-----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,
 CTWd0fo42ehUvvzbsobK5kRvo0phLHqIO4RwlvI+1gEgO4enkc9gZuOM4OGvP+R9
 azljQQsCIZc+sNQabWZ8TQ==

<SEC-DOCUMENT>0000950138-06-000607.txt : 20060808
<SEC-HEADER>0000950138-06-000607.hdr.sgml : 20060808
<ACCEPTANCE-DATETIME>20060808160756
ACCESSION NUMBER:		0000950138-06-000607
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20060804
FILED AS OF DATE:		20060808
DATE AS OF CHANGE:		20060808

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:		061013125

	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_080706ex.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-08-04</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>2006-08-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>46008</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>20.1398</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4873543</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>2006-08-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>28600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>19.7952</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4844943</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 4, 2006, as follows and as described in
 Footnote 2 below:  200 shares at $19.78; 800 at $19.79; 1,300 at $19.80; 1,300 at $19.81; 300 at $19.82; 900 at $19.83;
 1,100 at $19.84; 300 at $19.85; 500 at $19.86; 400 at $19.87; 300 at $19.88; 600 at $19.89; 524 at $19.90; 1,676 at $19.91;
 2,200 at $19.92; 1,400 at $19.93; 1,608 at $19.94; 1,400 at $19.95; 1,500 at $19.96; 300 at $19.97; 500 at $19.98; 1,200 at
 $19.99; 1,700 at $20.00; 700 at $20.01; 200 at $20.02; 700 at $20.03; 400 at $20.04; 900 at $20.05; 1,800 at $20.06; 100 at
 $20.08; 300 at $20.09; 200 at $20.10; 200 at $20.11; 200 at $20.12; 100 at $20.13; 100 at $20.15; 200 at $20.16; and 400 at
 $20.17.</footnote>
        <footnote id="F2">This footnote sets forth additional detail with respect to the transactions described in Footnote 1, as follows: 200 shares
 at $20.18; 200 at $20.19; 200 at $20.22; 200 at $20.23; 500 at $20.24; 100 at $20.25; 543 at $20.26; 257 at $20.27; 300 at
 $20.28; 200 at $20.29; 300 at $20.30; 100 at $20.33; 200 at $20.34; 700 at $20.35; 400 at $20.36; 200 at $20.39; 300 at
 $20.40; 100 at $20.41; 400 at $20.42; 500 at $20.43; 400 at $20.44; 300 at $20.45; 400 at $20.46; 500 at $20.47; 2,000 at
 $20.48; 500 at $20.49; 1,300 at $20.50; 400 at $20.51; 300 at $20.52; 100 at $20.53; 600 at $20.54; 100 at $20.56; 300 at
 $20.57; 956 at $20.58; 344 at $20.59; 1,100 at $20.60; 500 at $20.61; 200 at $20.62; 800 at $20.63; 100 at $20.64; 100 at
 $20.65; 100 at $20.69; and 200 at $20.74. The weighted average sales price for these transactions was $20.1398 per share.</footnote>
        <footnote id="F3">The sales were effected in multiple transactions, at varying prices, on August 7, 2006, as follows and as described in
 Footnote 4 below:  200 shares at $19.64; 300 at $19.65; 200 at $19.66; 600 at $19.67; 600 at $19.68; 1,200 at $19.69; 1,200
 at $19.70; 870 at $19.71; 700 at $19.72; 1,330 at $19.73; 2,700 at $19.74; 1,000 at $19.75; 900 at $19.76; 1,000 at $19.77;
 2,900 at $19.78; 1,700 at $19.79; 1,000 at $19.80; 1,600 at $19.81; 1,000 at $19.82; 600 at $19.83; 1,000 at $19.84; and 500
 at $19.85.</footnote>
        <footnote id="F4">This footnote sets forth additional detail with respect to the transactions described in Footnote 3, as follows:  700 shares
 at $19.86; 1,100 at $19.87; 100 at $19.88; 500 at $19.89; 100 at $19.90; 200 at $19.91; 200 at $19.94; 100 at $19.96; 200 at
 $19.98; 400 at $19.99; 200 at $20.01; 303 at $20.02; 500 at $20.03; 297 at $20.06; 500 at $20.08; and 100 at $20.09.  The
 weighted average sales price for these transactions was $19.7952 per share.</footnote>
    </footnotes>

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