Exhibit 10.46
                            SHARE EXCHANGE AGREEMENT

         This Share Exchange  Agreement  (this  "Agreement") is made and entered
into as of the 31st day of December,  1998, by and between  American  Physicians
Service Group, Inc., a Texas corporation ("APS") and David L.
Berry, M.D., (the "Shareholder").

                                R E C I T A L S:

         WHEREAS,  pursuant to that certain Agreement and Plan of Reorganization
(the "Merger  Agreement")  entered into by Shareholder of even date herewith and
the other  contracts and  agreements to which  Shareholder  was, or was to be, a
party as contemplated in the Merger Agreement (the Merger Agreement and all such
other contracts and agreements are  hereinafter  referred to collectively as the
"Acquisition Documents"), Shareholder has acquired or will acquire 64,642 shares
(the "PM  Shares")  of the  $0.001 par value per share  common  stock of Syntera
HealthCare  Corporation,  a Texas corporation ("Syntera") for a consideration of
$7.70 per PM Share (the "Exchange Value"); and

         WHEREAS,  APS has agreed,  on the terms and  subject to the  conditions
hereof, to exchange certain shares of its $0.10 par value per share common stock
("APS Common") for the PM Shares.

         NOW,  THEREFORE,  in  consideration of the foregoing and other good and
valuable  consideration,  the  receipt  and  sufficiency  of  which  are  hereby
acknowledged, the parties hereto agree as follows:

         1.  CONDITIONS  TO EXCHANGE  RIGHT.  In addition to the other terms and
conditions  contained in this Agreement,  Shareholder  shall only be entitled to
exchange  the PM  Shares  for  shares  of APS  Common  if each of the  following
conditions has been satisfied:


<PAGE>


                  (a) There shall not have been,  on or before  December 1, 2001
(the  "Determination  Date"), any registered public offering of the common stock
of  Syntera,  or any other  transaction  or event  pursuant  to which  shares of
Syntera of the same class as the PM Shares shall have become  publicly traded at
a per share price of greater  than $7.70 (as adjusted  for stock  splits,  stock
dividends, combinations and other recapitalizations); and

                  (b) Shareholder  shall not be, or have been, at any time on or
prior to the date of the  closing  of any  exchange  of stock  pursuant  to this
Agreement (the "Closing Date"),  in breach of, or default under, this Agreement,
any of the  Acquisition  Documents  or any other  contract or agreement to which
Shareholder and Syntera and/or APS are parties,  and Shareholder  shall not have
threatened to breach or default  under this  Agreement,  any of the  Acquisition
Documents or any such other contract or agreement; and

                  (c) At the Closing Date,  Shareholder  has all requisite legal
capacity  and  authority  to engage  in the  transactions  contemplated  by this
Agreement,  is the owner of all the PM Shares, and the PM Shares are free of any
and all liens, claims or encumbrances of any kind whatsoever; and

                  (d) At or before the Closing  Date,  Syntera  shall not be, or
have been,  a party to any  merger,  consolidation  or similar  transaction,  or
agreement with respect  thereto,  pursuant to which Syntera was not or would not
be,  the named  surviving  entity  after  such  merger,  consolidation  or other
transaction.

         2. EXCHANGE  NOTICE.  In the event all of the  conditions  described in
Section 1 are satisfied as of the Determination  Date and Shareholder  elects to
exercise  its  right  to  exchange  its PM  Shares  for  shares  of APS  Common,
Shareholder shall provide written notice thereof (the "Exchange Notice") to APS,
which  Exchange  Notice  must be  received  by APS not later  than the date (the
"Expiration  Date") which is ninety (90) calendar  days after the  Determination
Date.  In the event (i) any of the  conditions  required  for an  exchange to be
permissible,  as described in 

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<PAGE>

Section 1 above,  fail to be satisfied on or prior
to  the  Determination  Date,  or  (ii)  any  of  the  conditions  specified  in
subsections  (b),  (c) and (d) of Section 1 fail to be  satisfied on or prior to
the  Closing  Date,  or (iii) APS  fails to  receive  an  Exchange  Notice  from
Shareholder on or prior to the Expiration  Date;  then, in any such case, all of
Shareholder's  rights under this Agreement shall automatically  terminate and be
of no further force or effect whatsoever.

