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                                                                    EXHIBIT 10.1
[Nasdaq Logo]

Steven J. Randich
Executive Vice President
Chief Technology Officer

                                                April  27, 2001
Mr. Robert Warshaw
Chief Executive Officer
OptiMark Holdings, Inc.
10 Exchange Place, 24th Floor
Jersey City, NJ  07302

Dear Bob:

As you are well aware, The Nasdaq Stock Market, Inc. ("Nasdaq") has determined
that a dual development track for SuperMontage (i.e. "Plan B") is no longer
consistent with our business needs. Based on conversations between Nasdaq and
OptiMark Holdings, Inc. ("OptiMark") that have occurred over the past month or
so, led by Dan Moore and Hector Olmeda, respectively, we have collectively
identified a workable alternative. This alternative provides for staff
augmentation of Nasdaq's Multiple Parallel Architecture ("MPA") design,
development and implementation teams with qualified OptiMark resources. We
believe that through staff augmentation, knowledge transfer, and other technical
assistance from OptiMark, the success of our MPA development effort will be
enhanced.

On October 2, 2000, Nasdaq and OptiMark entered into a Services and License
Agreement (the "Agreement") that provided, in part, for Nasdaq to utilize
OptiMark's development resources as an alternative development track for
Nasdaq's SuperMontage system. Given the newly agreed upon work approach, we
hereby request your agreement with respect to the following amendment to the
Agreement, effective as of the date first set forth above, that will allow
Nasdaq to continue utilizing OptiMark's development resources on new projects:

         1.   Phases and Stages of the SuperMontage Effort. Attachment 8 and
              Section 4 of the Agreement are deleted in their entirety and
              replaced with the scope of services set forth in the attached Task
              Order ("New Services"). The second sentence of Section 5.4 and the
              last line of Section 28.1 (the reference to Attachment 8) are also
              deleted. The Task Order may not be modified except with the prior
              written consent of Nasdaq and OptiMark.

         2.   Nasdaq Payments. Section 7 of the Agreement is deleted in its
              entirety and replaced with the following:

         (a)      Within five (5) days prior to the beginning of each month,
                  OptiMark shall provide Nasdaq with a work plan (the "Monthly
                  Work Plan") that sets forth the services to be performed in
                  the upcoming month. The parties agree that the value of such
                  services (such value to be determined on a time and materials
                  basis pursuant to the rates listed in Attachment 2) should
                  equal approximately $700,000 per month. Further, each Monthly
                  Work Plan shall include the following information with respect
                  to each OptiMark employee or subcontractor who is expected to
                  perform work in support of any of the New Services to be
                  provided to Nasdaq during the month: (i) name; (ii) title;
                  (iii) rate (as listed in
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                  Attachment 2); (iii) number of hours expected to be worked
                  during the month; and (iv) the New Services expected to be
                  performed during the month. Nasdaq shall have four (4) days
                  following its receipt of the Monthly Work Plan to notify
                  OptiMark of any modifications it has to the Monthly Work Plan
                  and the Monthly Work Plan shall be modified accordingly,
                  subject to OptiMark accepting such modifications. OptiMark
                  will provide the services pursuant to the Monthly Work Plan,
                  as may be modified. If Nasdaq does not communicate any
                  modifications within such four (4) day period, then the
                  Monthly Work Plan shall be deemed acceptable to Nasdaq, such
                  acceptance shall be subject to Nasdaq confirming to OptiMark
                  that it received the Monthly Work Plan. OptiMark shall then
                  provide the New Services to Nasdaq in accordance with the
                  Monthly Work Plan, as modified.

         (b)      Within five (5) days prior to the beginning of each month,
                  OptiMark shall also provide Nasdaq with an invoice for the
                  upcoming month (the "Invoice") in the amount of the Monthly
                  Payment (as defined below), as such amount may be adjusted in
                  accordance with the provisions set forth in Section 2(d)
                  hereof. For purposes of clarification, each Invoice should
                  reflect the amount set forth in the Nasdaq approved Monthly
                  Work Plan with a deduction for any Carryover Value from the
                  previous month.

