AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON AUGUST 23, 2000
                                               REGISTRATION NO. 333-____________

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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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                                    FORM S-8
                             REGISTRATION STATEMENT
                        UNDER THE SECURITIES ACT OF 1933
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                            COMFORT SYSTEMS USA, INC.
             (Exact name of registrant as specified in its charter)

           DELAWARE                                           76-0526487
  (STATE OF JURISDICTION OF                                 (I.R.S. EMPLOYER
INCORPORATION OR ORGANIZATION)                             IDENTIFICATION NO.)

                        777 POST OAK BOULEVARD, SUITE 500
                              HOUSTON, TEXAS 77056
                                 (713) 830-9600
                   (ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE
                   NUMBER, INCLUDING AREA CODE, OF REGISTRANTS
                          PRINCIPAL EXECUTIVE OFFICES)

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                        1998 EMPLOYEE STOCK PURCHASE PLAN

                            (FULL TITLE OF THE PLAN)

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                                WILLIAM F. MURDY
                             CHIEF EXECUTIVE OFFICER
                            COMFORT SYSTEMS USA, INC.
                        777 POST OAK BOULEVARD, SUITE 500
                              HOUSTON, TEXAS 77056
                                 (713) 830-9600
                               FAX: (713) 830-9696
(NAME, ADDRESS, AND TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)

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                                    COPY TO:
                              WILLIAM GEORGE, ESQ.
                                 GENERAL COUNSEL
                            COMFORT SYSTEMS USA, INC.
                        777 POST OAK BOULEVARD, SUITE 500
                              HOUSTON, TEXAS 77056
                                 (713) 830-9600
                               FAX: (713) 830-9696

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                                                   AMOUNT           MAXIMUM             PROPOSED        AMOUNT OF
              TITLE OF                              TO BE        OFFERING PRICE    MAXIMUM AGGREGATE   REGISTRATION
    SECURITIES TO BE REGISTERED                 REGISTERED (1)     PER UNIT (2)       OFFERING PRICE       FEE
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Common Stock (par value $0.01 per share)(1)       600,000            $4.13            $2,478,000         $654.19
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(1) Pursuant to Rule 416(a), this Registration Statement also registers such
    indeterminate number of additional shares of Common Stock issuable in
    connection with stock splits, share dividends or similar transactions.

(2) Estimated pursuant to Rule 457(h) solely for the purpose of calculating the
    registration fee based on the average of the high and low sales prices for
    the Common Stock as reported by the New York Stock Exchange on August 18,
    2000.

EXPLANATION STATEMENT This registration statement is being filed to register additional securities for issuance under the 1998 Employee Stock Purchase Plan pursuant to General Instruction E of Form S-8. The contents of the Registrant's registration statement on Form S-8, file no. 333-38011, and each of the documents incorporated or deemed to be incorporated by reference thereby, are hereby incorporated herein by reference. EXHIBITS 4.1* Amendment to 1998 Employee Stock Purchase Plan 5.1* Opinion of William George, General Counsel, Comfort Systems USA, Inc. 23.1* Consent of Arthur Andersen LLP 23.2* Consent of William George (included in Exhibit 5.1) 24.1* Powers of Attorney (included on the signature page of this Registration Statement) * Filed herewith 2

SIGNATURES In accordance with the requirements of the Securities Act of 1933, as amended, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements of filing on Form S-8 and has duly authorized this Registration Statement to be signed on its behalf by the undersigned, in the City of Houston, State of Texas on August 18, 2000. COMFORT SYSTEMS USA, INC. By:/s/ WILLIAM F. MURDY, William F. Murdy, CHIEF EXECUTIVE OFFICER We, the undersigned directors and officers of Comfort Systems USA, Inc., constitute and appoint William F. Murdy or William George, III , or either of them, our true and lawful attorneys and agents, to do any and all acts and things in our name and on our behalf in our capacities as directors and officers, and to execute any and all instruments for us and in our names in the capacities indicated below, which said attorneys and agents, or either of them, may deem necessary or advisable to enable said corporation to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission, in connection with the filing of this Registration Statement, including specifically without limitation, power and authority to sign for any of us, in our names in the capacities indicated below, any and all amendments hereto; and we do each hereby ratify and confirm all that the said attorneys and agents, or either of them, shall do or cause to be done by virtue hereof. Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed by the following persons in the capacities and on the dates indicated. SIGNATURE TITLE DATE --------- ----- ---- /s/ WILLIAM F. MURDY Chairman of the Board and August 18, 2000 William F. Murdy Chief Executive Officer /s/ J. GORDON BEITTENMILLER Senior Vice President, August 18, 2000 J. Gordon Beittenmiller Chief Financial Officer and Director (principal accounting and financial officer) 3

