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                                                                   EXHIBIT 10.20


                               THIRD AMENDMENT TO
                                 LOAN AGREEMENT

         This THIRD AMENDMENT TO LOAN AGREEMENT (this "Amendment"), dated as of
September 25, 1999, is made and entered into between BANK ONE, TEXAS, NATIONAL
ASSOCIATION ("Bank"), and MEDICALCONTROL, INC., a Delaware corporation
("Borrower").

                                    RECITALS

         A. Bank and Borrower entered into that certain Loan Agreement, dated
September 25, 1998, and amended on March 31, 1999 and May 14, 1999 (as amended,
the "Loan Agreement").

         B. Bank and Borrower desire to amend the Loan Agreement as herein set
forth.

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

                                    ARTICLE I
                                   Definitions

         Section 1.01. Definitions. Capitalized terms used in this Amendment, to
the extent not otherwise defined herein, shall have the same definitions
assigned to such terms in the Loan Agreement, as amended hereby.

                                   ARTICLE II
                        Amendments to the Loan Agreement

         Section 2.01. Amendment to Paragraph 1, Credit Facilities. From and
after the date hereof, paragraph 1 of the Loan Agreement is deleted in its
entirety and in place thereof shall be a new paragraph 1 which shall read as
follows:

                  "1. CREDIT FACILITIES. Subject to the terms and conditions set
         forth in this Loan Agreement and the other agreements, instruments and
         documents evidencing, securing, governing, guaranteeing and/or
         pertaining to the Loans, as hereinafter defined (collectively, together
         with the Loan Agreement, referred to hereinafter as the "LOAN
         DOCUMENTS"), Bank hereby agrees to lend to Borrower (a) the amount of
         $1,600,000 (the "TERM LOAN") in a single advance on the date hereof,
         and (b) (the "LINE OF CREDIT"), on a revolving basis from time to time
         during the period commencing on the date hereof and continuing through
         the maturity date of the promissory note evidencing this credit
         facility from time to time, such amounts as Borrower may request
         hereunder; provided, however, the total principal amount outstanding at
         any time under the Line of Credit shall not exceed $400,000 (the Line
         of Credit and the Term Loan are collectively referred to herein as the
         "CREDIT FACILITIES"). Subject to the terms and conditions hereof,
         Borrower may borrow, repay and reborrow hereunder. The sums hereafter
         advanced under the Loans shall be used for general working capital
         purposes.


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         All advances under the Credit Facilities shall be collectively called
         the "Loans." Bank reserves the right to require Borrower to give Bank
         not less than one (1) business day's prior notice of each requested
         advance under the Line of Credit, specifying (i) the aggregate amount
         of such requested advance, (ii) the requested date of such advance, and
         (iii) the purpose for such advance, with such advances to be requested
         in a form satisfactory to Bank."

         Section 2.02. Amendment to Paragraph 5, Guarantors. From and after the
date hereof, paragraph 5 of the Loan Agreement is deleted in its entirety and in
place thereof shall be a new paragraph 5 which shall read as follows:

         "5. GUARANTORS. As a condition precedent to the Bank's obligation to
make the Loans to Borrower, Borrower agrees to cause MedicalControl Network
Solutions, Inc., Diversified Group Administrators, Inc., ppoONE.com, inc. f/k/a
PPO Management Solutions, Inc., Medical Control Holdings, Inc., Business Health
Companies, Inc. and Business Health Management, Inc. (whether one or more, the
"GUARANTORS") to each execute and deliver to Bank contemporaneously herewith a
guaranty agreement, in form and substance satisfactory to Bank."

         Section 2.03. Amendment to Paragraph 10 (b). From and after the date
hereof, paragraph 10 (b) of the Loan Agreement is deleted in its entirety and
replaced with a new paragraph 10 (b) which shall read as follows:

         "(b) Net Worth. Borrower shall maintain, at all times, a "net worth" of
not less than $8,500,000. As used herein, the "net worth" of Borrower shall be
equal to Borrower's total assets minus Borrower's total liabilities."

         Section 2.04. Amendment to Paragraph 10 (e). From and after August 1,
1999, paragraph 10 (e) of the Loan Agreement is deleted in its entirety and
replaced with a new paragraph 10 (e) which shall read as follows:

         "(e) Capital Expenditures. Borrower shall not make capital expenditures
in excess of $250,000 in any fiscal year."

                                   ARTICLE III
                                Covenant Waivers

         Section 3.01. Waiver. Bank hereby waives Borrower's failure to comply
with paragraph 10 (b) for the period ending June 30, 1999. Such waiver is
expressly limited as aforesaid and shall not constitute a waiver of Borrower's
compliance with such covenant for any other past or future period or of any
other breach of the Loan Agreement or any other Loan Document.

