EXHIBIT 5.1


MINTZ LEVIN                                                 One Financial Center
                                                                Boston, MA 02111
                                                                    617-542-6000
                                                                617-542-2241 fax
                                                                   www.mintz.com

                                  June 16, 2008

ARIAD Pharmaceuticals, Inc.
26 Landsdowne Street
Cambridge, Massachusetts 02139

Gentlemen:

     We have acted as counsel to ARIAD Pharmaceuticals, Inc., a Delaware
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 500,000
shares (the "Shares") of its common stock, $.001 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 Certificate
of Incorporation, as amended, and Restated By-Laws, 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 the Shares, when sold,
will have been duly and validly issued, fully paid and non-assessable shares of
the Common Stock.

     Our opinion is limited to applicable provisions of the Delaware
Constitution, the General Corporation Laws of the State of Delaware 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.

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