         (c)      Within five (5) days following the end of each month, OptiMark
                  shall provide Nasdaq with a report (the "Monthly Report") that
                  sets forth the following information with respect to each
                  OptiMark employee or subcontractor who performed work in
                  support of any of the New Services provided to Nasdaq during
                  the month: (i) name; (ii) title; (iii) rate (as listed in
                  Attachment 2); (iii) actual number of hours worked during the
                  month; and (iv) the New Services performed during the month.

         (d)      Subject to Nasdaq's approval of the Monthly Work Plan and its
                  receipt of the Invoice, both for the upcoming month, and the
                  Monthly Report for the prior month, Nasdaq shall pay OptiMark
                  a fee as reflected in the Invoice for the New Services (the
                  "Monthly Payment") provided through December 31, 2001;
                  provided, however, that if the value of the New Services
                  provided to Nasdaq in any given month (such value to be
                  determined on a time and materials basis pursuant to the rates
                  listed in Attachment 2) is less than the amount of the Monthly
                  Payment remitted to OptiMark at the beginning of such month
                  (the amount by which the Monthly Payment exceeds the value of
                  the New Services shall be referred to herein as the "Carryover
                  Value"), then OptiMark shall reflect the amount of such
                  Carryover Value on the Invoice for the next succeeding month
                  and Nasdaq shall deduct the amount of the Carryover Value from
                  the Monthly Payment due to OptiMark for the next succeeding
                  month. For purposes of clarification, if Nasdaq modifies the
                  Monthly Work Plan (as permitted pursuant to Section 2(a)) such
                  that the value of the New Services as set forth in the
                  modified Monthly Work Plan is different than the value set
                  forth in the Monthly Work Plan originally delivered by
                  OptiMark, then the modified value shall be used to calculate
                  the Carryover Value. OptiMark shall reimburse Nasdaq for any
                  remaining
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                  Carryover Value that exists as of December 31, 2001. It is
                  further agreed by the parties that if, at any time, the
                  cumulative value of the Carryover Values exceeds $700,000,
                  then Nasdaq shall have the right to terminate the Agreement
                  pursuant to Section 9 hereof and OptiMark shall reimburse
                  Nasdaq for any remaining Carryover Value that exists as of the
                  date of termination. The Carryover Value shall not include
                  deficiencies in time or work that are caused by Nasdaq's
                  failure to provide information, software, and/or support
                  associated with the Monthly Work Plan in a timely manner.
                  OptiMark's decision to not perform work in view of the
                  foregoing sentence shall not be made without consultation with
                  Nasdaq.

         (e)      Nasdaq will inspect an OptiMark deliverable and/or service
                  under the Task Order to determine whether, in the reasonable
                  opinion of Nasdaq, the deliverable and/or service is
                  reasonably acceptable. Nasdaq will make this determination
                  based on whether the deliverable and/or service substantially
                  meets (a) the applicable specifications provided to OptiMark,
                  if any; or (b) the work described in the Monthly Work Plan (as
                  may be modified by Nasdaq).

                           (i) If the deliverable and/or service is not
                  accepted, then Nasdaq promptly will advise OptiMark in writing
                  as to which aspect of the deliverable and/or service needs
                  correcting. OptiMark will seek to remedy such aspect and
                  deliver a corrected deliverable and/or service to Nasdaq on a
                  date to be agreed to by Nasdaq and OptiMark.

