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                                                                    EXHIBIT 5.1


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




December 26, 2000



UTI Energy Corp.
16800 Greenspoint Park, Suite 225N
Houston, TX 77060

Gentlemen:

         We have acted as counsel for UTI Energy Corp., a Delaware corporation
(the "Company"), in connection with the registration under the Securities Act of
1933, as amended, of 72,528 shares (the "Shares") of the Company's common stock,
$.001 par value (the "Common Stock") to be offered by certain shareholders of
the Company.

         In connection therewith, we have examined the Company's Registration
Statement on Form S-3 covering the Shares and the preferred stock purchase
rights which trade with the Shares (the "Registration Statement") filed with the
Securities and Exchange Commission, originals or copies certified or otherwise
identified to our satisfaction of the Restated Certificate of Incorporation of
the Company, the By-laws of the Company, as amended, the corporate proceedings
with respect to the offering of the Shares and the preferred stock purchase
right and such other documents and instruments as we have deemed necessary or
appropriate for the expression of the opinions 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 and the
preferred stock purchase rights related to the Shares, have been duly and
validly authorized, and the Shares have been duly and validly issued and are
outstanding and fully paid and nonassessable.


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         The opinions expressed herein relate solely to, are based solely upon
and are limited exclusively to the General Corporation Law of the State of
Delaware and the federal laws of the United States of America, to the extent
applicable.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the use of our name under the caption "Legal
Matters" in the Prospectus included as part of the Registration Statement.

                                                     Very truly yours,


                                                     Fulbright & Jaworski L.L.P.