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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,
 Cjj1S607bJIEbHKHMpMQOP2rRBv6UXr8eVCukKy3qC9XHMlVGbQBggWZXPslMCad
 XNPFMOFiEtMpXd42Ohzt/g==

<SEC-DOCUMENT>0000099047-07-000003.txt : 20070402
<SEC-HEADER>0000099047-07-000003.hdr.sgml : 20070402
<ACCEPTANCE-DATETIME>20070402113538
ACCESSION NUMBER:		0000099047-07-000003
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20070329
FILED AS OF DATE:		20070402
DATE AS OF CHANGE:		20070402

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Merrill David A
		CENTRAL INDEX KEY:			0001387982

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-21324
		FILM NUMBER:		07736563

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		646-525-3083

	MAIL ADDRESS:	
		STREET 1:		100 WALL STREET
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10005

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NYFIX INC
		CENTRAL INDEX KEY:			0000099047
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER INTEGRATED SYSTEMS DESIGN [7373]
		IRS NUMBER:				061344888
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		100 WALL STREET
		STREET 2:		26TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10005
		BUSINESS PHONE:		212-809-3542

	MAIL ADDRESS:	
		STREET 1:		100 WALL STREET
		STREET 2:		26TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10005

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	TRINITECH SYSTEMS INC
		DATE OF NAME CHANGE:	19940404

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	TRANS AIRE ELECTRONICS INC
		DATE OF NAME CHANGE:	19910916
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-03-29</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000099047</issuerCik>
        <issuerName>NYFIX INC</issuerName>
        <issuerTradingSymbol>nyfx</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001387982</rptOwnerCik>
            <rptOwnerName>Merrill David A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>100 WALL STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10005</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Global Head Client Operations</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-03-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>48169</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>6.228</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>48169</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">NYFIX issued these shares to Mr. Merrill in satisfaction of a provision in Mr. Merrill's January 5, 2007 offer letter that the Company, within three months of his commencement of employment, provide him a restricted stock grant with a value of $300,000 on the date of grant or pay him $300,000 in cash.  These restricted shares vest in 12 months from the date of grant.  Mr. Merrill will forfeit such grant if he is not employed by the Company on the date the award is to vest (unless he is terminated by the Company without Cause, as defined in his January 5, 2007 offer letter).</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Brian Bellardo, by Power of Attorney</signatureName>
        <signatureDate>2007-04-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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