Registration No. 333-32595
                                                Filed Pursuant to Rule 424(b)(3)


                            COMFORT SYSTEMS USA, INC.

                        8,000,000 Shares of Common Stock

                   Supplement No. 3 dated December 9, 1998 to
                          Prospectus dated May 5, 1998


SIGNIFICANT ACQUISITION

      A copy of the Company's Current Report on Form 8-K relating to the
acquisition of Shambaugh & Son, Inc. is attached hereto.



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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                             ----------------------


                                    FORM 8-K

                                 CURRENT REPORT

     PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934

       DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): NOVEMBER 15, 1998

                         Commission File Number: 1-13011

                            COMFORT SYSTEMS USA, INC.
             (Exact name of registrant as specified in its charter)


                     DELAWARE                      76-0484996
         (STATE OR OTHER JURISDICTION OF        (I.R.S. EMPLOYER
                 INCORPORATION)               IDENTIFICATION NO.)


                             777 Post Oak Boulevard
                                    Suite 500
                              Houston, Texas 77056
               (Address of Principal Executive offices) (Zip Code)

       Registrant's telephone number, including area code: (713) 830-9600

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ITEM 2.  ACQUISITION OR DISPOSITION OF ASSETS

On November 15, 1998, the Registrant acquired by merger with a wholly owned
subsidiary Shambaugh & Son, Inc. (the "Business Acquired"), which is engaged in
the mechanical contracting business, primarily relating to heating, ventilation,
air conditioning, electrical, plumbing and fire suppression sprinklers. The
consideration for the acquisition consisted of an aggregate of 1,610,889 shares
of the common stock of the Registrant, $29,750,000 in principal amount of
Convertible Subordinated Notes and approximately $58.4 million in cash. The
consideration paid by the Registrant in the acquisitions, the cash portion of
which constituted borrowing under the Company's credit line with Bank One of
Texas, N.A., as agent, was determined through arm's length negotiations between
representatives of the Registrant and the Business Acquired.

Prior to the transactions, the Business Acquired employed vehicles, equipment
and other miscellaneous personal property in the operation of mechanical
contracting businesses, and the Registrant intends that each business will
continue such activities.

ITEM 7.  FINANCIAL STATEMENTS AND EXHIBITS

(A)  FINANCIAL STATEMENTS OF BUSINESSES ACQUIRED

The Registrant believes that it is impractical to provide financial statements
of the Business Acquired on the date of this filing, and will, if required, file
such financial statements when available but not later than sixty (60) days
after the date on which this Current Report on Form 8-K must be filed.

PRO FORMA FINANCIAL INFORMATION

The Registrant believes that it is impractical to provide pro forma financial
information reflecting the Registrant's acquisitions, the Registrant will, if
required, file such financial information when available but not later than
sixty (60) days after the date on which this Current Report on Form 8-K must be
filed.

EXHIBITS


          2.1   Agreement and Plan of Merger dated November 15, 1998, by and
                among the Registrant, Shambaugh & Son, Inc. and Mark Shambaugh.


                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                  COMFORT SYSTEMS USA, INC.


                                  By: /s/ WILLIAM GEORGE
                                          William George, Senior Vice President

Date:  November 25, 1998