         3.       SHARE CONVERSION.

                  (a)  Shareholder's  right to exchange its PM Shares  hereunder
shall  apply as to all,  but not less  than  all,  of the PM  Shares  which  are
eligible for exchange as described in this  paragraph (a) of Section 3. Assuming
Shareholder  has complied  with all of the  conditions  allowing for an exchange
pursuant  to this  Agreement,  35,422 of the PM  Shares  shall be  eligible  for
conversion as provided in this Agreement; and the remaining 29,220 PM Shares, or
a portion thereof, will only be eligible for an exchange hereunder in the event,
and only to the extent,  the Clinic (as hereinafter  defined)  achieves  certain
Practice  Accrual  Earnings  (as  hereinafter   defined)  levels  prior  to  the
Determination  Date.  For  purposes of this  Agreement,  the terms  "Clinic" and
"Practice  Accrual  Earnings"  shall have the meanings set forth in that certain
Management  Agreement  which is one of the Acquisition  Documents.  The Practice
Accrual Earnings of Clinic for any twelve (12) consecutive monthly period ending
on or prior to the Determination Date is hereinafter  referred to as the "Clinic
PAE." The parties  acknowledge  and agree that in the event  Clinic PAE does not
exceed  $450,000  during any twelve (12)  consecutive  calendar  monthly  period
ending on or prior to the  Determination  Date, then no portion of the 29,220 PM
Shares  shall be subject to exchange  pursuant to this  Agreement.  In the event
that,  during any twelve (12)  consecutive  calendar monthly period ending on or
prior to the  Determination  Date,  the Clinic PAE  exceeds  $450,000,  then the
percentage of the 29,220 PM Shares which will be eligible for exchange  pursuant
to this Agreement (assuming compliance with all other conditions provided for in
this  Agreement)  will be determined by  multiplying  29,220 by a fraction,  the
numerator of which is the amount by which Clinic PAE exceeds  $400,000  (but not
greater than $100,000 in any event), and the denominator of which is $100,000.

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<PAGE>


         EXAMPLE:  The following is provided  purely by way of example only, and
illustrates  the  calculation  of the number of PM Shares  eligible for exchange
under this Agreement, assuming satisfaction of all other conditions allowing for
an exchange pursuant to this Agreement.
                  Assume Clinic PAE is $475,000 for the 12 months ended December
                  31,  1999,  which is the  largest  twelve  (12) month level of
                  Clinic PAE  achieved  in any  period  ended on or prior to the
                  Determination Date.

                  Total PM  Shares  eligible  for  exchange  hereunder  would be
                  determined as follows:

                  $475,000 - $400,000       x     29,220       =      21,915
                  -------------------
                            $100,000
                                                               +      35,422
                                                                      ------
                                                                      57,337
                                                                      ======

         (b) In the event  Shareholder  has complied with all of the  conditions
allowing  for an exchange  pursuant to this  Agreement,  the closing of any such
exchange (the "Closing") shall occur at the offices of APS in Austin,  Texas, on
such day and at such time as the parties  hereto may mutually  agree upon, or in
the failure to so agree, at 10:00 a.m. Austin,  Texas time on the first business
day that falls thirty (30) days after the later of (i) the  Expiration  Date, or
(ii) if a Lock-Up Period (as hereinafter defined) is imposed pursuant to Section
4 hereof,  the day on which such Lock-Up  Period ends.  The maximum number of PM
Shares which  Shareholder has the right to exchange pursuant to paragraph (a) of
this Section are hereinafter  referred to as the  "Exchangeable PM Shares";  and
the "Gross  Exchange  Value" for purposes of this  Agreement is the gross dollar
amount  determined by  multiplying  the  Exchangeable  PM Shares by the Exchange
Value.  For purposes of determining the number of shares of APS Common which may
be  received  upon  any  exchange,  no  consideration  will be  given  to  stock
dividends,  stock  splits,  reverse stock splits or  recapitalizations  to which
Syntera  or the PM  Shares  are  subject  after  the  date  this  Agreement  was
originally  entered into as first above  written.  At the  Closing,  Shareholder
shall be  entitled  to receive  such  shares of APS Common as is  determined  by


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<PAGE>

dividing the Gross  Exchange  Value by the average of the "bid" and "ask" prices
for APS  Common as quoted by the  National  Association  of  Securities  Dealers
Automated  Quotation System at the close of trading on each of the last five (5)
business days immediately preceding the Closing Date.

