NYFX Nyfix (MM)

Under the Securities Exchange Act of 1934*

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

With a copy to:

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box: o

Note : Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits.  See Rule 240.13d-7 for other parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

* Calculated based on 39,318,320 shares of common stock outstanding as of August 6, 2009, as reported by NYFIX, Inc. in its Form 10-Q for the quarterly period ended June 30, 2009.

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* Calculated based on 39,318,320 shares of common stock outstanding as of August 6, 2009, as reported by NYFIX, Inc. in its Form 10-Q for the quarterly period ended June 30, 2009.

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* Calculated based on 39,318,320 shares of common stock outstanding as of August 6, 2009, as reported by NYFIX, Inc. in its Form 10-Q for the quarterly period ended June 30, 2009.

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* Calculated based on 39,318,320 shares of common stock outstanding as of August 6, 2009, as reported by NYFIX, Inc. in its Form 10-Q for the quarterly period ended June 30, 2009.

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* Calculated based on 39,318,320 shares of common stock outstanding as of August 6, 2009, as reported by NYFIX, Inc. in its Form 10-Q for the quarterly period ended June 30, 2009.

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* Calculated based on 39,318,320 shares of common stock outstanding as of August 6, 2009, as reported by NYFIX, Inc. in its Form 10-Q for the quarterly period ended June 30, 2009.

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* Calculated based on 39,318,320 shares of common stock outstanding as of August 6, 2009, as reported by NYFIX, Inc. in its Form 10-Q for the quarterly period ended June 30, 2009.

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This Amendment No. 8 to Schedule 13D (this “Amendment No. 8”) is being filed with respect to the common stock, par value $0.001 per share (the “Common Stock”), of NYFIX, Inc., a Delaware corporation (the “Issuer”), to amend the Schedule 13D filed on October 19, 2006 (as amended by Amendment No. 1 thereto filed on May 10, 2007, Amendment No. 2 thereto filed on July 3, 2007, Amendment No. 3 thereto filed on January 4, 2008, Amendment No. 4 thereto filed on March 17, 2008, Amendment No. 5 thereto filed on July 2, 2008, Amendment No. 6 thereto filed on January 5, 2009, Amendment No. 7 thereto filed on July 1, 2009 and this Amendment No. 8, the “Schedule 13D”).  Capitalized terms used but not defined herein have the meaning ascribed thereto in the Schedule 13D.

The first sentence of Item 2(b) of the Schedule 13D is hereby amended by replacing it in its entirety with the following:

(b)           The address of the principal business and principal office of each of the Reporting Persons is 450 Lexington Avenue, New York, New York 10017.

Item 4 of the Schedule 13D is hereby amended to add the following at the end of the discussion:

Voting Agreement

NYSE Technologies, Inc. (“Buyer”), a Delaware corporation, CBR Acquisition Corp., a Delaware corporation and a wholly owned subsidiary of Buyer (“Merger Sub”), and Warburg Pincus Private Equity IX, L.P., a Delaware limited partnership (“WP IX”), have entered into a Voting Agreement, dated as of August 26, 2009 (the “Voting Agreement”).

The Voting Agreement provides that, among other things, WP IX has agreed, on the terms and subject to the conditions set forth therein, so long as the Voting Agreement has not been validly terminated in accordance with its terms, that at any meeting of the stockholders of the Issuer, WP IX will be present (in person or by proxy) and it will vote or cause to be voted all of the shares of Common Stock and Series B Preferred Stock beneficially owned by it (a) in favor of approval of (i) that certain Agreement and Plan of Merger (the “Merger Agreement”) by and among Buyer, Merger Sub and the Issuer and the transactions contemplated thereby, including the merger of Merger Sub with and into the Issuer with the Issuer surviving the merger as a wholly owned subsidiary of Buyer (the “Merger”), and (ii) any other matter that is required to facilitate the transactions contemplated by the Merger Agreement; (b) against any Acquisition Proposal (as defined in the Merger Agreement); and (c) against any action or agreement that would impair the ability of Buyer, Merger Sub or the Issuer to complete the Merger, or that would otherwise prevent, impede or delay the consummation of the transactions contemplated by the Merger Agreement, provided that WP IX shall only be required to vote such shares of Common Stock or Series B Preferred Stock on a particular matter set forth in (a), (b)

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Designations.  The Letter Agreement terminates automatically upon the termination of the Merger Agreement.

