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                                                                       EXHIBIT 5


                                  May 16, 2001


The Keith Companies, Inc.
2955 Red Hill Avenue
Costa Mesa, CA 92626

Ladies and Gentlemen:

     At your request, we have examined the form of Registration Statement on
Form S-8 (the "Registration Statement") to be filed by The Keith Companies, Inc.
(the "Company") with the Securities and Exchange Commission pursuant to the
Securities Act of 1933, as amended, for the purpose of registering the sale of
shares of Common Stock of the Company upon the exercise of options granted under
the Amended and Restated 1994 Stock Incentive Plan. We are familiar with the
proceedings taken and proposed to be taken in connection with the issuance and
sale of the securities in the manner set forth in the Registration Statement.
Subject to completion of the proceedings contemplated in connection with the
foregoing matters, we are of the opinion that all of the Common Stock to be sold
pursuant to the Registration Statement has been duly authorized and, when issued
and sold in the manner set forth in the Registration Statement will, upon such
issuance and sale, be validly and legally issued, fully paid and nonassessable.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement or any amendment thereto.


                                              Respectfully submitted,

                                              /s/ RUTAN & TUCKER, LLP