UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549



                                 SCHEDULE 13D/A
                    Under the Securities Exchange Act of 1934
                               (Amendment No. 5)*


                          Prime Medical Services, Inc.
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                                (Name of Issuer)

                Shares of Common Stock, par value $0.01 per share
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                         (Title of Class of Securities)

                                   74156C 10 0
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                                 (CUSIP Number)

                                William H. Hayes
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                          1301 Capital of Texas Highway
                                   Suite C-300
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                               Austin, Texas 78746
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                                 (512) 328-0888
(Name, Address and Telephone Number of Person Authorized to Receive Notices and
 Communications)

                                 March 19, 2002
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             (Date of Event which Requires Filing of this Statement)

         If the filing person has previously filed a statement on Schedule 13G
         to report the acquisition which is the subject of this Schedule 13D,
         and is filing this schedule because of 240.13d-1(e), 240.13d-1(f)
         or 240.13d-1(g), check the following box [ ].

         Note:  Schedules  filed in paper format shall include a signed original
         and five copies of the schedule, including all exhibits. See 240.13d-7
         for other parties to whom copies are to be sent.

         *The remainder of this cover page shall be filled out for a reporting
         person's initial filing on this form with respect to the subject class
         of securities, and for any subsequent amendment containing information
         which would alter disclosures provided in a prior cover page.

         The information required on the remainder of this cover page shall not
         be deemed to be "filed" for the purpose of Section 18 of the Securities
         Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of
         that section of the Act but shall be subject to all other provisions of
         the Act (however, see the Notes).






         Potential persons who are to respond to the collection of information
         contained in this form are not required to respond unless the form
         displays a currently valid OMB control number.
         SEC 1746 (2-98)





CUSIP No.         74156C  10  0


         1.       Names of Reporting Persons.
                  I.R.S. Identification Nos. of above persons (entities only).


                  Employer Identification No. 75-1458323
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         2.       Check the Appropriate Box if a Member of a Group
                  (See Instructions)

                  (a)

                  (b)      X
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         3.       SEC Use Only
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         4.       Source of Funds (See Instructions)  WC
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         5.       Check if Disclosure of Legal Proceedings Is Required Pursuant
                  to Items 2(d) or 2(e)
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         6.       Citizenship or Place of Organization        Texas
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Number of Shares    7.     Sole Voting Power  773,803
Beneficially        ------------------------------------------------------------
Owned by Each       8.     Shared Voting Power
Reporting Person    ------------------------------------------------------------
With                9.     Sole Dispositive Power  773,803
                    ------------------------------------------------------------
                    10.    Shared Dispositive Power
------------------- ------------------------------------------------------------
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         11.      Aggregate Amount Beneficially Owned by Each Reporting Person
                  773,803
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         12.      Check if the Aggregate Amount in Row (11) Excludes Certain
                  Shares (See Instructions)
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         13.      Percent of Class Represented by Amount in Row (11)     4.9%
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         14.      Type of Reporting Person (See Instructions)

                  CO








                         AMENDMENT No. 4 to SCHEDULE 13D


         This Amendment No. 5 to Schedule 13D is being filed on behalf of
American  Physicians  Service  Group,  Inc., a Texas  corporation  ("APS") as an
amendment to the initial  statement on Schedule  13D,  relating to shares of the
common  stock,  par value  $0.01 per share  ("Common  Stock")  of Prime  Medical
Services,  Inc.  (the  "Company")  as filed  with the  Securities  and  Exchange
Commission (the  "Commission") on October 20, 1989, (as amended by Amendment No.
1 filed with the Commission on July 29, 1993, and Amendment No. 2 filed with the
Commission on May 19, 1999,  and  Amendment  No. 3 filed with the  Commission on
March 7, 2002,  and Amendment No. 4 filed with the Commission on April 2, 2002).
Unless otherwise indicated, all defined terms used herein shall have the meaning
ascribed to them in the Schedule 13D.


ITEM 4.  PURPOSE OF TRANSACTION


         Section (a) of Item 4 is hereby amended by adding the following to the
end thereof:


         On March 19, 2002, pursuant to an unsolicited offer, APS sold 1,070,000
shares of Common Stock of the Company through SWS Securities,  Inc. a registered
broker/dealer.  The shares were sold at $6.772 per share with gross  proceeds to
the Company totaling $7,246,500. The proceeds will be used for general corporate
purposes.  APS's March 19,  2002,  sale of Common  Stock was not pursuant to any
plan or proposal to divest APS of its remaining holdings of Common Stock.


ITEM 5.  INTEREST IN SECURITIES OF THE ISSUER


         The indicated provisions of Item 5 are amended as follows:


         (a)      APS is the beneficial owner of 773,803 shares of Common Stock,
which  constitutes  approximately  4.9% of the issued and outstanding  shares of
Common Stock. See Exhibit A for shares of the Company  beneficially owned by the
officers and directors of APS.


         (c)      During the past 60 days, APS effected the last transaction
described in Paragraph (a) of Item 4 above.


         (e)      As a result of the last transaction described in Paragraph (a)
of Item 4 above, APS ceased to be a beneficial owner of more than five percent
of the issues and outstanding shares of Common Stock on March 19, 2002.


ITEM 7.  MATERIAL TO BE FILED AS EXHIBITS


         Exhibit A of Item 7 is replaced in its entirety by the following:


Exhibit A -       Description of Executive Officers and Directors of American
                  Physicians Service Group, Inc., (filed herewith).




Signature

         After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

             April 2,  2002
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Date

            /s/ William H. Hayes
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Signature

            William H. Hayes- Senior Vice President- Finance
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Name/Title


         The original statement shall be signed by each person on whose behalf
the  statement is filed or his  authorized  representative.  If the statement is
signed on behalf of a person by his  authorized  representative  (other  than an
executive  officer or general  partner of this filing  person),  evidence of the
representative's  authority to sign on behalf of such person shall be filed with
the  statement;




provided, however, that a power of attorney for this purpose which is already on
file with the  Commission  may be  incorporated  by reference.  The name and any
title of each person who signs the statement  shall be typed or printed  beneath
his signature.


Attention:  Intentional misstatements or omissions of fact constitute Federal
criminal violations (See 18 U.S.C. 1001)