The foregoing descriptions of the Voting Agreement and Letter Agreement do not purport to be complete and are qualified in their entirety by reference to the Voting Agreement and Letter Agreement, copies of which are attached, respectively, as Exhibits 2 and 3 hereto, and the Voting Agreement and Letter Agreement are incorporated herein in their entirety by reference thereto.  This Amendment No. 8 does not purport to amend, qualify or in any way modify such Voting Agreement or Letter Agreement.

Item 5(a) of the Schedule 13D is hereby amended and restated in its entirety as follows:

(a)           WP IX is the owner of (i) 1,500,000 shares of Series B Preferred Stock, (ii) a Warrant to purchase an aggregate of 2,250,000 shares of Common Stock, subject to adjustment under certain circumstances, and (iii) 4,375,227 shares of Common Stock.  Each share of Series B Preferred Stock is convertible in whole or in part, at any time and from time to time into 10 shares of Common Stock, subject to adjustment under certain circumstances.  The Warrant is exercisable in whole or in part, at any time and from time to time, until October 12, 2016.

Accordingly, as of August 26, 2009, WP IX is deemed to beneficially own an aggregate of 21,625,227 shares of Common Stock, which represents approximately 38.2% of the outstanding shares of Common Stock in accordance with Rule 13d-3(d) under the Exchange Act.  This percentage is based on 39,318,320 shares of Common Stock outstanding as of August 6, 2009, as disclosed in the Issuer’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2009.

Due to their respective relationships with WP IX and each other, the Reporting Persons may be deemed to beneficially own, in the aggregate, 21,625,227 shares of Common Stock, which represents 38.2% of the outstanding shares of Common Stock.  Each of WP, WPP LLC, WP LLC, WP IX LLC, Mr. Kaye and Mr. Landy disclaim beneficial ownership of such Common Stock.

Each of the Reporting Persons may be deemed to be a member of a “group” (as defined in Section 13(d)(3) of the Exchange Act) with Buyer and each of the Reporting Persons hereby disclaims that they are a member of a “group” (as defined in Section 13(d)(3) of the Exchange Act) with Buyer and disclaims beneficial ownership of any shares of Common Stock that may be beneficially owned by Buyer.

Item 5(c) of the Schedule 13D is hereby amended and restated in its entirety as follows:

No transactions in shares of the Issuer’s Common Stock were effected by the Reporting Persons since the filing of Amendment No. 7 to the Schedule 13D on July 1, 2009.

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Item 6 of the Schedule 13D is hereby amended by inserting the following at the end thereof:

As described in Item 4 hereto, (a) WP IX, Buyer and Merger Sub have entered into the Voting Agreement, and (b) WP IX, Buyer and the Issuer have entered into a Letter Agreement. The information set forth in Item 4 with respect to the Voting Agreement and Letter Agreement is incorporated into this Item 6 by reference.

Item 7 is hereby amended by inserting the following at the end thereof:

Exhibit 2. Voting Agreement, dated as of August 26, 2009, by and among NYSE Technologies, Inc., CBR Acquisition Corp. and the stockholders signatory thereto.

Exhibit 3. Letter Agreement, dated as of August 26, 2009, by and among NYSE Technologies, Inc., NYFIX, Inc. and Warburg Pincus Private Equity IX, L.P.

[Remainder of page intentionally left blank]

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SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

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*  Power of Attorney given by Mr. Kaye was previously filed with the SEC on March 2, 2006 as an exhibit to a Schedule 13D filed by Building Products, LLC with respect to Builders FirstSource, Inc.

**  Power of Attorney given by Mr. Landy was previously filed with the SEC on March 2, 2006 as an exhibit to a Schedule 13D filed by Building Products, LLC with respect to Builders FirstSource, Inc.

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