<SEC-DOCUMENT>0001181431-12-006878.txt : 20120208
<SEC-HEADER>0001181431-12-006878.hdr.sgml : 20120208
<ACCEPTANCE-DATETIME>20120208180747
ACCESSION NUMBER:		0001181431-12-006878
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20120206
FILED AS OF DATE:		20120208
DATE AS OF CHANGE:		20120208

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SOMMERS DAVID P
		CENTRAL INDEX KEY:			0001232882

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-26251
		FILM NUMBER:		12583402

	MAIL ADDRESS:	
		STREET 1:		310 LITTETON ROAD
		CITY:			WESTFORD
		STATE:			MA
		ZIP:			01886

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NETSCOUT SYSTEMS INC
		CENTRAL INDEX KEY:			0001078075
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER INTEGRATED SYSTEMS DESIGN [7373]
		IRS NUMBER:				042837575
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0331

	BUSINESS ADDRESS:	
		STREET 1:		310 LITTLETON ROAD
		CITY:			WESTFORD
		STATE:			MA
		ZIP:			01886
		BUSINESS PHONE:		978-614-4000

	MAIL ADDRESS:	
		STREET 1:		310 LITTLETON ROAD
		CITY:			WESTFORD
		STATE:			MA
		ZIP:			01886
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rrd333173.xml
<DESCRIPTION>2/04/2012
<TEXT>
<XML>
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    <periodOfReport>2012-02-06</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001078075</issuerCik>
        <issuerName>NETSCOUT SYSTEMS INC</issuerName>
        <issuerTradingSymbol>NTCT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001232882</rptOwnerCik>
            <rptOwnerName>SOMMERS DAVID P</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O NETSCOUT SYSTEMS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>310 LITTLETON ROAD</rptOwnerStreet2>
            <rptOwnerCity>WESTFORD</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01886</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice-Chairman</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
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                <value>Common Stock</value>
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            <transactionDate>
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                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionAmounts>
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                <transactionPricePerShare>
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                </transactionShares>
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    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Unit</value>
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            <transactionDate>
                <value>2012-02-06</value>
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                <transactionCode>M</transactionCode>
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                <footnoteId id="F1"/>
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                    <value>17500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2012-02-06</value>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F8"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>17500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>53663</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
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                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.22</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2012-02-07</value>
            </transactionDate>
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                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F6"/>
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            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F9"/>
            </exerciseDate>
            <expirationDate>
                <value>2012-07-17</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
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                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The shares of Common Stock were acquired upon the vesting of certain Restricted Stock Units previously granted to the reporting person.</footnote>
        <footnote id="F2">Price is N/A.</footnote>
        <footnote id="F3">2,500 of these shares are held by a trust in which the reporting person has a pecuniary interest.</footnote>
        <footnote id="F4">The shares of Common Stock were withheld by the Company to satisfy the reporting person's tax withholding obligation upon the vesting of restricted stock units.  The withheld shares were returned to treasury.</footnote>
        <footnote id="F5">Represents the closing price of the Company's Common Stock on February 3, 2012.</footnote>
        <footnote id="F6">Option was exercised and related Common stock was sold pursuant to a 10b5-1 plan.</footnote>
        <footnote id="F7">The shares sold on this date were sold in multiple transactions. This price is the weighted average sales price per share; the actual sales price per share ranged from $20.98 to $21.22.</footnote>
        <footnote id="F8">Date is N/A.</footnote>
        <footnote id="F9">Option vested over three years in equal quarterly installments. The initial portion of the option grant initially became exercisable on September 13, 2003, and the remainder vested in equal quarterly installments thereafter.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>By: /s/  David P. Sommers</signatureName>
        <signatureDate>2012-02-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
