Exhibit 10.17

                          INSTRUMENT OF AMENDMENT



         INSTRUMENT OF AMENDMENT effective as of April 25, 2001 (the
"Amendment"), between NATIONAL ASSOCIATION OF SECURITIES DEALERS, INC. (the
"Association"), The Nasdaq Stock Market, Inc. (the "Nasdaq") and FRANK G.
ZARB ("Zarb") to the employment agreement effective on February 24, 1997,
as subsequently amended effective March 18, 1998, August 20, 1999, March
30, 2000, July 27, 2000 and November 1, 2000, between the Association and
Zarb (the "Employment Agreement").


                            W I T N E S S E T H:

         WHEREAS, the Association and Zarb have entered into the Employment
Agreement;

         WHEREAS, Paragraph 26 of the Employment Agreement provides that
the Employment Agreement may be amended by the mutual consent of the
parties which consent must be evidenced by a document executed with the
same formality as the Employment Agreement;

         WHEREAS, the Association, Zarb and the Nasdaq wish to modify the
Employment Agreement so that the Nasdaq is a party to the Employment
Agreement; and

         WHEREAS, the Association, the Nasdaq and Zarb wish to modify the
Employment Agreement in order to more clearly express the intention to
provide Zarb with certain benefits upon the relinquishment of his duties
and positions as Chairman and Chief Executive Officer of the Association,
and, in addition, to amend the Employment Agreement as otherwise provided
herein.

         NOW, THEREFORE, it is agreed that the Employment Agreement is
hereby amended in the following manner:

         1.    Paragraph 1(b) of the Employment Agreement is hereby amended
               to read, in its entirety, as follows:

                         "(b) The foregoing subparagraph (a) of this
                  Paragraph 1 to the contrary notwithstanding, Zarb shall
                  relinquish his duties or positions as Chairman and Chief
                  Executive Officer of the Association during the
                  Additional Term (as hereinafter defined) if, his
                  successor being duly appointed, the Association and Zarb
                  mutually determine that such relinquishment may
                  facilitate his successor's transition to such office;
                  however, neither such relinquishment nor Zarb's
                  relinquishment of his duties or positions as Chairman and
                  Chief Executive Officer of The Nasdaq Stock Market, Inc.
                  shall be considered a termination of the Term and shall
                  have no effect on the Association's obligation (i) to
                  continue to pay and provide Zarb the compensation and
                  benefits otherwise provided for in this Agreement for the
                  remainder of the Term, including, but not limited to,
                  accruing benefits under the Supplemental Retirement Plan
                  or (ii) effective February 24, 2002, to pay and provide
                  the compensation and benefits to which Zarb would have
                  been entitled upon completion of the Term if he had not
                  earlier relinquished his duties or positions pursuant to
                  this Paragraph 1(b). Zarb agrees to make himself
                  available for the balance of the Term upon reasonable
                  prior notice to provide services to the Association on
                  matters relating to the nature and scope of his duties
                  prior to relinquishment of his duties or positions
                  pursuant to this Paragraph 1(b)."

         2.    Paragraph 2(a) of the Employment Agreement is hereby amended
               by replacing the last sentence thereof with the following:

                         "Furthermore, The Nasdaq Stock Market, Inc. (the
                  "Nasdaq") shall fully vest all stock options granted to
                  Zarb upon the earlier of (i) the termination of the Term
                  or (ii) Zarb's relinquishment of his position and duties
                  pursuant to Paragraph 1(b) and shall permit the exercise
                  of the options during the three (3) month period
                  thereafter for incentive stock options (as defined in
                  Section 422 of the Internal Revenue Code of 1986, as
                  amended) and during the five (5) year period thereafter
                  for all other stock options. Also, the Nasdaq shall cause
                  all restrictions on any restricted stock awarded to Zarb
                  by the Nasdaq to lapse upon the earlier of (i) the
                  termination of the Term or (ii) Zarb's relinquishment of
                  his position and duties pursuant to Paragraph 1(b)."

