[LETTERHEAD OF BALLARD SPAHR ANDREWS & INGERSOLL APPEARS HERE]

                                  EXHIBIT 5 



                                                       July 26, 1996



Boston Life Sciences, Inc.
33 Newbury Street
Suite 300
Boston, MA  02116

Ladies and Gentlemen:

     We have acted as your counsel in connection with the proposed sale of
common stock and warrants by certain Selling Stockholders named in the
Registration Statement on Form S-3 and filed with the Securities and Exchange
Commission under the Securities Act of 1933, as amended.

     In this connection, we have examined and relied upon such corporate records
and other documents, instruments and certificates and have made such other
investigation as we deemed appropriate as the basis for the opinion set forth
below.

     Based upon the foregoing, we are of the opinion that the shares of common
stock and warrants to be sold by the Selling Stockholders have been duly
authorized and, when duly executed, delivered and paid for, will be duly and
validly issued, fully paid and nonassessable.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to this firm under the caption
"Legal Matters" in the Prospectus forming a part thereof.


                                              Very truly yours,