                           (ii) Following receipt of the corrected deliverable
                  and/or service, Nasdaq will inspect the deliverable and/or
                  service again. If Nasdaq does not accept the corrected
                  deliverable and/or service, then OptiMark will issue a credit
                  on its next Invoice to Nasdaq for the amounts paid for the
                  deliverable and/or service. If Nasdaq accepts the corrected
                  deliverable and/or service, then Nasdaq will pay OptiMark for
                  the original work. Nasdaq will also pay OptiMark for remedial
                  work performed on the deliverable to correct normal and
                  reasonable development errors; provided, however, that the
                  amount to be paid by Nasdaq for such remedial work shall be
                  included as part of OptiMark's next Invoice and will be part
                  of, rather than in addition to, the $700,000 per month Monthly
                  Payment which the parties anticipate that Nasdaq will pay to
                  OptiMark for the provision of New Services. As for remedial
                  work performed on the deliverable to correct other errors,
                  OptiMark and Nasdaq will mutually agree whether OptiMark
                  should be paid for such remedial work. If they cannot so
                  agree, either party may seek alternative dispute resolution
                  pursuant to Section 25 of the Agreement to make this
                  determination. All payments by Nasdaq under this sub-section
                  will be made with its next Monthly Payment.

         (f)      Subject to provisions set forth in Section 2(d) and in this
                  Section 2(f), Nasdaq will make payment via wire transfer
                  within fifteen (15) calendar days after its receipt of the
                  Invoice. If Nasdaq reasonably disputes any item or amount set
                  forth on the Invoice (including, without limitation, the
                  amount of the Carryover Value), Nasdaq will pay all amounts
                  not in dispute; provided, however, that disputed items
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                  and/or amounts covered in Section 2(e) will be paid as set
                  forth in the current Invoice, subject to OptiMark and Nasdaq
                  adjusting for amounts in dispute in a later Invoice as
                  provided in Section 2(e). OptiMark will maintain accurate and
                  complete records as to time spent in its performance of the
                  New Services and will allow Nasdaq to examine its records from
                  time to time upon written request, with reasonable notice and
                  during normal business hours, in order that Nasdaq may
                  ascertain the correctness of invoices submitted by OptiMark.
                  Late payments shall bear daily interest at a rate of 1.5% per
                  month.

         (g)      OptiMark shall provide Nasdaq with a twenty (20) percent
                  monthly discount for New Services performed over $840,000 in a
                  given month.

         3.   Term and Termination. The term of the Agreement shall continue in
              full effect until December 31, 2001 unless terminated in
              accordance with Section 19 of the Agreement; provided, however,
              that if Nasdaq terminates the Agreement, except for a termination
              pursuant to Section 9 hereof, prior to December 31, 2001, it shall
              remain obligated to make Monthly Payments of $700,000 to OptiMark
              through December 31, 2001.

         4.   Nasdaq Investments. In consideration of the promises set forth
              herein, OptiMark agrees that all Nasdaq warrants (the "Warrants")
              set forth in Section 2(b)-(f) of the 1998 Warrant Agreement and as
              further described in Section 18.1 of the Agreement, shall fully
              vest as of December 31, 2001 without regard to the Critical
              Milestones listed in the Agreement; provided, however, that
              OptiMark has earned minimum cumulative Monthly Payments under the
              Agreement of at least $7,700,000 for New Services performed
              through December 31, 2001 (except that if OptiMark has failed to
              earn cumulative Monthly Payments of at least $7,700,000 due to
              OptiMark's material breach hereof for which Nasdaq has terminated
              the Agreement pursuant to Section 9 hereof, then, the Warrants
              shall, nevertheless, fully vest as of December 31, 2001). The
              exercise date shall remain as stated in Section 18.1 of the
              Agreement. In addition to the obligations set forth in Section
              26.10 of the Agreement, this provision shall also survive any
              termination or cancellation.

         5.   Exclusivity. The first sentence of Section 13.1 of the Agreement
              is deleted in its entirety and replaced with the following:
              OptiMark (including any Affiliates) shall not directly or
              indirectly (including permitting a licensee or owner of any
              OptiMark intellectual property the right to) create or market
              systems or services anywhere in the world for any customer in any
              Financial Instrument, without at least fifteen (15) days prior
              Notice to Nasdaq and subject to Nasdaq's right to consent in each
              instance, such consent shall not be unreasonably withheld or
              delayed.

