NOTE

$12,900,000.00              Dallas, Texas                       January 31, 2000


         FOR VALUE RECEIVED,  the undersigned,  PRIME MEDICAL SERVICES,  INC., a
Delaware corporation ("Maker"), hereby promises to pay to the order of BANK ONE,
TEXAS,  N.A.   ("Payee"),   at  the  offices  of  Bank  of  America,   N.A.,  as
Administrative  Agent (together with any successor as provided in the Agreement,
hereinbelow  defined,  the "Administrative  Agent") at 901 Main Street,  Dallas,
Texas 75202, on April 21, 2003, in lawful money of the United States of America,
the principal  sum of TWELVE  MILLION NINE HUNDERD  THOUSAND AND NO/100  DOLLARS
($12,900,000.00),  or so  much  thereof  as  may  be  advanced  and  outstanding
hereunder  together with the interest on the outstanding  principal balance from
day to day remaining, as herein specified.

         This Note has been  executed  and  delivered  by Maker  pursuant to the
terms of that certain  Fourth  Amended and Restated Loan  Agreement of even date
herewith among Maker,  Payee, the  Administrative  Agent,  BankBoston,  N.A., as
Documentation  Agent,  and each of the other  Lenders  which is or may  become a
party thereto or any successor or assignee  thereof (as the same may be amended,
supplemented or modified from time to time, the  "Agreement")  and is one of the
Notes described therein. Capitalized terms used and not otherwise defined herein
shall have the same meanings as set forth in the Agreement.

         Reference is hereby made to the Agreement for provisions affecting this
Note, including, without limitation,  provisions regarding payments, prepayments
(optional and mandatory),  Events of Default and the Administrative  Agent's and
Payee's right as a result of the occurrence thereof.

         The outstanding  principal  balance hereof shall bear interest prior to
maturity at a varying rate per annum which shall from day to day be equal to the
lesser of (a) the Maximum Rate, or (b) the Applicable Rate in effect from day to
day,  each  such  change in the rate of  interest  charged  hereunder  to become
effective,  without notice to Maker, on the effective date of each change in the
Applicable Rate or the Maximum Rate, as the case may be; provided,  however,  if
at any time the Applicable  Rate shall exceed the Maximum Rate,  thereby causing
the interest rate hereon to be limited to the Maximum Rate,  then any subsequent
reduction in the  Applicable  Rate shall not reduce the rate of interest  hereon
below the Maximum Rate until the total amount of interest  accrued hereon equals
the amount of interest which would have accrued  hereon if the  Applicable  Rate
had at all times been in effect.  Accrued and unpaid interest on this Note shall
be due and  payable  on each  Payment  Date  and on the  Termination  Date.  All
past-due principal and interest shall bear interest as the Default Rate.


<PAGE>





                                        3


         Regardless of any  provision  contained in any Loan  Document,  neither
Administrative  Agent nor any Lender  shall ever be entitled  to  contract  for,
charge, take, reserve,  receive, or apply, as interest on all or any part of the
Obligations,  any amount in excess of the Maximum Rate,  and, if Lenders ever do
so, then such  excess  shall be deemed a partial  prepayment  of  principal  and
treated  hereunder as such and any remaining  excess shall be refunded to Maker.
In determining if the interest paid or payable  exceeds the Maximum Rate,  Maker
and Lenders shall,  to the maximum extent  permitted  under  applicable Law, (a)
treat all  Advances as but a single  extension  of credit (and Lenders and Maker
agree that such is the case and that provision  herein for multiple  Advances is
for convenience only), (b) characterize any nonprincipal  payment as an expense,
fee, or premium rather than as interest,  (c) exclude voluntary  prepayments and
the effects thereof, and (d) amortize,  prorate,  allocate, and spread the total
amount of interest  throughout the entire  contemplated term of the Obligations.
However,  if the  Obligations are paid and performed in full prior to the end of
the full contemplated term thereof,  and if the interest received for the actual
period of existence  thereof  exceeds the Maximum  Amount,  Lenders shall refund
such excess,  and, in such event,  Lenders shall not, to the extent permitted by
Law,  be subject to any  penalties  provided  by any laws for  contracting  for,
charging,  taking,  reserving,  or  receiving  interest in excess of the Maximum
Amount.  The "Maximum Rate" or the "Maximum  Amount," mean the "weekly  ceiling"
from time to time in effect under Texas Finance Code ss. 303.305, as amended.