         3.    Paragraph 5(a) of the Employment Agreement is hereby amended
               to read in its entirety as follows:

                         "(a) Zarb shall be a "Grandfathered Participant"
                  in the National Association of Securities Dealers, Inc.
                  Supplemental Executive Retirement Plan (the "Supplemental
                  Retirement Plan") (capitalized terms used in this
                  Paragraph 5(a), but not otherwise defined in this
                  Agreement shall have the meanings given such terms in the
                  Supplemental Retirement Plan). Upon completion of the
                  Initial Term or as otherwise provided in Paragraphs 6 or
                  7, Zarb shall be entitled to a Retirement Benefit, as if
                  he has fully satisfied the Supplemental Retirement Plan's
                  eligibility and vesting requirements for a full
                  Retirement Benefit. Such Retirement Benefit shall be
                  equal to six percent (6%) of Zarb's Final Average
                  Compensation multiplied by the number of Years of Service
                  attained by Zarb through February 24, 2002, or his
                  earlier termination of employment other than as a result
                  of his relinquishment of his position and duties pursuant
                  to Paragraph 1(b) hereof, less any vested benefit that he
                  accrued under the NASD Retirement Plan. Zarb's Final
                  Average Compensation, for purposes of the Supplemental
                  Retirement Plan, shall be computed for the entire period
                  of his actual service with the Association, including
                  service after his relinquishment of his position and
                  duties pursuant to Paragraph 1(b) hereof. Notwithstanding
                  the foregoing to the contrary, Zarb's Retirement Benefit
                  as aforesaid shall not be less than the supplemental
                  retirement benefit to which he would have been entitled
                  upon his termination of employment under the terms of
                  this Agreement as in effect immediately following the
                  amendment of this Agreement dated March 18, 1998. Except
                  as otherwise provided in Paragraph 6 or 7, Zarb shall not
                  be entitled to receive any Retirement Benefit under this
                  Paragraph 5(a) if his employment with the Association
                  terminates prior to his completion of the Initial Term.
                  The Association shall pay the Retirement Benefit to Zarb
                  in a lump-sum (i) within fifteen (15) days after February
                  24, 2002, (ii) within fifteen (15) days after his earlier
                  termination of employment other than as a result of his
                  relinquishment of his position and duties pursuant to
                  Paragraph 1(b) hereof, or (iii) at such other time as
                  provided in Paragraph 6 or 7."

