EXHIBIT 5.1



                           COTTON, BLEDSOE, TIGHE & DAWSON
                              A PROFESSIONAL CORPORATION
                                   ATTORNEYS AT LAW
                                      SUITE 300
                                  500 WEST ILLINOIS
                              MIDLAND, TEXAS  79701-4337
                             P.O. BOX 2776 ZIP 79702-2776
                               TELEPHONE (915) 684-5782
                                  FAX (915) 682-3672

                                  November 20, 1996


Costilla Energy, Inc.
400 West Illinois, Suite 1000
Midland, Texas 79701

    Re:  Registration Statement on Form S-8
         Outside Directors Stock Option Plan of Costilla Energy, Inc.

Gentlemen:

    We have acted as counsel for Costilla Energy, Inc., a Delaware corporation
(the "Company") in connection with the registration under the Securities Act of
1933, as amended (the "Act"), of 50,000 shares (the "Shares") of the common
stock, par value $0.10 per share (the "Common Stock") of the Company reserved
for issuance under the Outside Directors Stock Option Plan of Costilla Energy,
Inc. (the "Plan").  A Registration Statement on Form S-8 (the "Registration
Statement") covering the sale of the Shares was filed under the Act with the
Securities and Exchange Commission (the "Commission").

    In reaching the conclusions expressed in this opinion, we have examined
signed copies of the Registration Statement and all exhibits thereto.  We have
also examined and relied upon originals or copies certified to our satisfaction,
of (i) the Certificate of Incorporation and Bylaws of the Company, (ii) minutes
and records of the corporate proceedings of the Company with respect to the
issuance of the Shares and related matters, (iii) the Plan, and (iv) such other
agreements and instruments relating to the Company as we have deemed necessary
or appropriate 



Costilla Energy, Inc.
November 20, 1996
Page 2

for the purposes of the opinions hereinafter expressed.  In rendering such 
opinions, we have relied, to the extent we deemed reasonable, on certificates 
and certain other information provided to us by officers of the Company and 
public officials as to matters of fact of which the maker of such certificates 
or the person providing such information had knowledge. Furthermore, in 
rendering such opinions we have assumed that the signatures on all documents 
examined by us are genuine, that all documents and corporate record books 
submitted to us as originals are authentic, accurate and complete, and that 
all documents submitted to us as copies are true, correct and complete copies 
of the originals thereof.

    Based solely upon the foregoing, subject to the assumptions, limitations
and qualifications set forth herein, and specifically limited in all respects to
the laws of the State of Texas, of the United States of America and the General
Corporation Law of the State of Delaware, we are of the opinion that the Shares
registered pursuant to the Registration Statement have been duly and validly
authorized by the Company, and when paid for, issued or sold and delivered in
accordance with the terms of the Plan such Shares will be legally issued, fully
paid and nonassessable.  Please note in this regard that we are not licensed to
practice law in the State of Delaware, but we have reviewed Delaware law in
connection with the opinions expressed herein.

    We hereby consent to the use of this opinion as an exhibit to the
Registration Statement. In giving this consent we do not thereby admit that we
come within the category of persons whose consent is required under Section 7 of
the Act or the rules and regulations of the Commission promulgated thereunder.

    This opinion is rendered only to the Company and solely for the benefit of
the Company and the Commission in connection with the registration and the
issuance of the Shares pursuant to the Registration Statement and the Plan,
respectively.  This opinion may not be otherwise used, circulated, quoted,
relied upon, or referred to by you or the Commission for any other purpose or by
any other person, firm or corporation for any purpose, without our prior written
consent.

                                              Yours very truly,

                                       COTTON, BLEDSOE, TIGHE & DAWSON


                                       By:  /s/ Dan G. LeRoy
                                            Dan G. LeRoy