PROMISSORY NOTE


Austin, Texas                                                 September 1, 1999



PROMISE TO PAY: For value  received,  the undersigned  Borrower  (whether one or
more) promises to pay to the order of Lender the Principal Amount, together with
interest on the unpaid  balance of such  amount,  in lawful  money of the United
States of America, in accordance with all the terms,  conditions,  and covenants
of this Note and the Loan Documents identified below.

BORROWER:    Prime/BDR Acquisition, L.L.C., a Delaware limited liability company

BORROWER'S ADDRESS FOR NOTICE:        1301 Capital of Texas Highway, Suite C-300
                                      Austin, Texas  78746
                                      Attention: President

LENDER:           Prime Medical Operating, Inc., a Delaware corporation

LENDER'S ADDRESS FOR PAYMENT:        1301 Capital of Texas Highway, Suite C-300,
                                     Austin, Texas 78746
                                     Attention: Chief Financial Officer

PRINCIPAL  AMOUNT:  Ten  Million  Eight  Hundred  Thirty-Five  Thousand  Dollars
                    ($10,835,000)

INTEREST RATE:  Fifteen Percent (15%)

PAYMENT  TERMS:  Interest on the unpaid  balance of this Note is due and payable
quarterly,  beginning September 1, 1999, and continuing  regularly and quarterly
thereafter on or before the first day of March, June, September, and December of
each year, until September 1, 2006 (the "Maturity  Date"),  when the outstanding
principal  balance  and all accrued  interest  shall be due and payable in full.
Interest will be calculated on the unpaid principal  balance.  Each payment will
be  credited  first  to the  accrued  interest  and  then  to the  reduction  of
principal.

LOAN AGREEMENT:  This Note is executed  pursuant to and is governed by the terms
of that certain Loan Agreement dated September 1, 1999, executed by Borrower and
Lender, as amended (collectively, the "Loan Agreement").

1.       INTEREST PROVISIONS:

Rate:  The  principal  balance of this Note from time to time  remaining  unpaid
prior to maturity  shall bear  interest at the  Interest  Rate per annum  stated
above.




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     Maximum Lawful  Interest:  The term "Maximum Lawful Rate" means the maximum
rate of interest and the term "Maximum  Lawful  Amount" means the maximum amount
of interest that is permissible  under  applicable  state or federal law for the
type of loan evidenced by this Note and the other Loan Documents. If the Maximum
Lawful Rate is increased by statute or other  governmental  action subsequent to
the date of this Note,  then the new Maximum  Lawful Rate shall be applicable to
this Note from the  effective  date  thereof,  unless  otherwise  prohibited  by
applicable law.

     Spreading of Interest:  Because of the  possibility  of irregular  periodic
balances of principal or premature payment,  the total interest that will accrue
under this Note  cannot be  determined  in  advance.  Lender  does not intend to
contract for,  charge,  or receive more than the Maximum  Lawful Rate or Maximum
Lawful Amount  permitted by applicable state or federal law, and to prevent such
an occurrence  Lender and Borrower agree that all amounts of interest,  whenever
contracted  for,  charged,  or received by Lender,  with  respect to the loan of
money evidenced by this Note, shall be spread,  prorated,  or allocated over the
full period of time this Note is unpaid,  including the period of any renewal or
extension  of this Note.  If demand  for  payment of this Note is made by Lender
prior to the full stated  term,  the total  amount of interest  contracted  for,
charged,  or received to the time of such demand shall be spread,  prorated,  or
allocated  along with any interest  thereafter  accruing over the full period of
time that this Note thereafter  remains unpaid for the purpose of determining if
such interest exceeds the Maximum Lawful Amount.

     Excess Interest:  At maturity  (whether by acceleration or otherwise) or on
earlier  final  payment of this Note,  Lender shall  compute the total amount of
interest that has been contracted for, charged, or received by Lender or payable
by Borrower under this Note and compare such amount to the Maximum Lawful Amount
that could have been contracted  for,  charged,  or received by Lender.  If such
computation  reflects that the total amount of interest that has been contracted
for,  charged,  or received by Lender or payable by Borrower exceeds the Maximum
Lawful  Amount,  then Lender  shall apply such  excess to the  reduction  of the
principal balance and not to the payment of interest; or if such excess interest
exceeds the unpaid principal balance, such excess shall be refunded to Borrower.
This  provision  concerning  the  crediting or refund of excess  interest  shall
control and take  precedence  over all other  agreements  between  Borrower  and
Lender so that under no circumstances  shall the total interest  contracted for,
charged, or received by Lender exceed the Maximum Lawful Amount.

