Exhibit 5.1

                        [Acuity Brands, Inc. Letterhead]

                                 July 11, 2005

Acuity Brands, Inc.
1170 Peachtree Street, N.E.
Atlanta, Georgia 30309

           Re: Acuity Brands, Inc. Registration Statement on Form S-8

Ladies and Gentlemen:

      I have acted as counsel for Acuity Brands, Inc., a Delaware corporation
(the "Company"), in connection with the preparation of a Registration Statement
on Form S-8 (the "Registration Statement") to be filed with the Securities and
Exchange Commission covering the proposed offer and sale of up to an aggregate
of 8,980,619 shares of the Company's common stock, $0.01 par value (the "Common
Stock"), pursuant to the Company's Long-Term Incentive Plan, as amended and
restated (the "Plan").

      As such counsel, I have reviewed the Plan. I have also examined and relied
upon such records, documents, certificates and other instruments as in my
judgment are necessary or appropriate to form the basis for the opinions
hereinafter set forth. In all such examinations, I have assumed the genuineness
of signatures on original documents and the conformity to such original
documents of all copies submitted to me as certified, conformed or photographic
copies, and as to certificates of public officials, I have assumed the same to
have been properly given and to be accurate.

      The opinions expressed herein are limited in all respects to the General
Corporation Law of the State of Delaware, and no opinion is expressed with
respect to the laws of any other jurisdiction or any effect which such laws may
have on the opinions expressed herein. This opinion is limited to the matters
stated herein, and no opinion is implied or may be inferred beyond the matters
expressly stated herein.

      Based upon the foregoing, it is my opinion that (i) the Plan, and the
issuance of the shares of Common Stock pursuant to the Plan, have been
authorized; and (ii) upon the issuance of the shares of Common Stock in
accordance with the terms and conditions of the Plan, the shares of Common Stock
issued thereunder will be validly issued, fully paid and nonassessable.

      I hereby consent to the filing of this opinion as Exhibit 5.1 to the
Registration Statement.

                                                     Sincerely,

                                                     /s/ Kenyon W. Murphy, Esq.