Exhibit 5

                          [Bingham Dana LLP Letterhead]

                                November 5, 1999


LeukoSite, Inc.
215 First Street
Cambridge, Massachusetts 02142

Dear Sir or Madam:

         We have acted as counsel for LeukoSite, Inc., a Delaware corporation
(the "Company"), in connection with the Company's Registration Statement on
Form S-8 to be filed with the Securities and Exchange Commission on November
8, 1999 (the "Registration Statement").

         The Registration Statement covers the registration of an additional
450,000 shares of common stock, $.01 par value per share, of the Company (the
"Shares), which are to be issued by the Company upon exercise of employee
stock options to be issued pursuant to the LeukoSite, Inc., Amended and
Restated 1993 Stock Option Plan, as amended (the "Plan").

         We have reviewed the corporate proceedings of the Company with
respect to the authorization of the Plan and the issuance of the Shares
thereunder. We have also examined and relied upon originals or copies,
certified or otherwise identified or authenticated to our satisfaction, of
such agreements, instruments, corporate records, certificates, and other
documents as we have deemed necessary or appropriate as a basis for the
opinions hereinafter expressed. In our examination, we have assumed the
genuineness of all signatures, the conformity to the originals of all
documents reviewed by us as copies, the authenticity and completeness of all
original documents reviewed by us in original or copy form, and the legal
competence of each individual executing any document.

         We further assume that all Shares issued upon exercise of options
granted or to be granted pursuant to the Plan will be issued in accordance
with the terms of such Plan and that the purchase price of the Shares will be
greater than or equal to the par value per share of the Shares.

         Subject to the limitations set forth below, we have made such
examination of law as we have deemed necessary for the purposes of this
opinion. This opinion is limited solely to the Delaware General Corporation
Law as applied by courts located in Delaware.

         Based upon and subject to the foregoing, we are of the opinion that
the Shares, when issued and delivered upon the exercise of options duly
granted pursuant to the Plan and



against the payment of the purchase price therefor, will be validly issued,
fully paid, and non-assessable.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                                         Very truly yours,

                                                         /s/ Bingham Dana LLP

                                                         BINGHAM DANA LLP