     Interest After Default:  At Lender's option,  the unpaid principal  balance
shall bear interest after maturity (whether by acceleration or otherwise) at the
"Default Interest Rate." The Default Interest Rate shall be, at Lender's option,
(i) the Maximum  Lawful Rate,  if such  Maximum  Lawful Rate is  established  by
applicable  law; or (ii) the Interest Rate stated on the first page of this Note
plus five (5)  percentage  points,  if no Maximum  Lawful Rate is established by
applicable  law; or (iii) eighteen  percent (18%) per annum; or (iv) such lesser
rate of  interest  as Lender in its sole  discretion  may choose to charge;  but
never more than the Maximum  Lawful Rate or at a rate that would cause the total
interest  contracted for,  charged,  or received by Lender to exceed the Maximum
Lawful Amount.

     Daily  Computation of Interest:  To the extent permitted by applicable law,
Lender at its option will  calculate  the per diem interest rate or amount based
on the actual  number of days in the year (365 or 366, as the case may be),  and
charge that per diem  interest rate or amount each day. In no event shall Lender
compute  the  interest in a manner  that would  cause  Lender to  contract  for,
charge,  or receive  interest  that would exceed the Maximum  Lawful Rate or the
Maximum Lawful Amount

DEFAULT PROVISIONS:

EVENTS OF DEFAULT AND  ACCELERATION  OF MATURITY:  LENDER MAY, AFTER THIRTY (30)
DAYS'  WRITTEN  NOTICE TO BORROWER  AND  BORROWER'S  FAILURE TO CURE WITHIN SUCH
30-DAY  PERIOD  AND  WITHOUT  FURTHER  NOTICE OR DEMAND,  (except  as  otherwise
required  by  statute),  ACCELERATE  THE  MATURITY  OF THIS NOTE AND DECLARE THE
ENTIRE UNPAID PRINCIPAL BALANCE AND ALL ACCRUED INTEREST AT ONCE DUE AND PAYABLE
IF:

     There is default in the payment of any  installment of principal, interest,
or any other sum  required to be paid under the terms of this Note or any of the
Loan Documents; or

     There is a  breach  or  default  (other  than by  Lender  or Prime  Medical
Services,  Inc.)  under this Note or any of the Loan  Documents,  including  any
instrument  securing the payment of this Note or any loan agreement  relating to
the advance of loan proceeds.

WAIVER BY BORROWER: EXCEPT AS PROVIDED IN PARAGRAPH 2(a) HEREOF AND IN ANY OTHER
LOAN  DOCUMENT,  BORROWER  AND ALL OTHER  PARTIES  LIABLE  FOR THIS NOTE  WAIVE,
DEMAND,  NOTICE  OF  INTENT  TO  DEMAND,  PRESENTMENT  FOR  PAYMENT,  NOTICE  OF
NONPAYMENT,  PROTEST,  NOTICE OF PROTEST,  GRACE, NOTICE OF DISHONOR,  NOTICE OF
INTENT TO ACCELERATE MATURITY, NOTICE OF ACCELERATION OF MATURITY, AND DILIGENCE
IN COLLECTION.  EACH MAKER, SURETY,  ENDORSER, AND GUARANTOR OF THIS NOTE WAIVES
AND AGREES TO ONE OR MORE  EXTENSIONS FOR ANY PERIOD OR PERIODS OF TIME, AND ANY
PARTIAL PAYMENTS,  BEFORE OR AFTER MATURITY,  WITHOUT PREJUDICE TO THE HOLDER OF
THIS NOTE. EACH MAKER, SURETY,  ENDORSER, AND GUARANTOR WAIVES NOTICE OF ANY AND
ALL RENEWALS, EXTENSIONS, REARRANGEMENTS, AND MODIFICATIONS OF THIS NOTE.

     Non-Waiver by Lender: Any previous extension of time, forbearance,  failure
to pursue some remedy,  acceptance  of late  payments,  or acceptance of partial
payment by Lender,  before or after  maturity,  does not  constitute a waiver by
Lender of its subsequent  right to strictly  enforce the collection of this Note
according to its terms.

     Other  Remedies  Not  Required:  Lender shall not be required to first file
suit, exhaust all remedies,  or enforce its rights against any security in order
to enforce payment of this Note.

     Joint and Several Liability:  Each Borrower who signs this Note, and all of
the other  parties  liable for the  payment of this  Note,  such as  guarantors,
endorsers,  and sureties,  are jointly and  severally  liable for the payment of
this Note.

     Attorney's  Fees: If Lender requires the services of an attorney to enforce
the payment of this Note or the performance of the other Loan  Documents,  or if
this Note is  collected  through  any  lawsuit,  probate,  bankruptcy,  or other
judicial  proceeding,  Borrower  agrees to pay  Lender  an  amount  equal to its
reasonable  attorney's fees and other collection  costs. This provision shall be
limited by any applicable statutory  restrictions  relating to the collection of
attorney's fees.

