativeHolding>
			<securityTitle>
				<value>Common</value>
			</securityTitle>
			<postTransactionAmounts>
				<sharesOwnedFollowingTransaction>
					<value>500000</value>
				</sharesOwnedFollowingTransaction>
			</postTransactionAmounts>
			<ownershipNature>
				<directOrIndirectOwnership>
					<value>I</value>
				</directOrIndirectOwnership>
				<natureOfOwnership>
					<value>By Trust</value>
				</natureOfOwnership>
			</ownershipNature>
		</nonDerivativeHolding>
	</nonDerivativeTable>
	<footnotes>
		<footnote id="F1">The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan previously adopted by the reporting person.</footnote>
	</footnotes>
	<remarks>
	</remarks>
	<ownerSignature>
		<signatureName>By: Joseph M.Tocci / POA</signatureName>
		<signatureDate>2003-08-06</signatureDate>
	</ownerSignature>
</ownershipDocument>

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