SIGNATURE TITLE DATE --------- ----- ---- /s/ GARY E. HESS Executive Vice President, August 18, 2000 Gary E. Hess Chief Operating Officer and Director /s/ ALFRED J. GIARDENELLI, JR. Director August 18, 2000 Alfred J. Giardenelli, Jr. /s/ STEVEN S. HARTER Director August 18, 2000 Steven S. Harter /s/ JOHN MERCADANTE, JR. Director August 18, 2000 John Mercadante, Jr. /s/ ROBERT J. POWERS Director August 18, 2000 Robert J. Powers /s/ DIANE D. SANDERS Director August 18, 2000 Diane D. Sanders /s/ MARK P. SHAMBAUGH Director August 18, 2000 Mark P. Shambaugh 4

EXHIBIT INDEX 4.1* Amendment to 1998 Employee Stock Purchase Plan 5.1* Opinion of William George, General Counsel, Comfort Systems USA, Inc. 23.1* Consent of Arthur Andersen LLP 23.2* Consent of William George (included in Exhibit 5.1) 24.1* Powers of Attorney (included on the signature page hereto of this registration statement). * Filed herewith 5

                                                                     EXHIBIT 4.1

                                    AMENDMENT
                                     TO THE
                            COMFORT SYSTEMS USA, INC.
                        1998 EMPLOYEE STOCK PURCHASE PLAN

      This Amendment to the Comfort Systems USA, Inc. (the "Company") 1998
Employee Stock Purchase Plan (the "Amendment") is executed pursuant to Section
8.1 of the Company's 1998 Employee Stock Purchase Plan (the "Plan"). All
capitalized and undefined terms used herein shall have the meanings ascribed to
such terms in the Plan.

      WHEREAS, the Company's Board of Directors (the "Board") is authorized by
Section 8.1 of the Plan to amend the Plan from time to time, subject to any
required stockholder approval of any such amendments; and

      WHEREAS, at a meeting of the Board on March 3, 2000 the Board authorized
an increase in the number of shares authorized for issuance under the Purchase
Plan by 600,000; and

      WHEREAS, at the annual meeting of stockholders held on May 18, 2000, the
Company's stockholders approved the Amendment.

      NOW, THEREFORE, in order to amend Section 4.1 of the Purchase Plan as
authorized by the Board and approved by the stockholders:

      1. The first sentence of Section 4.1 of the Purchase Plan is hereby
revised in its entirety to read as follows:

            "Subjects to the adjustments in Sections 4.2 and 4.3, an aggregate
            of Nine Hundred Thousand (900,000) shares of Common Stock shall be
            available for purchase by Participants pursuant to the provisions of
            the Plan."

      2. Except as amended hereby, the terms and provisions of the Plan shall
remain in full force and effect, and the Plan and this Amendment shall be read,
taken and construed as one and the same instrument.

            IN WITNESS WHEREOF, and as conclusive evidence of the adoption of
the foregoing Amendment to the Plan by the directors of the Company and approval
and adoption thereof by the stockholders of the Company, the Company has caused
this Amendment to be duly executed in its name and behalf by its proper officers
thereunto duly authorized as of the 20th day of May, 2000.

                                    COMFORT SYSTEMS USA, INC.


                                    By:/S/ WILLIAM GEORGE
                                           William George
                                           Senior Vice President
                                                                     EXHIBIT 5.1

                     [COMFORT SYSTEMS USA, INC. LETTERHEAD]

                                August 22, 2000

U.S. Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C. 20549

      Re:   Registration Statement on Form S-8

Ladies and Gentlemen:

      I am General Counsel of Comfort Systems USA, Inc. (the "Company"), and I
have represented the Company in connection with the preparation of a
Registration Statement on Form S-8 of the Company relating to 600,000 shares of
common stock, par value $.01 per share (the "Common Stock"), of the Company
being registered for issuance pursuant to the 1998 Employee Stock Purchase Plan
(the "Plan").

      I have examined the Certificate of Incorporation, as amended, and the
By-laws of the Company, the Plan and such other corporate documents and records
as I have deemed necessary or appropriate in order to render the opinions set
forth below.

      Based upon the foregoing, and subject to the qualification that I am
admitted to the practice of law only in the State of Massachusetts and do not
purport to be expert in the laws of any jurisdiction other than the State of
Massachusetts and the United States, I am of the opinion that:

      1. The shares of Common Stock to be issued under the Plan are duly
authorized.

      2. When the Common Stock is issued and delivered in accordance with and
pursuant to the terms of the Plan, such Common Stock will be validly issued,
fully paid and nonassessable.

      This opinion is given as of the date hereof, and I assume no obligation to
advise you after the date hereof of facts or circumstances that come to my
attention or changes in law that occur which could affect the opinions contained
herein.

      I hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and the reference to me in Item 5.1 of the Registration
Statement.

                                          Very truly yours,


                                          /s/ WILLIAM GEORGE
                                              William George
                                              General Counsel
                                                                    EXHIBIT 23.1

                   CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

      As independent public accountants, we hereby consent to the incorporation
by reference in this registration statement of our report dated February 22,
2000 included in Comfort Systems USA, Inc's Form 10-K for the year ended
December 31, 1999 and to all references to our Firm included in this
registration statement.

ARTHUR ANDERSEN LLP
/s/ ARTHUR ANDERSEN LLP

Houston, Texas
August 21, 2000