3.       MISCELLANEOUS PROVISIONS:

     Subsequent  Holder:  All references to Lender in this Note shall also refer
to any  subsequent  owner  or  holder  of  this  Note by  transfer,  assignment,
endorsement, or otherwise.

     Transfer:  Borrower  acknowledges  and agrees that Lender may transfer this
Note  or  partial   interests  in  the  Note  to  one  or  more  transferees  or
participants,  including without  limitation  transfers  provided for in Section
8.10 of the Loan  Agreement.  Borrower  authorizes  Lender to disseminate to any
such  transferee or  participant or  prospective  transferee or participant  any
information  it has  pertaining to the loan  evidenced by this Note,  including,
without  limitation,  credit  information  on Borrower and any guarantor of this
Note and any of the type of  information  described  in Section 8.10 of the Loan
Agreement.

     Other Parties Liable:  All promises,  waivers,  agreements,  and conditions
applicable  to Borrower  shall  likewise be  applicable  to and binding upon any
other  parties  primarily  or  secondarily  liable for the payment of this Note,
including all guarantors, endorsers, and sureties.

     Successors  and Assigns:  The provisions of this Note shall be binding upon
and  for  the  benefit  of  the  successors,   assigns,  heirs,  executors,  and
administrators of Lender and Borrower.

     No Duty or Special  Relationship:  Borrower acknowledges that Lender has no
duty of good faith to Borrower,  and Borrower  acknowledges  that no  fiduciary,
trust, or other special relationship exists between Lender and Borrower.

     Modifications:  Any  modifications  agreed  to by  Lender  relating  to the
release of liability of any of the parties  primarily or secondarily  liable for
the  payment  of  this  Note,  or  relating  to the  release,  substitution,  or
subordination  of all or part of the  security  for this  Note,  shall in no way
constitute a release of liability  with respect to the other parties or security
not covered by such modification.

     Entire Agreement:  Borrower warrants and represents that the Loan Documents
constitute the entire agreement  between Borrower and Lender with respect to the
loan  evidenced  by this Note and agrees  that no  modification,  amendment,  or
additional  agreement  with  respect  to such loan or the  advancement  of funds
thereunder will be valid and  enforceable  unless made in writing signed by both
Borrower and Lender.

     Borrower's Address for Notice: All notices required to be sent by Lender to
Borrower shall be sent by U.S. Mail, postage prepaid,  to Borrower's Address for
Notice stated on the first page of this Note, until Lender shall receive written
notification from Borrower of a new address for notice.

     Lender's Address for Payment:  All sums payable by Borrower to Lender shall
be paid at Lender's  Address for Payment  stated on the first page of this Note,
or at such other address as Lender shall designate from time to time.

     Business Use:  Borrower warrants and represents to Lender that the proceeds
of this Note will be used solely for business or commercial purposes,  and in no
way will the proceeds be used for personal, family, or household purposes.

     Chapter 15 Not  Applicable:  It is understood  that Chapter 15 of the Texas
Credit Code  relating to certain  revolving  credit loan  accounts and tri-party
accounts is not applicable to this Note.

     APPLICABLE  LAW:  THIS NOTE HAS BEEN  EXECUTED  AND  DELIVERED IN TEXAS AND
SHALL BE CONSTRUED IN ACCORDANCE  WITH THE APPLICABLE LAWS OF THE STATE OF TEXAS
AND THE LAWS OF THE  UNITED  STATES OF AMERICA  APPLICABLE  TO  TRANSACTIONS  IN
TEXAS.

4.       LOAN DOCUMENTS:

This Note.

The Loan Agreement and the Loan Documents as defined therein.

All other  documents  signed in connection  with the Loan  Agreement or the loan
evidenced by this Note, including, without limitation, that certain Contribution
Agreement,  dated  effective  September  1, 1999,  between  and among  Borrower,
Lender,  Prime  Medical  Services,  Inc.,  a  Delaware  corporation,  Prime/BDEC
Acquisition,  L.L.C., a Delaware limited liability  company,  Barnet Dulaney Eye
Center,  P.L.L.C.,  an Arizona  professional  limited liability  company,  LASIK
Investors, L.L.C., a Delaware limited liability company, David D. Dulaney, M.D.,
Ronald W. Barnet,  M.D., and Mark Rosenberg (the  "Contribution  Agreement") and
each  Transaction  Document  (as  such  term  is  defined  in  the  Contribution
Agreement).



                                              [Signature page follows]



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                                EXECUTION PAGE TO
                                 PROMISSORY NOTE


EXECUTED this 1st day of September, 1999.



             BORROWER:

             PRIME/BDR ACQUISITION, L.L.C., a Delaware limited liability company



                                  By: /s/ David D. Dulaney, M.D.

                                  David D. Dulaney, M.D., Manager


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