February 7, 2001







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

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

         Re: $ 400 Million Aggregate Principal Amount of Debt Securities

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 (the
"Registration Statement") under the Securities Act of 1933, as amended (the
"Act") and the proposed issuance of $400 million aggregate principal amount of
6.680% Notes due February 15, 2011 (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 proposed
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") providing for the guarantee (the "Guarantee").

     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 Registration
     Statement,  including the prospectus  dated February 7, 2001 forming a part
     thereof (the "Prospectus"), 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  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  related  to or  affecting  creditors'  rights and to general
     principles of equity.

          (b) The Guarantee has been duly  authorized and, upon execution of the
     Guarantee in accordance with the Guarantee  Agreement and attachment to the
     Securities,  will be legally  issued and a valid and binding  obligation of
     the  Guarantor  entitled to the  benefits of the  Guarantee  Agreement  and
     enforceable  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, and the federal laws of
the United States of America.

     We hereby consent to the  incorporation  by reference of this opinion as an
exhibit to the Registration Statement and to the reference of our firm under the
caption "Legal Matters" in the  Registration  Statement and related  Prospectus.
Our consent to such  reference  does not constitute a consent under Section 7 of
the Act, as 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
                                       ----------------------------------