         6.   Attachment 6 is amended by adding the following at the end of
              thereof:

              "Swaps, equity indices, index options, Eurodollar futures and
              spread market, Eurodollar options, government bonds, corporate
              bonds, interest rate swaps and FRA markets, B2B products, mortgage
              backed securities, stock loan, and options exchange."
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         7.   A new Section 11.7 is added:

              "EXCEPT AS EXPRESSLY SET FORTH HEREIN, OPTIMARK AND ITS AFFILIATES
              DO NOT MAKE ANY OTHER REPRESENTATIONS OR WARRANTIES WITH RESPECT
              TO THE SOFTWARE, OTHER TECHNOLOGY, OR SERVICES PROVIDED HEREUNDER.
              OPTIMARK AND ITS AFFILIATES EXPRESSLY DISCLAIM ALL OTHER
              REPRESENTATIONS AND WARRANTIES, EXPRESS OR IMPLIED, INCLUDING ANY
              IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A SPECIFIC
              PURPOSE."

         8.   The following is inserted after "Consequential Damages." as the
              first sentence of Section 26.8:

              "THE ENTIRE LIABILITY OF OPTIMARK AND ITS AFFILIATES TO NASDAQ OR
              ANY THIRD PARTY ARISING OUT OF OR IN CONNECTION WITH THIS
              AGREEMENT, OR USE OF THE SOFTWARE OR ANY OTHER TECHNOLOGY OR
              SERVICES PROVIDED BY OPTIMARK UNDER THIS AGREEMENT, HOWEVER CAUSED
              AND ON ANY THEORY OF LIABILITY, INCLUDING CONTRACT, STRICT
              LIABILITY, NEGLIGENCE OR OTHER TORT, SHALL BE LIMITED TO * . This
              Section 26.8, as amended, is effective as of October 2, 2000."

         9.   Section 19.2 is deleted in its entirety and replaced with the
              following:

              "In the event of a material breach by OptiMark, or if the
              cumulative value of the Carryover Values exceeds $700,000 as
              determined pursuant to Section 2(d) hereof, then Nasdaq shall have
              the right to terminate the Agreement with 10 days Notice (with a
              right to cure within such period, if the breach is curable)."

Except as provided herein, the Agreement will continue in full force and effect
until terminated in accordance with its terms. Nasdaq understands that this
amendment to the Agreement shall not binding on OptiMark until the approval of
its board of directors has been obtained. Please acknowledge your agreement by
signing below.

Bob, we, at Nasdaq, look forward to our renewed working relationship provided by
this newly-defined staff integration plan.

                                         Regards,

                                         /s/ Steven J. Randich

                                         Steven J. Randich

Agreed and Accepted as of this 26th day of April, 2001:

OPTIMARK HOLDINGS, INC.

By:  /s/ Robert J Warshaw
     -------------------------
Name: Robert J Warshaw
Title: CEO

Attachment

* This confidential portion has been omitted and filed separately with the
Commission.
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                          THE NASDAQ STOCK MARKET, INC.
                     AGREEMENT FOR PROFESSIONAL SERVICES NO.
                          TASK ORDER NO. 00001-2001-03

<TABLE>
<CAPTION>
SERVICES PERFORMED FOR                      SERVICES PERFORMED BY
<S>                                         <C>
THE NASDAQ STOCK MARKET, INC.               OPTIMARK, INC.
SYSTEMS ENGINEERING                         10 EXCHANGE PLACE CENTER
80 MERRITT BLVD.                            JERSEY CITY, NEW JERSEY 07302
TRUMBULL, CT 06611                          (201) 536 7121
</TABLE>

                                            PERFORMANCE OF
                                            SERVICES RESTRICTED TO:
                                            SYSTEM ENGINEERING

SCOPE OF WORK - MPA APPLICATION DEVELOPMENT - SYSTEM ENGINEERING - TEST SUPPORT
SERVICES FOR SUPERMONTAGE

The scope of work includes, but is not limited to, provision of the following
services:

*

Based upon the previously defined services, the currently identified tasks with
estimates include:

*



TASK ORDER PROJECT MANAGER

Dan Moore
203-502-6439
dan.moore@nasd.com


* This confidential portion has been omitted and filed separately with the
Commission.