-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 FdScKo0KLguaQHYnMaWqqwWex3QGT61Nfl8HdFhM83wWWnxYutWG815cvC7JFQ7r
 fa17nk1JBCHzkw2avkdV+w==

<SEC-DOCUMENT>0000950138-06-000652.txt : 20060828
<SEC-HEADER>0000950138-06-000652.hdr.sgml : 20060828
<ACCEPTANCE-DATETIME>20060828142022
ACCESSION NUMBER:		0000950138-06-000652
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20060824
FILED AS OF DATE:		20060828
DATE AS OF CHANGE:		20060828

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:		90 INDUSTRIAL WAY
		CITY:			WILMINGTON
		STATE:			MA
		ZIP:			01887
		BUSINESS PHONE:		978-284-4000

	MAIL ADDRESS:	
		STREET 1:		90 INDUSTRIAL WAY
		CITY:			WILMINGTON
		STATE:			MA
		ZIP:			01887

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			EMERSON ELECTRIC CO
		CENTRAL INDEX KEY:			0000032604
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRONIC & OTHER ELECTRICAL EQUIPMENT (NO COMPUTER EQUIP) [3600]
		STATE OF INCORPORATION:			MO
		FISCAL YEAR END:			0930

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-23621
		FILM NUMBER:		061058186

	BUSINESS ADDRESS:	
		STREET 1:		8000 W FLORISSANT AVE
		STREET 2:		P O BOX 4100
		CITY:			ST LOUIS
		STATE:			MO
		ZIP:			63136
		BUSINESS PHONE:		3145532000

	MAIL ADDRESS:	
		STREET 1:		8000 W. FLORISSANT
		STREET 2:		P.O. BOX 4100
		CITY:			ST LOUIS
		STATE:			MO
		ZIP:			63136

	FORMER NAME:	
		FORMER CONFORMED NAME:	EMERSON ELECTRIC MANUFACTUING CO
		DATE OF NAME CHANGE:	19730710
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4_082506ex.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-08-24</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001049502</issuerCik>
        <issuerName>MKS INSTRUMENTS INC</issuerName>
        <issuerTradingSymbol>MKSI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000032604</rptOwnerCik>
            <rptOwnerName>EMERSON ELECTRIC CO</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>8000 W. FLORISSANT AVE.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ST LOUIS</rptOwnerCity>
            <rptOwnerState>MO</rptOwnerState>
            <rptOwnerZipCode>63136</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-08-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>24454</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>20.3043</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4346999</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Through a subsidiary</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-08-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>29600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>20.1632</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4317399</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Through a subsidiary</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-08-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F4"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>200000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F5"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4117399</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Through a subsidiary</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1065182</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The sales were effected in multiple transactions, at varying prices, on August 24, 2006, as follows: 500 shares at $20.23;
 3,583 at $20.24; 3,400 at $20.25; 1,000 at $20.26; 771 at $20.27; 1,100 at $20.28; 1,000 at $20.29; 3,501 at $20.30; 800 at
 $20.31; 1,299 at $20.32; 1,000 at $20.33; 200 at $20.34; 800 at $20.35; 200 at $20.36; 600 at $20.37; 874 at $20.38; 1,526
 at $20.39; 1,200 at $20.40; 600 at $20.41; 400 at $20.42; and 100 at $20.44. The weighted average sales price for these
 transactions was $20.3043 per share.</footnote>
        <footnote id="F2">The sales were effected in multiple transactions, at varying prices, on August 25, 2006, as follows and as described in
 Footnote 3 below:  100 shares at $19.87; 100 at $19.89; 72 at $19.91; 200 at $19.92; 100 at $19.93; 700 at $19.94; 700 at
 $19.95; 703 at $19.96; 195 at $19.97; 1,023 at $19.98; 300 at $19.99; 775 at $20.00; 132 at $20.01; 600 at $20.02; 400 at
 $20.03; 400 at $20.04; 300 at $20.06; 200 at $20.07; 100 at $20.08; 866 at $20.09; 1,034 at $20.10; 500 at $20.11; 200 at
 $20.12; 600 at $20.13; 500 at $20.14; and 800 at $20.15.</footnote>
        <footnote id="F3">This footnote sets forth additional detail with respect to the transactions described in Footnote 2, as follows:  1,900
 shares at $20.16; 983 at $20.17; 2,117 at $20.18; 2,100 at $20.19; 1,600 at $20.20; 900 at $20.21; 491 at $20.22; 209 at
 $20.23; 200 at $20.24; 100 at $20.25; 1,600 at $20.26; 1,100 at $20.27; 400 at $20.28; 300 at $20.29; 700 at $20.30; 500 at
 $20.31; 400 at $20.33; 300 at $20.34; 300 at $20.37; 300 at $20.39; 300 at $20.41; 100 at $20.43; 300 at $20.44; 200 at
 $20.45; 300 at $20.47; 100 at $20.48; and 200 at $20.52.  The weighted average sales price for these transactions was
 $20.1632 per share.</footnote>
        <footnote id="F4">Bona fide gift to the Emerson Charitable Trust.</footnote>
        <footnote id="F5">Price is not applicable to acquisitions or dispositions resulting from bona fide gifts.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Timothy G. Westman,  Assistant Secretary</signatureName>
        <signatureDate>2006-08-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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