Exhibit 99(a)


         PetroCorp Incorporated Plans Sale to Unit Corporation

    TULSA, Okla.--(BUSINESS WIRE)--July 1, 2003--PetroCorp
Incorporated (AMEX:PEX) announced today it has entered into a letter
of intent to be acquired by Unit Corporation (NYSE:UNT).
    The transaction would be valued at approximately $190,000,000
comprised of 2 million shares of Unit common stock and the remainder
in cash. The sale price is subject to normal adjustments for
transactions of this type. The transaction is dependent upon the
execution of a definitive agreement and all necessary consents
including PetroCorp shareholder approval. Fully diluted, PetroCorp
will have approximately 13,130,000 shares outstanding.
    "This transaction is the final step in the Company's plan to
return maximum value to our shareholders. We believe the combination
of cash and stock is particularly attractive. This structure returns
the majority of value to our shareholders in cash while allowing them
to participate in a growing energy company - Unit Corporation," stated
Gary Christopher, president and chief executive officer of PetroCorp.
    PetroCorp Incorporated is a Tulsa, Oklahoma based publicly traded
energy company engaged in the exploration, production, acquisition and
enhancement of oil and natural gas reserves in the Mid-Continent and
Gulf Coast regions in the United States. For more information on
PetroCorp, go to www.petrocorp.com.

    Except for the historical information contained herein, the
matters discussed in this press release are forward-looking statements
that involve risks and uncertainties, and actual results could differ
materially from these expectations. Among the factors that could cause
actual results to differ materially are the timing and success of the
company's drilling activities, the volatility of the prices and supply
and demand for oil and gas, the numerous uncertainties inherent in
estimating quantities of oil and gas reserves and actual future
production rates and associated costs, the usual hazards associated
with the oil and gas industry (including blowouts, cratering, pipe
failure, spills, explosions and other unforseen hazards), and
increases in regulatory requirements, as well as other risks described
from time to time in the company's periodic reports filed with the
Securities and Exchange Commission.
    If a definitive agreement is executed relating to this
transaction, PetroCorp Incorporated and Unit Corporation will file a
proxy statement/prospectus and other relevant documents with the SEC
concerning the proposed merger. INVESTORS ARE URGED TO READ THE PROXY
STATEMENT/PROSPECTUS WHEN IT BECOMES AVAILABLE AND ANY OTHER RELEVANT
DOCUMENTS FILED WITH THE SEC BECAUSE THEY WILL CONTAIN IMPORTANT
INFORMATION. You will be able to obtain the documents free of charge
at the Web site maintained by the SEC at www.sec.gov. In addition, you
may obtain documents filed with the SEC by PetroCorp Incorporated free
of charge by requesting them in writing from PetroCorp, Attn: Investor
Relations, P.O. Box 21298, Tulsa, Oklahoma 74121-1298, or by
telephone, (918) 491-4500. Investors should read the proxy
statement/prospectus and related documents carefully when they become
available before making any voting or investment decisions.


    CONTACT: PetroCorp Incorporated, Tulsa
             Steven R. Berlin or Gary R. Christopher, 918/491-4500