PURCHASE AGREEMENT

     U.S. Wireless Data, Inc. (the "Company") and Tonga Partners, L.P. ("Tonga")
hereby agree as follows:

      (1) Tonga  represents and warrants to the Company that Tonga is the record
and  beneficial  owner of 136,411  shares of the Company's  Series B Convertible
Preferred Stock (the "Securities").

      (2) Tonga agrees to sell the  Securities  to the Company,  and the Company
agrees to  purchase  such  securities  for  $210,000  and  warrants  in the form
attached as Annex I hereto to purchase  15,000  shares of the  Company's  Common
Stock (the "Purchase Price").

      (3) Within three business days of the date of this Agreement,  Tonga shall
deliver to the Company by federal  express at its address set forth in Section 6
below certificates  representing the Securities,  duly endorsed for transfer and
free and clear of all Liens (as  defined  below).  Within two  business  days of
receipt of such  Securities  duly  endorsed,  the Company shall deposit the cash
portion of the Purchase  Price and the executed  warrants in federal  express to
the address set forth in Section 6 below.

      (4) Tonga  represents  and warrants to the Company,  and by delivering the
Securities  to the  Company  at the  closing  shall be deemed to  represent  and
warrant to the Company as of the closing date, that:

           (a) Tonga has good and valid title to the Securities,  free and clear
of all liens,  encumbrances,  equities,  claims,  proxies or other voting rights
("Liens");  and, upon delivery of such  Securities and the  consummation  of the
sale  pursuant  hereto,  the Company  will  receive good and valid title to such
Securities, free and clear of all Liens.

           (b) All consents, approvals,  authorizations and orders necessary for
the  execution,  delivery and  performance  by Tonga of this Agreement have been
obtained; and Tonga has full right, power and authority to execute,  deliver and
perform this Agreement;  and this Agreement is a valid and binding obligation of
Tonga, enforceable against Tonga in accordance with its terms.

           (c) Upon  receipt of the  Purchase  Price,  Tonga will have no claims
against the Company with respect to the Securities or any converitble debentures
and the  related  agreements,  including  without  limitation,  any claims as to
registration  rights  (including  a claim  that the  Company  has  been  late in
registering  any  securities,  including  common  stock  underlying  convertible
debentures) or any interest or penalties  (whether  related to the Securities or
convertible debentures).

      (5) Each party,  for  itself  and on behalf  of all  direct  and  indirect
partners,  officers,   directors,   employees,   affiliates  (both  persons  and
entities),   representatives,   agents,  representatives,   servants,  trustees,
beneficiaries,  predecessors  in  interest,  successors  in  interest,  assigns,
nominees and insurers (collectively,  the "Releasing Parties"),  shall be deemed
to have  released  and  forever  discharged  the other  party and its  officers,
directors,   employees,   affiliates   (both  persons  and  entities),   agents,
representatives,  servants,  trustees,  beneficiaries,  processors  in interest,


<PAGE>


successors in interest, assigns, nominees and insurer of each such party, of and
from any and all claims, demands,  actions and causes of actions,  whether known
or unknown, fixed or contingent, that any of the Releasing Parties may have had,
may now have or may  hereafter  acquire with  respect to any matters  whatsoever
arising under or in any way related to the purchase and sale of the Company's 6%
convertible  debentures  due  July  21,  2000  and  Series  B  Preferred  Stock.
Notwithstanding anything to the contrary contained herein, the foregoing release
shall  not  release  either  party  from  claims  arising  from a breach of this
agreement or under the warrants delivered as part of the Purchase Price.

           Each of the parties hereto represents, warrants and covenants that it
has not, and at the time this release  becomes  effective  will not have,  sold,
assigned, transferred or otherwise conveyed to any other person or entity all or
any portion of its rights, claims,  demands,  actions or causes of action herein
released.

           Each of the parties  hereto  acknowledge  that its is  familiar  with
Section  1542 of the Civil Code of the State of  California,  which  provides as
follows:

                "A general  release does not extend to claims which the creditor
                does not know or  suspect  to exist in his  favor at the time of
                executing  the  release,   which  if  known  by  him  must  have
                materially affected his settlement with the debtor."

           Each of the  parities  hereto  hereby  waives  any and all rights and
benefits  that it now has or in the future may have  under  Section  1542 of the
Civil Code (and under the comparable provisions of any other applicable law) and
agrees and  acknowledges  that this Agreement  contains a full and final release
applying to unknown and unanticipated claims, injuries or damages arising out of
the subject matter hereof, as well as to those now known or disclosed.

       (6)  Notices.  Each notice  required  hereunder  shall be in writing,  be
delivered by hand, mail, telegram, or facsimile  transmission,  postage prepaid,
and shall be deemed to have been duly given or made when  received  by the party
to which it was sent at its  following  address (or at such other address as may
hereafter be furnished by one party to the other in writing):

To the Company:

US Wireless Data, Inc.
805 Third Avenue - 8th Floor
New York, NY 10022
Attn: Dean Leavitt

To Tonga Partners, L.P.:
c/o Cannell Capital Management
600 California Street
San Francisco, California 94108
Attn: Linda Fung


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<PAGE>


      (7)  Counterparts.  This  Agreement  may  be  executed  in any  number  of
counterparts  with the same effect as if all signing parties had signed the same
document.  All counterparts  shall be construed together and constitute the same
instrument.


      IN WITNESS WHEREOF,  the parties have has signed this Agreement as of this
_______ day of May 2000.



                                               THE CUTTYHUNK FUND LIMITED



                                               By:
                                                  ------------------------------
                                                  Name:
                                                        ------------------------
                                                  Title:
                                                        ------------------------

                                               U.S. WIRELESS DATA, INC.



                                               By:
                                                  ------------------------------
                                                  Name:
                                                        ------------------------
                                                  Title:
                                                        ------------------------







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