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                                                                     EXHIBIT 5.1


                                    January 20, 1999
Applied Materials, Inc.
3050 Bowers Avenue
Santa Clara, California  95054



               Re: Registration Statement on Form S-8/
                   Applied Materials, Inc. Executive Deferred Compensation Plan


Ladies and Gentlemen:

               At your request, we are rendering this opinion in connection with
the proposed issuance pursuant to the Applied Materials, Inc. Executive Deferred
Compensation Plan (the "Plan") of up to $20,000,000 in aggregate amount of
deferred compensation obligations (the "Obligations") of Applied Materials, Inc.
(the "Company"). The Obligations are unsecured obligations of the Company to pay
deferred compensation in the future in accordance with the terms of the Plan.

               We have examined instruments, documents, and records which we
deemed relevant and necessary for the basis of our opinion hereinafter
expressed. In such examination, we have assumed the following: (a) the
authenticity of original documents and the genuineness of all signatures; (b)
the conformity to the originals of all documents submitted to us as copies; and
(c) the truth, accuracy and completeness of the information, representations and
warranties contained in the records, documents, instruments and certificates we
have reviewed.

               Based on such examination, we are of the opinion that the
$20,000,000 of Obligations to be issued by the Company pursuant to the Plan are
binding obligations of the Company and, when issued and paid for in accordance
with the Plan, will be legally issued, fully paid and nonassessable.

               We hereby consent to the filing of this opinion as an exhibit to
this Registration Statement on Form S-8 and to the use of our name wherever it
appears in said Registration Statement. In giving such consent, we do not
consider that we are "experts" within the meaning of such term as used in the
Securities Act of 1933, as amended, or the rules and regulations of the
Securities and Exchange Commission issued thereunder, with respect to any part
of the Registration Statement, including this opinion as an exhibit or
otherwise.


                                         Very truly yours,

                                         /s/ Orrick, Herrington & Sutcliffe LLP


                                         ORRICK, HERRINGTON & SUTCLIFFE LLP