EXHIBIT 5

                    [LETTERHEAD OF THOMPSON & KNIGHT, P.C.]

                                August 22, 1997


Petroglyph Energy, Inc.
6209 North Highway 61
Hutchinson, Kansas 67502

Dear Sirs and Madams:

     We have acted as counsel for Petroglyph Energy, Inc., a Delaware
corporation (the "Company"), in connection with the preparation of the Company's
Registration Statement on Form S-1, as amended (the "Registration Statement"),
filed with the Securities and Exchange Commission under the Securities Act of
1933, as amended, relating to the proposed offering of 2,333,333 shares (the
"Shares") of the Company's common stock, par value $.01 per share (the "Common
Stock"), together with 350,000 additional shares of Common Stock (the
"Additional Shares") subject to the underwriters' over-allotment option as
described in the Registration Statement.

     We understand that the Shares and any Additional Shares are to be sold
pursuant to the terms of an Underwriting Agreement (the "Underwriting
Agreement") in substantially the form filed as an exhibit to the Registration
Statement.

     In connection with the foregoing, we have examined the originals or copies,
certified or otherwise authenticated to our satisfaction, of the Registration
Statement and such corporate records of the Company, certificates of public
officials and of officers of the Company, and other agreements, instruments and
documents as we have deemed necessary as a basis for the opinions hereinafter
expressed.  Where facts material to the opinions hereinafter expressed were not
independently established by us, we have relied upon the statements of officers
of the Company, where we deemed such reliance appropriate under the
circumstances.

     Based upon the foregoing and in reliance thereon, and subject to the
assumptions and qualifications hereinafter specified, it is our opinion that:

     1.     The Company is a corporation duly incorporated and validly existing
in good standing under the laws of the State of Delaware.

     2.     Upon (a) the taking of action by the Board of Directors of the
Company (or a duly constituted committee thereof) to determine the price at
which the Shares and Additional Shares are to be sold under the Underwriting
Agreement and (b) the sale of the Shares and the Additional Shares in accordance
with the terms of the Underwriting Agreement for the price so determined, the
Shares and any Additional Shares sold by the Company will be duly authorized by
all necessary corporate action on the part of the Company, validly issued, fully
paid and nonassessable.

 
Petroglyph Energy, Inc.
August 22, 1997
Page 2



         We are members of the Bar of the State of Texas only and do not purport
to be experts on the laws of any state or jurisdiction other than the State of
Texas and the United States. Insofar as the opinions expressed herein relate to
matters governed by Delaware law, we have relied solely upon a reading of the
applicable statutes and the corporate records of the Company and certificates of
public officials and officers of the Company referenced above with respect to
the opinions given herein.

         We hereby consent to the filing of this opinion as Exhibit 5 to the
Registration Statement and to the reference to us under the caption "Legal
Matters" in the prospectus forming a part of the Registration Statement. In
giving this consent, we do not thereby admit that we are within the category of
persons whose consent is required under Section 7 of the Securities Act or the
rules or regulations of the Commission thereunder.

                                Respectfully submitted,

                                THOMPSON & KNIGHT,
                                A Professional Corporation



                                By: /s/ Michael L. Bengtson
                                   ---------------------------------------------
                                   Michael L. Bengtson, Attorney