-----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,
 HIdMIf/KpqgJkwoyT4Y/6D4nSBuQ2yxlvYqirKbapgMCtWxdehBOG/mShyDLWVNo
 SarWTFBq4WlOMy9ENlDC7Q==

<SEC-DOCUMENT>0000950138-06-000565.txt : 20060711
<SEC-HEADER>0000950138-06-000565.hdr.sgml : 20060711
<ACCEPTANCE-DATETIME>20060711161052
ACCESSION NUMBER:		0000950138-06-000565
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20060707
FILED AS OF DATE:		20060711
DATE AS OF CHANGE:		20060711

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:		06956333

	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_071006ex.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-07-07</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>2006-07-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>19.5044</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5322405</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>2006-07-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>17400</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>19.2217</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5305005</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 July 7, 2006, as follows and as described in Footnote
 2 below:  61 shares at $19.18; 71 at $19.21; 168 at $19.22; 200 at $19.23; 200 at $19.24; 1,000 at $19.25; 400 at $19.26;
 1,200 at $19.27; 396 at $19.28; 300 at $19.29; 700 at $19.30; 700 at $19.31; 600 at $19.32; 600 at $19.33; 400 at $19.34;
 299 at $19.35; 200 at $19.37; 100 at $19.39; 464 at $19.44; 119 at $19.45; 117 at $19.46; 100 at $19.47; 400 at $19.48; 491
 at $19.49; 482 at $19.50; 207 at $19.51; 1,028 at $19.52; 970 at $19.53; 619 at $19.54; and 353 at $19.55.</footnote>
        <footnote id="F2">This footnote sets forth additional detail with respect to the transactions described in Footnote 1, as follows:  825 shares
 at $19.56; 642 at $19.57; 900 at $19.58; 955 at $19.59; 400 at $19.60; 723 at $19.61; 741 at $19.62; 709 at $19.63; 1,536 at
 $19.64; 816 at $19.65; 963 at $19.66; 146 at $19.67; 549 at $19.68; 100 at $19.69; 9 at $19.70; 300 at $19.71; 485 at
 $19.72; 300 at $19.73; 595 at $19.74; 120 at $19.75; 200 at $19.76; and 41 at $19.78.  The weighted average sales price for
 these transactions was $19.5044 per share.</footnote>
        <footnote id="F3">The sales were effected in multiple transactions, at varying prices, on July 10, 2006, as follows and as described in
 Footnote 4 below: 2,200 shares at $19.00; 100 at $19.04; 100 at $19.05; 100 at $19.06; 200 at $19.07; 200 at $19.08; 158 at
 $19.09; 200 at $19.10; 300 at $19.11; 100 at $19.12; 156 at $19.13; 600 at $19.14; 42 at $19.15; 844 at $19.16; 200 at
 $19.17; 100 at $19.18; 400 at $19.19; 700 at $19.20; 600 at $19.21; 752 at $19.22; 400 at $19.23; 1,329 at $19.24; and 319
 at $19.25.</footnote>
        <footnote id="F4">This footnote sets forth additional detail with respect to the transactions described in Footnote 3 as follows:  200 shares
 at $19.26; 700 at $19.27; 300 at $19.28; 100 at $19.29; 200 at $19.30; 500 at $19.32; 2,187 at $19.33; 1,100 at $19.34; 100
 at $19.35; 613 at $19.36; 241 at $19.37; 100 at $19.38; 800 at $19.40; and 159 at $19.41.  The weighted average sales price
 for these transactions was $19.2217 per share.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Timothy G. Westman,  Assistant Secretary</signatureName>
        <signatureDate>2006-07-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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