EXHIBIT 5.1

                                  April 2, 2002

ABM Industries Incorporated
160 Pacific Avenue, Suite 222
San Francisco, California  94111

      Re:   ABM Industries Incorporated Registration Statement
            on Form S-8/ 2002 Price-Vested Performance Stock Option Plan

Ladies and Gentlemen:

      At your request, we are rendering this opinion in connection with the
proposed issuance pursuant to the ABM Industries Incorporated 2002 Price-Vested
Performance Stock Option Plan (the "Plan"), of up to 2,000,000 shares of common
stock, $0.01 par value ("Common Stock"), of ABM Industries Incorporated, a
Delaware corporation (the "Company").

      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 2,000,000 shares
of Common Stock to be issued by the Company pursuant to the Plan are duly
authorized shares of Common Stock and, when issued in accordance with the
provisions of 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. In giving such consent, we do not consider
that we are an "expert" 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



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