Exhibit 10.16

                          INSTRUMENT OF AMENDMENT



         INSTRUMENT OF AMENDMENT, effective as of November 1, 2000 (the
"Amendment"), between NATIONAL ASSOCIATION OF SECURITIES DEALERS, INC. (the
"Association") and FRANK G. ZARB ("Zarb") to the employment agreement
effective on February 24, 1997, as amended effective March 18, 1998, and
subsequently amended as of August, 1999, on March 30, 2000, and as of July
27, 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 Employment Agreement will continue in effect until
February 24, 2001, unless earlier terminated in accordance with its terms;

         WHEREAS, Paragraph 4 of the Employment Agreement provides that the
Employment Agreement may be extended beyond such stated term by written
agreement of Zarb and the Association;

         WHEREAS, the Association and Zarb desire to amend the Employment
Agreement to extend the Employment Agreement for one year beyond such
stated term to allow the Association to select and appoint an individual to
succeed Zarb as the Chairman and Chief Executive Officer of The Nasdaq
Stock Market, Inc. and to provide a transition period for such succession,
and, in addition, to amend the Employment Agreement as otherwise provided
herein;

         WHEREAS, the Employment Agreement provides that the Association
shall provide Zarb with certain post-retirement benefits for a period of
three years after the completion of the term of the Employment Agreement in
exchange for his agreement to provide certain post-retirement consulting
services during such three-year period; and

         WHEREAS, the Association and Zarb wish to modify the Employment
Agreement to extend the period in which the Association shall provide Zarb
with such post-retirement benefits and in which Zarb shall provide such
post-retirement consulting services to the Association for two years beyond
such stated term, 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 amended hereby
               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 to
                  continue to pay and provide Zarb the compensation and
                  benefits otherwise provided for in this Agreement for the
                  remainder of the Term. Zarb agrees to make himself
                  available for the balance of the Term upon reasonable
                  prior notice to provide consulting 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 amended hereby
               to read, in its entirety, as follows:

                         "(a) The Association shall pay Zarb for his
                  services hereunder an annual base salary of: (i)
                  $1,200,000 from the commencement of the Term (as defined
                  in Paragraph 3) through October 31, 2000, and (ii)
                  $2,000,000 during the period commencing on November 1,
                  2000 through the remainder of the Term (as defined in
                  Paragraph 3), which annual base salary shall be payable
                  during the year in approximately equal periodic
                  installments as may be agreed upon by the Association and
                  Zarb. In addition, the Association shall annually pay
                  Zarb such incentive compensation as the Management
                  Compensation Committee of the Association may award in
                  its discretion, provided that the amount of such
                  compensation for each full year of service during the
                  Term (as defined in Paragraph 3) shall not be not less
                  than fifty percent (50%) of Zarb's base salary for such
                  year, and provided further that such compensation for the
                  second year of the Additional Term (as defined in
                  Paragraph 3) shall be no less than $4,000,000.
                  Furthermore, to the extent that the Association grants
                  Zarb stock options prior to the termination of the Term
                  (as defined in Paragraph 3), such options shall fully
                  vest upon the termination of the Term and shall be
                  exercisable during the three (3) month period
                  thereafter."

         3.       The first sentence in Paragraph 2(b) of the Employment
                  Agreement is amended hereby to read, in its entirety,
                  as follows:

                         "(b) Notwithstanding any provision of this
                  Paragraph 2 to the contrary, during the first year of the
                  Additional Term, the aggregate annual base salary and
                  incentive compensation paid to Zarb by the Association
                  shall not be less than such aggregate annual amount paid
                  to Zarb for the second or third year of the Initial Term,
                  whichever was greater."

         4.    Paragraph 2 of the Employment Agreement is further amended
               hereby by adding new subparagraph (c) thereof to read, in
               its entirety, as follows:

                         "(c) Notwithstanding any provision of this
                  Paragraph 2 to the contrary, during the second year of
                  the Additional Term, the aggregate annual base salary and
                  incentive compensation paid to Zarb by the Association
                  shall not be less than such aggregate annual amount paid
                  to Zarb for the third year of the Initial Term or the
                  first year of the Additional Term, whichever was
                  greater."

         5.    Paragraph 3 of the Employment Agreement is amended by
               deleting so much of such paragraph as precedes subparagraph
               (a) thereof and substituting the following in lieu thereof:

                  "This Agreement shall continue in effect for an initial
                  term of three (3) years from the Effective Date (the
                  "Initial Term") and for an additional two (2) years
                  commencing immediately upon the close of the Initial Term
                  (the "Additional Term"), and the Initial Term together
                  with the Additional Term shall be referred to herein as
                  the "Term," subject to earlier termination in one of the
                  following ways:"

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

                         "(b) Upon completion of the Term and for a period
                  of five years thereafter, the Association 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 or employee of the
                  Association or as a fiduciary of any benefit plan of the
                  Association; and further upon completion of the Term and
                  for a period of five years thereafter, Zarb shall be
                  entitled to receive at the Association'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 Association 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 Association 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
                  Association 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 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
                  Association and Zarb; and provided further that Zarb's
                  receipt of the benefits described in 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."

         7.    Paragraphs 5(c) and (d) of the Employment Agreement are
               further amended hereby to read, in their entirety, as
               follows:

                         "(c) Upon completion of the Term and in
                  consideration of the Association's agreement to provide
                  the benefits described in subparagraph (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
                  Association 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).

                         (d) Notwithstanding the foregoing, the obligations
                  of the Association and Zarb under subparagraphs (b) and
                  (c) above shall cease prior to the end of the five year
                  period reflected in subparagraph (c) if Zarb commences
                  employment with another employer (or if Zarb becomes
                  re-employed by the Association)."

         8.    The first sentence of Paragraph 10(b) of the Employment
               Agreement is hereby amended to read in its entirety as
               follows:

                         "(b) If Zarb transfers his principal residence
                  from the Washington, D.C., metropolitan area to the New
                  York City metropolitan area in connection with his
                  employment under this Agreement, the Association shall
                  reimburse Zarb for: (i) moving expenses (within the
                  meaning of Section 217(b) of the Internal Revenue Code)
                  incurred in connection with the establishment of his
                  principal residence in the New York City metropolitan
                  area and the establishment of any interim residence in
                  the New York City metropolitan area prior to the
                  establishment of his principal residence; (ii) airfare
                  expenses incurred by Zarb and Zarb's wife in connection
                  with locating and establishing such residences in the New
                  York City metropolitan area; (iii) the cost of installing
                  and maintaining a T1-line telephone system connected to
                  the telephone system of the Association and, to ensure
                  his personal safety, the cost of installing and
                  maintaining a home security system in each of his
                  residences in the New York City metropolitan area and
                  Florida (if recommended by an independent security
                  study); (iv) the cost of an appropriate efficiency
                  apartment in the Washington D.C., metropolitan area
                  during the remaining Term; and (v) the cost of an
                  appropriate corporate apartment in the Borough of
                  Manhattan, New York City during the remaining Term."

         9.    Paragraph 12 of the Employment Agreement is hereby amended
               to read, in its entirety, as follows:

                         "The Association shall reimburse 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."

         10.   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 and, to
               the extent applicable, for five years thereafter.

         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 November 1, 2000.


                                             NATIONAL ASSOCIATION OF SECURITIES
                                               DEALERS, INC.


_____________________                        By_____________________________
Date                                            Chairman of the Management
                                                Compensation Committee


                                                (Corporate Seal)


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