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                                    EXHIBIT 5


                                                              January 22, 1999


Alpha Industries, Inc.
20 Sylvan Road
Woburn, MA  01801


         Re: Alpha Industries, Inc.
             Registration Statement on Form S-8


Gentlemen:

         We are counsel for Alpha Industries, Inc. (the "Company"). We have been
asked to deliver this opinion in connection with the preparation and filing with
the Securities and Exchange Commission under the Securities Act of 1933, as
amended (the "Act"), of a Registration Statement on Form S-8 (this "Registration
Statement") relating to 100,000 shares of the Company's Common Stock, $.25 par
value per share (the "Shares"). This opinion letter, together with Schedule A
attached hereto (this "Opinion Letter"), is being rendered in connection with
the filing of the Registration Statement.

         The 100,000 Shares covered by the Registration Statement are issuable
under the Company's 1997 Non-Qualified Stock Option Plan for Non-Employee
Directors (the "Plan").

         In connection with this Opinion Letter, we have examined and are
familiar with originals or copies, certified or otherwise identified to our
satisfaction, of the following documents (collectively, the "Documents"):

         1.       a certificate from the Secretary of State of the State of
Delaware dated January 21, 1999 as to the legal existence and good standing of
the Company;

         2.       a copy of the Restated Certificate of Incorporation of the
Company, as amended to date, and a certificate of the Secretary that there have
been no further amendments thereto;

         3.       a copy of the By-laws of the Company, as amended to date,
certified by the Secretary of the Company as presently being in effect;

         4.       the corporate minute books or other records of the Company
pertaining to the proceedings of the stockholders and directors of the Company;

         5.       the Plan;


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         6.       a letter from the Company's transfer agent as to the issued
and outstanding shares of the Company's Common Stock, $.25 par value per share;
and

         7.       the Registration Statement.

         We have assumed, for the purposes of our opinion herein, that any
conditions to the issuance of the Shares under the Plan have been or will be
satisfied in full.

         We have, without independent investigation, relied upon the
representations and warranties of the various parties as to matters of objective
fact contained in the Documents.

         In addition, this Firm, in rendering legal opinions, customarily makes
certain assumptions which are described in Schedule A hereto. In the course of
our representation of the Company in connection with the preparation of the
Registration Statement, nothing has come to our attention which causes us to
believe reliance upon any of these assumptions is inappropriate, and, with your
concurrence, the opinions hereafter expressed are based upon those assumptions.
The Enumerated Party referred to in Schedule A is the Company.

         We have not made any independent review or investigation of orders,
judgments, rules or other regulations or decrees by which the Company or any of
its property may be bound, nor have we made any independent investigation as to
the existence of actions, suits, investigations or proceedings, if any, pending
or threatened against the Company.

         With your concurrence, our opinion hereafter expressed is based solely
upon (1) our review of the Documents, (2) discussions with those of our
attorneys who have devoted substantive attention to the preparation of the
Registration Statement, and (3) such review of published sources of law as we
have deemed necessary.

         Our opinions contained herein are limited to the laws of the
Commonwealth of Massachusetts, the General Corporation Law of the State of
Delaware and the Federal law of the United States of America.

         We express no legal opinion upon any matter other than those explicitly
addressed below, and our express opinion therein contained shall not be
interpreted to be an implied opinion upon any other matter.

         Based upon and subject to the foregoing, we are of the opinion that the
Shares have been duly authorized and, when issued and paid for in accordance
with the terms and conditions of the Plan, the Shares will be validly issued,
fully paid, and non-assessable.





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         We hereby consent to the reference to this firm in the Registration
Statement and to the filing of this opinion as Exhibit 5 to the Registration
Statement.


                                   Very truly yours,




                                   BROWN, RUDNICK, FREED & GESMER, P.C.


                                   By: /s/ Steven R. London 
                                       --------------------------------------- 
                                       Steven R. London, a Member




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                                   SCHEDULE A

                         BROWN, RUDNICK, FREED & GESMER
                              STANDARD ASSUMPTIONS


         In rendering legal opinions, Brown, Rudnick, Freed & Gesmer makes
certain customary assumptions described below:

1.       Each natural person executing any of the Documents has sufficient legal
         capacity to enter into such Documents.

2.       Each Document is accurate, complete and authentic, each original is
         authentic, each copy conforms to an authentic original and all
         signatures are genuine.

3.       All official public records are accurate, complete and properly indexed
         and filed.

4.       There has not been any mutual mistake of fact or misunderstanding,
         fraud, duress, or undue influence by or among any of the parties to the
         Documents.

5.       The conduct of the parties to the Documents has complied in the past
         and will comply in the future with any requirement of good faith, fair
         dealing and conscionability.

6.       The Enumerated Party will obtain all permits and governmental approvals
         required in the future and take all actions similarly required relevant
         to its performance of its obligations under the Documents.

7.       All parties to or bound by the Documents will act in accordance with,
         and will refrain from taking any action that is forbidden by, the terms
         and conditions of the Documents.

8.       There are no agreements or understandings among the parties to or bound
         by the Documents, and there is no usage of trade or course of prior
         dealing among such parties, that would define, modify, waive, or
         qualify the terms of any of the Documents.