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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 AdEVLbTup8JOAuRtnMBFTGMmDZiwyhYqfyjcgLag7yBpv4WtCEnp8p8VSKrp1g6W
 UU3ISlldCJCiUa/5RsdnFw==

<SEC-DOCUMENT>0001225201-03-000011.txt : 20030909
<SEC-HEADER>0001225201-03-000011.hdr.sgml : 20030909
<ACCEPTANCE-DATETIME>20030909100625
ACCESSION NUMBER:		0001225201-03-000011
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030908
FILED AS OF DATE:		20030909

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			FLAHERTY MICHELLE
		CENTRAL INDEX KEY:			0001232879

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-26251
		FILM NUMBER:		03887186

	MAIL ADDRESS:	
		STREET 1:		3 DAYNA LANE
		CITY:			BUZZARDS BAY
		STATE:			MA
		ZIP:			02532

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:		4 TECHNOLOGY PARK DR
		CITY:			WESTFORD
		STATE:			MA
		ZIP:			01886
		BUSINESS PHONE:		9786144000

	MAIL ADDRESS:	
		STREET 1:		4 TECHNOLOGY PARK DRIVE
		CITY:			WESTFORD
		STATE:			MA
		ZIP:			01886
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>

<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2003-09-08</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001232879</rptOwnerCik>
            <rptOwnerName>FLAHERTY MICHELLE</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>3 DAYNA LANE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BUZZARDS BAY</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02532</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>V.P. Human Resources</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>

        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2003-09-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>5.32</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>926</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>

    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The amount of securities beneficailly owned following reported transactions has been updated to reflect transactions that are no longer required to be reported.</footnote>
    </footnotes>


    <ownerSignature>
        <signatureName>Michelle Flaherty</signatureName>
        <signatureDate>2003-09-08</signatureDate>
    </ownerSignature>

</ownershipDocument>

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