EXHIBIT 5.1


                   [LETTERHEAD OF FULBRIGHT & JAWORSKI L.L.P.]


                                  July 24, 2003


Patterson-UTI Energy, Inc.
4510 Lamesa Highway
Snyder, Texas 79549

Ladies and Gentlemen:

              We have acted as counsel for Patterson-UTI Energy, Inc., a
Delaware corporation (the "Company"), in connection with the registration under
the Securities Act of 1933, as amended (the "Act"), of 1,566,204 shares (the
"Shares") of the Company's common stock, $0.01 par value, to be issued upon the
terms and subject to the conditions set forth in the Proxy Statement/Prospectus
contained in the Registration Statement on Form S-4 (the "Registration
Statement") relating thereto filed with the Securities and Exchange Commission
by the Company on July 24, 2003. The Shares are to be issued in connection with
the merger (the "Merger") of TMBR/Sharp Drilling, Inc., a Texas corporation
("TMBR/Sharp"), with and into Patterson-UTI Acquisition, LLC, a Texas limited
liability company and wholly owned subsidiary of the Company (the "Sub"),
pursuant to an Agreement and Plan of Merger, dated as of May 26, 2003 (the
"Merger Agreement"), by and among the Company, the Sub and TMBR/Sharp.

              In connection therewith, we have examined originals or copies
certified or otherwise identified to our satisfaction of the Registration
Statement and exhibits thereto, the Merger Agreement and exhibits and schedules
thereto, the Restated Certificate of Incorporation of the Company, the Amended
and Restated Bylaws of the Company, the corporate proceedings with respect to
the Merger and the proposed issuance of the Shares and such other documents and
instruments as we have deemed necessary or appropriate for the expression of the
opinion contained herein.

              We have assumed the authenticity and completeness of all records,
certificates and other instruments submitted to us as originals, the conformity
to original documents of all records, certificates and other instruments
submitted to us as copies, the authenticity and completeness of the originals of
those records, certificates and other instruments submitted to us as copies and
the correctness of all statements of fact contained in all records, certificates
and other instruments that we have examined.

              Based on the foregoing, and having regard for such legal
considerations as we have deemed relevant, we are of the opinion that the Shares
proposed to be issued by the Company in connection with the Merger have been
duly authorized for issuance and, when issued in accordance with the terms of
the Merger Agreement, will be validly issued, fully paid and nonassessable.




              The opinion expressed herein relates solely to, is based solely
upon and is limited exclusively to the federal laws of the United States of
America and the General Corporation Law of the State of Delaware and the
applicable provisions of the Delaware constitution and reported decisions
concerning such laws, and we are expressing no opinion as to the effect of the
laws of any other jurisdiction.

              We hereby consent to the filing of this opinion as an exhibit to
the Registration Statement and to the statements made with respect to us under
the caption "Legal Matters" in the Proxy Statement/Prospectus included as part
of the Registration Statement.


                                             Very truly yours,

                                             /s/ Fulbright & Jaworski L.L.P.

                                             Fulbright & Jaworski L.L.P.