EXHIBIT 5.1



                                 April 10, 1997
Boston Scientific Corporation
One Boston Scientific Place
Natick, MA 01760-1537

RE:                   Target Therapeutics, Inc.
                      1988 Stock Option Plan, As Amended
                      1991 Director Option Plan, As Amended

Gentlemen:

                  This opinion is furnished in connection with the registration,
pursuant to a  Registration  Statement on Form S-8 under the  Securities  Act of
1933,  as  amended  (the  Act),  to be filed with the  Securities  and  Exchange
Commission on or about April 10, 1997 (the Registration Statement), of 2,016,000
shares (the  Shares) of the Common  Stock,  par value $.01 per share (the Common
Stock), of Boston Scientific Corporation,  a Delaware corporation (the Company),
which have been or will be issued pursuant to the Target Therapeutics, Inc. 1988
Stock Option Plan, as amended and 1991 Director Option Plan, as amended, (each a
Plan and  collectively  the Plans)  which were  assumed by the Company  upon the
merger of a subsidiary of the Company with Target Therapeutics, Inc.

                  I have acted as  assistant  general  counsel to the Company in
connection with the foregoing  registration of the Shares.  I or attorneys in my
office have  examined  and relied upon the  originals  or copies,  certified  or
otherwise  identified  to  our  satisfaction,   of  such  records,  instruments,
certificates,  memoranda  and other  documents  as we have deemed  necessary  or
advisable  for purposes of this opinion and have  assumed,  without  independent
inquiry, the accuracy of those documents.  In that examination,  we have assumed
the  genuineness  of all  signatures,  the  conformity  to the  originals of all
documents  reviewed  by  me  or  by  attorneys  in  my  office  as  copies,  the
authenticity  and  completeness of all original  documents  reviewed by me or by
attorneys in my office in original or copy form and the legal competence of each
individual executing such documents. I have further assumed that all options and
shares  granted or to be granted  pursuant  to the Plans were or will be validly
granted in accordance  with the terms of the respective Plan and that all Shares
to be issued upon  exercise of such  options will be issued in  accordance  with
such options and the respective Plan.

                  Based upon the foregoing,  I am of the opinion that,  upon the
issuance and delivery of the Shares in accordance with the terms of such options
and the respective  Plans, and as described in the Registration  Statement,  the
Shares  will be  legally  issued,  fully paid and  non-assessable  shares of the
Company's Common Stock.

                  This  opinion  is  limited  solely  to  the  Delaware  General
Corporation Law.

                  I  consent  to the  filing  of a copy  of this  opinion  as an
exhibit to the Registration Statement.


                                    Very truly yours,



                                    Lawrence J. Knopf
                                    Vice President and Assistant General Counsel