(Letterhead of Cahill Gordon & Reindel)











                                February 20, 2002







Burlington Resources Inc.
5051 Westheimer, Suite 1400
Houston, TX  77056-2124

Burlington Resources Finance Company
c/o Burlington Resources Canada Ltd.
Suite 3700, 250 6th Avenue, S.W.
Calgary, Alberta T2P 3H7
Canada

 Re: $350 Million Aggregate Principal Amount of Senior Debt Securities due 2007

Ladies and Gentlemen:

     We have acted as special U.S. counsel to Burlington Resources Finance
Company (the "Company") and Burlington Resources Inc. (the "Guarantor") in
connection with the filing of a Registration Statement on Form S-3 (Registration
No. 333-61600) (such registration statement, together with each document
incorporated by reference therein, the "Registration Statement") under the
Securities Act of 1933, as amended (the "Act"), and the proposed issuance of
$350 million aggregate principal amount of 5.70% Notes due March 1, 2007 (the
"Securities") of the Company to be issued under the Indenture between the
Company and Citibank, N.A., as Trustee, dated as of February 12, 2001 (the
"Indenture"), as well as the guarantee by the Guarantor under the Guarantee
Agreement by the Guarantor in favor of the holders of the Securities and the
Trustee, dated as of February 12, 2001 (the "Guarantee Agreement").

     We have examined such corporate records, documents, certificates and
instruments as we deemed necessary and appropriate to enable us to render the
opinion expressed below.



                                      -2-


     We advise you that, in our opinion:

          (a) Assuming that the Securities have been duly authorized by the
     Company, when such Securities have been executed and authenticated in
     accordance with the terms of the Indenture and delivered to the purchasers
     thereof against payment thereof in the manner described in the prospectus
     dated June 27, 2001 (the "Prospectus") forming a part of the Registration
     Statement, and the prospectus supplement dated February 20, 2002
     supplementing such Prospectus (the "Prospectus Supplement"), such
     Securities will be legally issued and will constitute valid and binding
     obligations of the Company entitled to the benefits of the Indenture and
     enforceable against the Company in accordance with their terms, except as
     enforcement may be limited by bankruptcy, insolvency, fraudulent conveyance
     or transfer, reorganization or other laws of general applicability related
     to or affecting creditors' rights and to general principles of equity.

          (b) The Guarantee Agreement has been duly authorized, executed and
     delivered by the Guarantor and is a valid and binding obligation of the
     Guarantor, enforceable against the Guarantor in accordance with its terms
     except as enforcement may be limited by bankruptcy, insolvency, fraudulent
     conveyance or transfer, reorganization or other laws of general
     applicability relating to or affecting creditors' rights and to general
     principles of equity.

     In rendering the opinion set forth above, we express no opinion as to the
laws of any jurisdiction other than the General Corporation law of the State of
Delaware, including the applicable provisions of the Delaware Constitution and
the reported judicial decisions interpreting the laws of Delaware, the laws of
the State of New York and the federal laws of the United States of America.

     We hereby consent to the filing of this opinion as an exhibit to the Form
8-K of the Guarantor to be incorporated by reference into the Registration
Statement and to the reference of our firm under the caption "Legal Matters" in
the Registration Statement and related Prospectus and the Prospectus Supplement.
Our consent to such reference does not constitute a consent under Section 7 of
the Act and in consenting to such reference we have not certified any part of
the Registration Statement and do not otherwise come within the categories of
persons whose consent is required under Section 7 or under the rules and
regulations of the Securities and Exchange Commission thereunder.

                                          Very truly yours,

                                          /s/ Cahill Gordon & Reindel