[Cooper Cameron Corporation Letterhead]

                                                                     Exhibit 5.1

                                  June 12, 2003

Cooper Cameron Corporation
1333 West Loop South, Suite 1700
Houston, TX 77027

Gentlemen:

     I am the General Counsel for Cooper Cameron Corporation, a Delaware
corporation (the "Company"), and have acted in such capacity in connection with
the approval by the Board of Directors of the Company of the Cooper Cameron
Corporation Compensation Deferral Plan, as amended, the Cooper Cameron
Corporation Supplemental Excess Defined Contribution Plan, as amended, and the
2003 Cooper Cameron Corporation Supplemental Excess Defined Contribution Plan
(the "Plans"), and the registration by the Company under the Securities Act of
1933, as amended, (the "Securities Act") of the Deferred Compensation
Obligations and the Supplemental Excess Defined Contribution Obligations of the
Company under the Plan (the "Obligations").

     In connection therewith, I have examined originals or copies certified or
otherwise identified to my satisfaction of the (i) Amended and Restated
Certificate of Incorporation of the Company, (ii) the Second Amended and
Restated By-laws of the Company, (iii) the Registration Statement on Form S-8 to
be filed herewith with the Securities and Exchange Commission (the "SEC") under
the Securities Act (together with all exhibits thereto), (iv) the Plans; (v) the
Trust Agreement with Wachovia Bank and (vi) certain resolutions of the Board of
Directors of the Company relating to the Plans, the Trust Agreement and the
Obligations. I have also examined certificates of public officials, statutes and
such other documents and instruments as I have deemed necessary or appropriate
for the expression of the opinions contained herein.

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

     Based upon the foregoing, and having a regard for such legal considerations
     as I have deemed relevant, I am of the opinion that (i) the Company has
     been duly incorporated and is validly existing in good standing under the
     laws of the State of Delaware, (ii) the Plans and the Trust Agreement have
     been duly and validly approved by the Company, and (iii) the Deferred
     Compensation Obligations and the Supplemental Excess Defined Contribution
     Obligations have been duly and validly authorized by the Company.



Cooper Cameron Corporation
June 12, 2003
Page 2

     I hereby consent to the filing of this opinion as Exhibit 5.1 to the
Registration Statement.

                                                 Very truly yours,


                                                 /s/ William C. Lemmer
                                                 -------------------------------
                                                 William C. Lemmer
                                                 Vice President, General Counsel
                                                    and Secretary