Exhibit 5.1

                                 August 4, 2003

American Technology Corporation
13114 Evening Creek Drive South
San Diego, CA 92128


Ladies and Gentlemen:


         You have requested our opinion with respect to certain matters in
connection with the filing by American Technology Corporation, a Delaware
corporation (the "Company"), of a Registration Statement on Form S-3 (the
"Registration Statement") with the Securities and Exchange Commission, including
a related prospectus filed with the Registration Statement (the "Prospectus")
covering the registration of up to 2,272,727 shares of the Company's common
stock, $.00001 par value (the "Common Stock"), on behalf of certain selling
stockholders including: (i) 1,818,180 shares of issued and outstanding Common
Stock (the "Shares"); and (ii) 454,547 shares of the Common Stock (the "Warrant
Shares") issuable upon the exercise of certain issued and outstanding warrants
(the "Warrants"). This opinion is being furnished in accordance with the
requirements of Item 601(b)(5)(i) of Regulation S-K.

         In connection with this opinion, we have examined and relied upon the
Registration Statement, and related Prospectus, the Company's Certificate of
Incorporation, as amended, the Company's Bylaws, the Warrants, the corporate
proceedings taken by the Company in connection with the issuance of the Shares
and the Warrants, and the originals or copies certified to our satisfaction of
such records, documents, certificates, memoranda and other instruments as in our
judgment are necessary or appropriate to enable us to render the opinion
expressed below. We have assumed the genuineness and authenticity of all
documents submitted to us as originals, the conformity to originals of all
documents submitted to us as copies thereof and the due execution and delivery
of all documents where due execution and delivery are a prerequisite to the
effectiveness thereof.

         On the basis of the foregoing, and in reliance thereon, we are of the
opinion that (i) the Shares are validly issued, fully paid and non-assessable;
and (ii) the Warrant Shares, when issued and sold in accordance with the terms
of the Warrants, will be validly issued, fully paid and non-assessable.

         We consent to the reference to our firm under the caption "Legal
Matters" in the Prospectus included in the Registration Statement and to the
filing of this opinion as Exhibit 5 to the Registration Statement.

         This opinion letter is rendered as of the date first written above and
we disclaim any obligation to advise you of facts, circumstances, events or
developments which hereafter may be brought to our attention and which may
alter, affect or modify the opinion expressed herein. Our opinion is expressly
limited to the matters set forth above and we render no opinion, whether by
implication or otherwise, as to any other matters relating to the Company, the
Shares, the Warrants or the Warrant Shares.

                                  Very truly yours,

                                  /s/ Procopio, Cory, Hargreaves & Savitch LLP
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                                  PROCOPIO, CORY, HARGREAVES & SAVITCH LLP