         Upon the occurrence of an Event of Default,  the  Administrative  Agent
may (and if directed by the Required  Lenders,  shall) declare the entire unpaid
principal  of and  accrued  interest  on this Note  immediately  due and payable
without notice, demand or presentment,  all of which are hereby waived, and upon
such  declaration,  the same  shall  become  and  shall be  immediately  due and
payable,  and the  Administrative  Agent  shall have the right to  foreclose  or
otherwise  enforce all Liens or security  interests  securing payment hereof, or
any part  hereof,  and  offset  against  this  Note any sum or sums  owed by the
Administrative  Agent,  Payee or the  holder  hereof  to Maker.  Failure  of the
Administrative  Agent,  Payee or the holder hereof to exercise this option shall
not constitute a waiver of the right to exercise the same upon the occurrence of
a subsequent Event of Default.

         If the  Administrative  Agent,  Payee or the holder hereof  expends any
effort in any attempt to enforce  payment of all or any part or  installment  of
any sum due the holder  hereunder,  or if this Note is placed in the hands of an
attorney for collection,  or if it is collected  through any legal  proceedings,
Maker agrees to pay all costs, expenses, and fees incurred by the Administrative
Agent, or the holder, including reasonable attorneys' fees.

         This Note shall be governed by and  construed  in  accordance  with the
laws of the  State of Texas  and the  applicable  laws of the  United  States of
America.

         Except as provided in the Agreement,  Maker and each surety, guarantor,
endorser,  and other party ever liable for payment of any sums of money  payable
on this Note  jointly  and  severally  waive  notice,  presentment,  demand  for
payment,  protest,  notice of protest and  non-payment  or  dishonor,  notice of
acceleration,  notice  of  intent to  accelerate,  notice  of intent to  demand,
diligence in  collecting,  grace,  and all other  formalities  of any kind,  and
consent to all  extensions  without notice for any period or periods of time and
partial payments, before or after maturity, and any impairment of any Collateral
securing this Note, all without prejudice to the Administrative  Agent, Payee or
the holder. The Administrative  Agent, Payee and the holder shall similarly have
the  right to deal in any way,  at any time,  with one or more of the  foregoing
parties  without  notice to any  other  party,  and to grant any such  party any
extensions  of time for  payment of any of said  indebtedness,  or to release or
substitute  part or all of the  Collateral  securing  this Note, or to grant any
other indulgences or forbearances whatsoever,  without notice to any other party
and without in any way affecting the personal liability of any party hereunder.


<PAGE>


         Maker hereby authorizes the Administrative  Agent, Payee and the holder
hereof to  endorse on the  Schedule  attached  to this Note or any  continuation
thereof  or to record  in their  internal  records  all  Advances  made to Maker
hereunder  and all  payments  made on account of the  principal  thereof,  which
endorsements  or recordings  shall be prima facie evidence as to the outstanding
principal  amount  of  this  Note;   provided,   however,  any  failure  by  the
Administrative Agent, Payee or the holder hereof to make any such endorsement or
recording shall not limit or otherwise affect the obligations of Maker under the
Agreement or this Note.

         This Note,  together with all the other Notes issued on the date hereof
are given in renewal, amendment, and restatement, but not extinguishment, of the
Revolving  Credit  Notes  issued  under  the Third  Amended  and  Restated  Loan
Agreement,  dated as of April  20,  1998,  among  Maker,  Administrative  Agent,
BankBoston,  N.A., as  Documentation  Agent, and each of the other lenders party
thereto, which were given in renewal, amendment,  increase, and restatement, but
not extinguishment of the Revolving Credit Notes issued under the Second Amended
and Restated Loan Agreement dated as of March 31, 1997 among Maker,  NationsBank
as predecessor  Documentation Agent, BankBoston,  as predecessor  Administrative
Agent, and each of the other lenders party thereto, which were given in renewal,
amendment,  increase, and restatement, but not extinguishment,  of the Revolving
Credit Notes issued under the Amended and Restated  Loan  Agreement  dated as of
April 26, 1996 among Maker,  NationsBank  as  predecessor  Documentation  Agent,
BankBoston,  as predecessor  Administrative Agent, and each of the lenders party
thereto, which were given in renewal, amendment,  increase, and restatement, but
not extinguishment of the Revolving Credit Notes issued under the Loan Agreement
dated  as  of  November  28,  1994  among  Maker,  BankBoston,   as  predecessor
Administrative Agent and the banks named therein.

                                              PRIME MEDICAL SERVICES, INC.



                                                  By: /s/ Teena E. Belcik
                                                      Teena E. Belcik
                                                      Vice President-Treasurer