EX-99

Designated Filer: Warburg Pincus Private Equity IX, L.P.
Issuer & Ticker Symbol:   NYFIX, Inc. (NYFX)
Date of Event Requiring Statement: March 7, 2008



                                                                    Exhibit 99.1

                            Explanation of Responses:


(1) This Form 4 is filed on behalf of Warburg Pincus Private Equity IX, L.P., a
Delaware limited partnership ("WP IX"), Warburg Pincus IX, LLC, a New York
limited liability company ("WP IX LLC"), Warburg Pincus Partners LLC, a New York
limited liability company ("WPP LLC"), Warburg Pincus LLC, a New York limited
liability company ("WP LLC"), Warburg Pincus & Co., a New York general
partnership ("WP"), and Messrs. Charles R. Kaye and Joseph P. Landy
(collectively, the "Reporting Persons").

(2) Following the purchases on March 7 and 10, 2008 of the common stock, par
value $0.001 per share ("Common Stock") of NYFIX, Inc. (the "Issuer"), WP IX is
the direct record owner of 2,789,427 shares of Common Stock and 1,500,000 shares
of Series B Voting Convertible Preferred Stock (the "Preferred Stock"), which is
convertible into 15,000,000 shares of Common Stock. The sole general partner of
WP IX is WP IX LLC. WPP LLC is the sole member of WP IX LLC. WP is the managing
member of WPP LLC. WP LLC manages WP IX. Charles R. Kaye and Joseph P. Landy are
each Managing General Partners of WP and Co-Presidents and Managing Members of
WP LLC. By reason of the provisions of Rule 16a-1 of the Securities Exchange Act
of 1934 (the "Act"), WP, WP LLC, WPP LLC, WP IX LLC, Mr. Kaye and Mr. Landy may
be deemed to be the beneficial owners of any securities that may be deemed to be
beneficially owned by WP IX. Each of WP, WP LLC, WPP LLC, WP IX LLC, Mr. Kaye
and Mr. Landy all disclaim beneficial ownership of all shares of Common Stock
and Preferred Stock except to the extent of any indirect pecuniary interest
therein.

(3) Each share of Preferred Stock is initially convertible into 10 shares of
Common Stock at an initial conversion price of $5.00 per share, subject to
certain adjustments in accordance with the terms of the Preferred Stock.

(4) The Preferred Stock is convertible, in whole or in part, at any time and
from time to time at the holder's election. At any time after April 12, 2008,
the Preferred Stock is convertible at the option of the Issuer, in whole or in
part, if the price per share of the Common Stock reaches certain levels. The
conversion rights do not expire.

(5) The exercise price of the Warrant to Purchase Common Stock (the "Warrant")
is initially equal to $7.75 per share, subject to certain adjustments in
accordance with the terms of the Warrant.

(6) The Warrant is convertible at any time, in whole or in part, at the holder's
option until 5:00 p.m. Eastern Time on October 12, 2016, at which point the
Warrant expires.

(7) WP IX is the direct record owner of the Warrant, which is convertible into
2,250,000 shares of Common Stock. The sole general partner of WP IX is WP IX
LLC. WPP LLC is the sole member of WP IX LLC. WP is the managing member of WPP
LLC. WP LLC manages WP IX. Charles R. Kaye and Joseph P. Landy are each Managing
General Partners of WP and Co-Presidents and Managing Members of WP LLC. By
reason of the provisions of Rule 16a-1 of the Act, WP, WP LLC, WPP LLC, WP IX
LLC, Mr. Kaye and Mr. Landy may be deemed to be the beneficial owners of any
securities that may be deemed to be beneficially owned by WP IX. Each of WP, WP
LLC, WPP LLC, WP IX LLC, Mr. Kaye and Mr. Landy all disclaim beneficial
ownership of the Warrant except to the extent of any indirect pecuniary interest
therein.

EX-99

Designated Filer: Warburg Pincus Private Equity IX, L.P.
Issuer & Ticker Symbol:   NYFIX, Inc. (NYFX)
Date of Event Requiring Statement: March 7, 2008



                                                                    Exhibit 99.2

                        JOINT FILERS' NAMES AND ADDRESSES


1.   Name:    Warburg Pincus IX LLC
     Address: c/o Warburg Pincus LLC
              466 Lexington Avenue
              New York, NY 10017

2.   Name:    Warburg Pincus Partners LLC
     Address: c/o Warburg Pincus LLC
              466 Lexington Avenue
              New York, NY 10017

3.   Name:    Warburg Pincus LLC
     Address: 466 Lexington Avenue
              New York, NY 10017

4.   Name:    Warburg Pincus & Co.
     Address: c/o Warburg Pincus LLC
              466 Lexington Avenue
              New York, NY 10017

5.   Name:    Charles R. Kaye
     Address: c/o Warburg Pincus LLC
              466 Lexington Avenue
              New York, NY 10017

6.   Name:    Joseph P. Landy
     Address: c/o Warburg Pincus LLC
              466 Lexington Avenue
              New York, NY 10017

EX-99

Designated Filer: Warburg Pincus Private Equity IX, L.P.
Issuer & Ticker Symbol:   NYFIX, Inc. (NYFX)
Date of Event Requiring Statement: March 7, 2008



                                                                    Exhibit 99.3

                            JOINT FILERS' SIGNATURES




     WARBURG PINCUS IX, LLC

     By:  Warburg Pincus Partners, LLC, its Sole Member,
          By:  Warburg Pincus & Co., its Managing Member

     By:   /s/  Scott A. Arenare
           ---------------------------                       Date: 03/11/2008
           Name:   Scott A. Arenare
           Title:  Partner



     WARBURG PINCUS PARTNERS, LLC

     By:  Warburg Pincus & Co., its Managing Member

     By:   /s/  Scott A. Arenare
           ---------------------------                       Date: 03/11/2008
           Name:   Scott A. Arenare
           Title:  Partner



     WARBURG PINCUS LLC

      By:   /s/  Scott A. Arenare
           ---------------------------                       Date: 03/11/2008
           Name:   Scott A. Arenare
           Title:  Managing Director



     WARBURG PINCUS & CO.

      By:   /s/  Scott A. Arenare
           ---------------------------                       Date: 03/11/2008
           Name:   Scott A. Arenare
           Title:  Partner



     By:   /s/  Scott A. Arenare
           ---------------------------                       Date: 03/11/2008
           Name:   Charles R. Kaye
           By:     Scott A. Arenare,
                   Attorney-in-Fact*



     By:   /s/  Scott A. Arenare
           ---------------------------                       Date: 03/11/2008
           Name:   Joseph P. Landy
           By:     Scott A. Arenare,
                   Attorney-in-Fact**


*  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.