         4.    Paragraph 5(b) of the Employment Agreement is hereby amended
               to read in its entirety as follows:

                         "On February 24, 2002, unless Zarb earlier
                  terminates his employment, other than as a result of his
                  relinquishment of his position and duties pursuant to
                  Paragraph 1(b) hereof, and for a period of five years
                  thereafter, (X) the Association and the Nasdaq shall
                  indemnify and hold Zarb harmless to the fullest extent
                  permitted by applicable law with regard to any action or
                  inaction of Zarb as an officer, director, employee or
                  consultant of the Association or the Nasdaq or as a
                  fiduciary of any benefit plan of the Association or the
                  Nasdaq and (Y) Zarb shall be entitled to receive at the
                  Nasdaq's expense: (i) the full-time and exclusive use of
                  an automobile of his choice and driver; (ii) appropriate
                  office and secretarial services; (iii) payment or
                  reimbursement of dues, initiation and other fees and
                  charges for various clubs in the New York City and/or
                  Washington, D.C., metropolitan areas upon presentation of
                  appropriate receipts or other documentation (in the case
                  of this clause (iii), not exceeding $20,000 for any
                  year); (iv) upon presentation of appropriate receipts or
                  vouchers in a manner consistent with the expense
                  substantiation policy of the Nasdaq generally applicable
                  to its executive officers and in accordance with the
                  provisions of such policy regarding the timing and amount
                  of expense reimbursements, payment or reimbursement of
                  reasonable business-related expenses incurred, including,
                  but not limited to, expenses for such items as
                  entertainment, travel, hotels, and meals, as well as for
                  the travel, hotel, and meals of Zarb's wife on those
                  occasions when the proper representation of the Nasdaq
                  makes it advisable for her to accompany him, provided
                  that in the case of travel, hotel, and meals for Zarb's
                  wife, the reimbursements provided under this clause (iv)
                  shall include such amounts as may be necessary for Zarb
                  to pay any taxes imposed with respect to such
                  reimbursements (which amounts shall be paid to Zarb by
                  January 31 of the year following the year in which the
                  expenses were incurred); (v) an appropriate efficiency
                  apartment in the Washington D.C. metropolitan area; (vi)
                  an appropriate corporate apartment in the Borough of
                  Manhattan, New York City; (vii) to ensure the personal
                  safety of Zarb and his wife, at such times and as
                  reasonably required by the circumstances, a personal
                  bodyguard for Zarb and his wife and/or surveillance of
                  his personal residences and/or other reasonable method of
                  security; (viii) a T1-line telephone system connected to
                  the telephone system of the Nasdaq and appropriate
                  maintenance thereof and a home security system in each of
                  his residences in the New York City metropolitan area and
                  Florida; and (ix) reimbursement of Zarb for the annual
                  expenses he incurs for personal financial and tax
                  counseling, provided that the amount of such
                  reimbursement for any calendar year shall not exceed
                  $50,000; (x) reimbursement of Zarb for any legal fees and
                  expenses incurred in the negotiation of this Agreement,
                  provided that the amount of such reimbursement for any
                  calendar year shall not exceed $20,000, and, in the event
                  of any dispute between Zarb and the Association and/or
                  the Nasdaq under this Agreement which is wholly or partly
                  resolved in Zarb's favor, reimbursement of Zarb for
                  reasonable legal fees and expenses incurred in connection
                  with such dispute, provided that the reimbursement
                  provided under this clause (x) shall include such amounts
                  as may be necessary for Zarb to pay any taxes imposed
                  with respect to such reimbursements; and (xi) an annual
                  consulting fee of $100,000, which shall be payable during
                  the year in approximately equal periodic installments as
                  may be agreed upon by the Nasdaq and Zarb; and provided
                  further that Zarb's receipt of the benefits described in
                  clause (Y) of this subparagraph (b) shall be contingent
                  upon Zarb's agreement to make himself available to
                  provide the consulting services set forth in subparagraph
                  (c) below."

         5.    Paragraph 5(c) of the Employment Agreement is hereby amended
               to read in its entirety as follows:

                         "On February 24, 2002, unless Zarb earlier
                  terminates his employment, other than as a result of his
                  relinquishment of his position and duties pursuant to
                  Paragraph 1(b) hereof, and in consideration of the
                  Nasdaq's agreement to provide the benefits described in
                  clause (Y) of subparagraph 5(b) above, Zarb agrees to
                  make himself available for a period of five years
                  thereafter upon reasonable prior notice to provide
                  consulting services to the Chief Executive Officer of the
                  Nasdaq on matters relating to the nature and scope of his
                  duties during the Term; provided, however, that in no
                  event shall Zarb be required to provide such consulting
                  services for more than 100 hours during any
                  12-month-period (including travel time associated with
                  such consulting services).

         6.    All of the terms and conditions of the Employment Agreement
               as amended by this Instrument of Amendment shall remain in
               full force and effect throughout the Term thereof.


         IN WITNESS WHEREOF, the corporate party hereto has caused this
Instrument of Amendment to be duly executed and delivered on the date
indicated below, and the individual party hereto has executed and delivered
this Instrument of Amendment on the date indicated below, effective for all
purposes on April 25, 2001.


                                         NATIONAL ASSOCIATION OF SECURITIES
                                           DEALERS, INC.


_____________________                    By_____________________________
Date                                       Chairman of the Management
                                           Compensation Committee


                                          (Corporate Seal)


                                         The Nasdaq Stock Market, Inc.


_____________________                    By_____________________________
Date                                        Chairman of the Management
                                            Compensation Committee

                                            (Corporate Seal)


---------------------                    -------------------------------
Date                                     Frank G. Zarb