Exhibit 99.6

                       AMENDMENT NO. 3 TO RIGHTS AGREEMENT

          This AMENDMENT NO. 3 made as of the 12 day of March, 2003, between
Boston Life Sciences, Inc., a Delaware corporation (the "Company"), and
Continental Stock Transfer & Trust Company, a Delaware corporation
("Continental"), as Rights Agent under that certain Rights Agreement between the
Company and Continental, dated as of September 11, 2001, as amended by Amendment
No. 1 thereto dated as of November 13, 2001 and Amendment No. 2 thereto dated as
of November 22, 2002 (the "Rights Agreement').

          WHEREAS, on September 11, 2001, the Board of Directors of the Company
authorized the issuance of Rights (as defined in the Rights Agreement) to
purchase, on the terms and subject to the provisions of the Rights Agreement,
one one-thousandth of a share of the Company's Series D Preferred Stock (each, a
"Right");

          WHEREAS, on September 11, 2001, the Board of Directors of the Company
authorized and declared a dividend distribution of one Right for every share of
common stock of the Company outstanding on the Dividend Record Date (as defined
in the Rights Agreement) and authorized the issuance of one Right (subject to
certain adjustments) for each share of common stock of the Company issued
between the Dividend Record Date and the Distribution Date (as defined in the
Rights Agreement);

          WHEREAS, the Distribution Date has not occurred; and

          WHEREAS, pursuant to Section 27 of the Rights Agreement, the Board has
approved an amendment to certain provision of the Rights Agreement as set forth
below;

          NOW, THEREFORE, the Rights Agreement is hereby amended as follows:

     1.   Section 1(x) is amended and restated in its entirety as follows:

               "(x) "Exempt Person" shall mean Ingalls & Snyder, L.L.C., a New
          York limited liability company, Ingalls & Snyder Value Partners, L.P.,
          a New York limited partnership, or Robert L. Gipson, so long as such
          Persons, collectively, together with all Affiliates of such Persons,
          shall have Beneficial Ownership of less than 20% of the shares of
          Common Stock then outstanding; provided that for purposes of
          determining whether any such Persons qualify as an Exempt Person, such
          Persons and their Affiliates shall be deemed not to have Beneficial
          Ownership of any Excluded Securities (as defined below) until such
          date after June 1, 2005, if any, as any such Person or any Affiliate
          of any such Person shall acquire, or be deemed to acquire, Beneficial
          Ownership of shares of Common Stock of the Company in addition to the
          shares of Common Stock of which such Person or Affiliate has
          Beneficial Ownership on the close of business on June 1, 2005. The
          term "Excluded Securities" shall mean:

                    (A) the Company's 10% Convertible Senior Secured Promissory
               Notes, dated July 25, 2002 (in the original aggregate principal
               amount of $4,000,000) and dated December 1, 2002 (in the original
               aggregate principal amount of $143,333), and any additional notes
               which may be issued pursuant thereto in the future (collectively,
               the "Notes"), and any shares of the Company's Common Stock issued
               or issuable upon conversion of the Notes;



                    (B) the Company's Warrant No. BLSI-2002-50 exercisable for
               500,000 shares of the Company's Common Stock and any shares of
               the Company's Common Stock issued or issuable upon exercise
               thereof; and

                    (C) the Company's Warrant No. BLSI - 2002 - 54 exercisable
               for 1,000,000 shares of the Company's Common Stock and any shares
               of the Company's Common Stock issued or issuable upon exercise
               thereof."

     4.   Except as expressly amended herein, all other terms and conditions of
the Rights Agreement shall remain in full force and effect.

     5.   This Amendment No. 3 may be executed in any number of counterparts,
each of which shall be an original and all of which shall constitute one in the
same document.

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     IN WITNESS WHEREOF, the parties hereto have executed this Amendment No. 3
as of the day and year first above written.

                                              BOSTON LIFE SCIENCES, INC.


                                              By: /s/ Robert J. Rosenthal
                                                  ----------------------------
                                                    Name: Robert J. Rosenthal
                                                    Title: President


                                              CONTINENTAL STOCK TRANSFER
                                              & TRUST COMPANY


                                              By:  /s/ Steven Nelson
                                                   ----------------------------
                                                    Name:  Steven Nelson
                                                    Title: Chairman of the Board
                                                           and President