         (c) At the Closing,  Shareholder shall tender its share  certificate(s)
for all of the Exchangeable PM Shares, duly endorsed in blank, to APS, and shall
also  provide APS with an  executed  blank stock  power,  in form and  substance
reasonably acceptable to APS, wherein Shareholder represents and warrants to APS
(i) that  Shareholder has all necessary  legal capacity,  power and authority to
engage in the transactions  contemplated  hereby, and (ii) that Shareholder owns
all interests in and to the  Exchangeable PM Shares and that the Exchangeable PM
Shares  are  being  transferred  to APS free and clear of all  liens,  claims or
encumbrances of any kind  whatsoever.  The shares of APS Common that Shareholder
receives in the  exchange are  hereinafter  referred to as the "New APS Shares."
The parties  acknowledge and agree that Shareholder shall receive a whole number
of shares of APS Common only,  and that any fractional  share amounts  resulting
from the foregoing  conversion  calculation  shall be rounded up or down, as the
case  may be,  to the  next  whole  number  of  shares.  APS  shall  be under no
obligation to pay any cash or other amounts with respect to any fractional share
amounts,  or to issue  any  fractional  share  amounts  to  Shareholder.  At the
Closing,  Shareholder  shall either receive a share  certificate for all its New
APS Shares or, if APS' transfer  agent is unable to produce such  certificate by
the Closing  Date,  will receive a copy of a registered  letter sent from APS to
the transfer agent instructing the transfer agent to deliver such certificate in
the name of Shareholder directly to Shareholder or Shareholder's designee.

         4. NEW APS SHARES TRANSFERABILITY. APS will have registered the New APS
Shares with the Securities and Exchange Commission,  and made such other filings
and taken such other steps as necessary,  so that  Shareholder  may  immediately
sell, or otherwise  convey,  the New APS Shares without  restriction  (except as
otherwise  provided  below).  Shareholder  agrees to cooperate  fully and in all
respects  with  APS in  connection  with  any such  registration,  whether  such


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<PAGE>

cooperation  is requested  before or after the  Determination  Date.  Failure of
Shareholder to cooperate fully, including without limitation, promptly providing
complete and accurate information to APS, in connection with the registration of
any APS Common shares,  whether such cooperation and/or information is requested
before or after the Determination  Date or before or after Shareholder  delivers
any Exchange Notice,  shall automatically  terminate  Shareholder's rights under
this Agreement.  Notwithstanding  anything contained herein to the contrary,  in
the  event  that APS is in the  process,  either at the  Closing  Date or at the
Determination Date, of registering and/or selling any of its capital stock in or
pursuant to any underwritten  public  offering,  upon the written request of the
lead underwriter  involved therein,  Shareholder agrees, and shall then agree in
writing in form and substance reasonably acceptable to APS, to not sell, attempt
to sell, or solicit or accept any offers to sell or otherwise convey, any of the
New APS Shares for such period of time (not to exceed one hundred  eighty  (180)
days) as may be requested by such lead underwriter (the "Lock-Up Period").

         5.       MISCELLANEOUS.

                  (a) FEES AND  EXPENSES.  Each party hereto  agrees to bear all
fees and expenses  (including  without  limitation all fees and expenses for its
legal counsel and any accountants or other  professional  advisors)  incurred in
connection with the transactions contemplated hereby.

         (b) GOVERNING LAW AND VENUE.  This Agreement  shall be governed by, and
construed  and  enforced  in  accordance  with,  the laws of the  State of Texas
(except the laws of Texas that would  render  such  choice of law  ineffective).
Venue for any action relating to this Agreement shall be proper only in Texas.

         (c) COUNTERPARTS.  This Agreement may be executed simultaneously in one
or more  counterparts,  each of which  shall be deemed an  original,  and all of
which together shall constitute one and the same instrument.

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<PAGE>


         (d) INUREMENT.  This Agreement shall be binding upon the parties hereto
and their  respective  heirs,  legal  representatives,  successors and permitted
assigns.  No party hereto may assign this  Agreement,  or any of their rights or
obligations hereunder,  without the express prior written consent of all parties
hereto in each instance.

         (e) NOTICES.  Any notices  required or permitted to be given under this
Agreement  shall be given in  writing  and  shall be  deemed  received  (a) when
personally  delivered to the relevant party at its address as set forth below or
(b) if sent by mail, on the third day  following the date when  deposited in the
United  States  mail,  certified or  registered  mail,  postage  pre-paid to the
relevant party at its address indicated below:

                  APS:               American Physicians Service Group, Inc.
                                     1301 Capital of Texas Highway, Suite C-300
                                     Austin, Texas 78746-6550
                                     Attn: President

                  Shareholder:       David L. Berry, M.D.
                                     1111 West 34th Street, Suite 301
                                     Austin, Texas 78705


Any party may change its address for purposes of this Agreement by proper notice
to the other party.

                            [Signature page follows]

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<PAGE>



         IN WITNESS  WHEREOF,  the parties hereto have executed this  Agreement,
intending to be legally bound hereby, as of the date first above written.

APS:                                    AMERICAN PHYSICIANS SERVICE GROUP, INC.

                                        By:           /s/ William H Hayes       
                                                      --------------------
                                        Printed Name:     William H Hayes       
                                                      --------------------
                                        Title:            Sr VP Finance         
                                                      --------------------
SHAREHOLDER:

                                                      /s/ David L. Berry, M.D.
                                                      ------------------------



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