Designated Filer:  Cary Davis
Issuer & Ticker Symbol:  NYFIX, Inc. (NYFX)
Date of Event Requiring Statement:  June 30, 2008

                                                                    Exhibit 99.1

                            Explanation of Responses:


(1) On June 30, 2008, 525,000 shares of common stock, par value $0.001 per share
("Common Stock") of NYFIX, Inc. (the "Issuer") were issued to Warburg Pincus
Private Equity IX, L.P., a Delaware limited partnership ("WP IX"), by the Issuer
in payment of interest and a dividend on the Series B Voting Convertible
Preferred Stock (the "Preferred Stock") required to be paid pursuant to the
Certificate of Designation, a copy of which was attached as Exhibit 3.2 to the
Issuer's current report on Form 8-K filed with the Securities and Exchange
Commission on October 18, 2006. The number of shares of Common Stock issued in
payment of the dividend was determined by dividing (i) the amount of the
dividend that would have been payable with respect to such share of Preferred
Stock had such dividend been paid in cash by (ii) the applicable conversion
price ($5.00) now in effect.

(2) Following the issuance discussed in note 1, WP IX is the direct record owner
of 3,325,227 shares of Common Stock, 1,500,000 shares of Preferred Stock and a
Warrant to purchase an aggregate of 2,250,000 shares of Common Stock (the
"Warrant"). 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. The Preferred Stock is convertible, in whole or in part, at any time and
from time to time at the holder's election. 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. Such conversion rights do not expire. The
exercise price of the Warrant is initially equal to $7.75 per share, subject to
certain adjustments in accordance with the terms of the Warrant. The Warrant is
exercisable 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.

(3) The sole general partner of WP IX is 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"), is the sole member of WP IX LLC.
Warburg Pincus & Co., a New York general partnership ("WP"), is the managing
member of WPP LLC. Warburg Pincus LLC, a New York limited liability company ("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,
as amended (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 disclaims beneficial ownership of all shares of Common Stock
and Preferred Stock, except to the extent of any indirect pecuniary interest
therein.

Mr. Davis, who became a director of the Issuer on October 12, 2006, is a Partner
of WP, and a Member and Managing Director of WP LLC. As such, Mr. Davis may be
deemed to have an indirect pecuniary interest (within the meaning of Rule 16a-1
of the Act) in an indeterminate portion of the securities reported as
beneficially owned by WP IX. Mr. Davis disclaims beneficial ownership of such
securities, except to the extent of any indirect pecuniary interest therein. Mr.
Davis does not directly own the Warrant or any shares of Preferred Stock.