Exhibit 5



               Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

                              One Financial Center
                           Boston, Massachusetts 02111


                                                                617 542 6000
                                                                617 542 2241 FAX



                                          May 13, 2004

Vertex Pharmaceuticals Incorporated
130 Waverly Street
Cambridge, Massachusetts 02139-4242

Ladies and Gentlemen:

We have acted as counsel to Vertex Pharmaceuticals Incorporated, a Massachusetts
corporation (the "Company"), in connection with the preparation and filing with
the Securities and Exchange Commission of a Registration Statement on Form S-8
(the "Registration Statement"), pursuant to which the Company is registering the
issuance under the Securities Act of 1933, as amended, of a total of 1,500,000
shares (the "Shares") of its common stock, $.01 par value per share (the "Common
Stock). This opinion is being rendered in connection with the filing of the
Registration Statement. All capitalized terms used herein and not otherwise
defined shall have the respective meanings given to them in the Registration
Statement.

In connection with this opinion, we have examined the Company's Restated
Articles of Organization and By-Laws, as amended and restated, both as currently
in effect; such other records of the corporate proceedings of the Company and
certificates of the Company's officers as we have deemed relevant; and the
Registration Statement and the exhibits thereto.

In our examination, we have assumed the genuineness of all signatures, the legal
capacity of natural persons, the authenticity of all documents submitted to us
as originals, the conformity to original documents of all documents submitted to
us as certified or photostatic copies and the authenticity of the originals of
such copies.

Based upon the foregoing, we are of the opinion that (i) the Shares have been
duly and validly authorized by the Company and (ii) the Shares, when sold, will
have been duly and validly issued, fully paid and non-assessable shares of the
Common Stock, free of preemptive rights.



                   BOSTON NEW YORK RESTON WASHINGTON NEW HAVEN





MINTZ, LEVIN, COHN, FERRIS, GLOVSKY AND POPEO, P.C.


May 13, 2004
Page 2



Our opinion is limited to the General Corporation Laws of the State of
Massachusetts and the reported judicial decisions interpreting those laws, and
we express no opinion with respect to the laws of any other jurisdiction. No
opinion is expressed herein with respect to the qualification of the Shares
under the securities or blue sky laws of any state or any foreign jurisdiction.

We understand that you wish to file this opinion as an exhibit to the
Registration Statement, and we hereby consent thereto.

                                                Very truly yours,

                                                /s/ Mintz, Levin, Cohn, Ferris,
                                                Glovsky and Popeo, P.C.

                                                Mintz, Levin, Cohn, Ferris,
                                                Glovsky and Popeo, P.C.