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                                   ARTICLE IV
                        Consent to Merger or Dissolution

         Section 4.01. Consent to Merger. Borrower has requested that Bank
consent to the dissolution of Business Health Companies, Inc. or the merger of
Business Health Companies, Inc. into either (i) Medical Control Network
Solutions, Inc., or (ii) Business Health Management, Inc. Bank consents to such
dissolution or merger provided, however, that in the event of merger, such
consent is expressly conditioned upon the receipt by Bank of (i) a certificate
of merger evidencing such merger, (ii) a certificate of good standing and
certificate of existence for the merged entity, (iii) the execution and delivery
to Bank by Medical Control Network Solutions, Inc. and Business Health
Management, Inc. of guarantees of the Loans, in form and substance acceptable to
Bank in its sole discretion, (iv) the execution and delivery to Bank by Medical
Control Network Solutions, Inc. and Business Health Management, Inc. of security
agreements granting to Bank a first priority security interest in all of their
assets to secure payment of the Loans, in form and substance acceptable to Bank
in its sole discretion, (v) the execution and delivery to Bank of UCC-1
financing statements by Medical Control Network Solutions, Inc. and Business
Health Management, Inc., (vi) the execution and delivery to Bank of a pledge
agreement granting to Bank a first priority security interest in one hundred
percent (100%) of the issued and outstanding stock of Business Health
Management, Inc. together with stock certificates evidencing such stock and
stock powers executed in blank, all in form and substance acceptable to Bank in
its sole discretion, (vii) receipt by Bank of certified corporate resolutions
authorizing the foregoing, in form and substance acceptable to Bank in its sole
discretion, and (viii) such other documents and agreements as Bank may
reasonably require.

                                    ARTICLE V
                              Conditions Precedent

         Section 5.01. Conditions Precedent. The effectiveness of this Amendment
is subject to the satisfaction of the following conditions precedent, unless
specifically waived in writing by Bank:

                  (a) Borrower shall have executed and delivered to Bank this
         Amendment, and such other Loan Documents as Bank may require.

                  (b) Each Guarantor shall have executed and delivered this
         Amendment.

                  (c) The representations and warranties contained herein and in
         all other Loan Documents shall be true and correct as of the date
         hereof as if made on the date hereof.

                  (d) Except as waived in writing by Bank, no Event of Default
         shall have occurred and be continuing and no event or condition shall
         have occurred

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         that with the giving of notice or lapse of time or both would be an
         Event of Default.

                  (e) All corporate proceedings taken in connection with the
         transactions contemplated by this Amendment and all documents,
         instruments and other legal matters incident thereto shall be
         satisfactory to Bank and its legal counsel in their sole discretion.

                                   ARTICLE VI
                 Ratifications, Representations, and Warranties

         Section 6.01. Ratifications by Borrower . The terms and provisions set
forth in this Amendment shall modify and supersede all inconsistent terms and
provisions set forth in the Loan Agreement and, except as expressly modified and
superseded by this Amendment, the terms and provisions of the Loan Agreement are
ratified and confirmed and shall continue in full force and effect. The Loan
Agreement as amended by this Amendment shall continue to be legal, valid,
binding and enforceable in accordance with its terms.

         Section 6.02. Renewal and Extension of Security Interests and Liens.
Borrower and each Guarantor jointly and severally renews and affirms the liens
and security interests created and granted in the Loan Documents and agrees that
this Amendment shall in no manner affect or impair the liens and security
interests securing the Indebtedness, and that such liens and security interests
shall not in any manner be waived, the purposes of this Amendment being to
modify the Loan Agreement as herein provided, and to carry forward all liens and
security interest securing same, which are acknowledged by Borrower and each
Guarantor to be valid and subsisting.

         Section 6.03. Representations and Warranties. Borrower represents and
warrants to Bank as follows: (i) the execution, delivery and performance of this
Amendment and any and all Loan Documents executed and/or delivered by Borrower
in connection herewith have been authorized by all requisite corporate action on
the part of Borrower and will not violate the articles or bylaws of Borrower or
any agreement to which Borrower is a party; (ii) the representations and
warranties contained in the Loan Agreement as amended hereby and in each of the
other Loan Documents are true and correct on and as of the date hereof as though
made on and as of the date hereof; (iii) except as waived by Bank, no Event of
Default under the Loan Agreement has occurred and is continuing; and (iv)
Borrower is in full compliance with all covenants and agreements contained in
the Loan Agreement, as amended hereby.

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                                   ARTICLE VII
                                  Miscellaneous

         Section 7.01. Survival of Representations and Warranties. All
representations and warranties made in the Loan Agreement or any other Loan
Document including, without limitation, any Loan Documents furnished in
connection with this Amendment, shall survive the execution and delivery of this
Amendment and the other Loan Documents, and no investigation by Bank or any
closing shall affect such representations and warranties or the right of Bank to
rely thereon.

         Section 7.02. Reference to Loan Agreement. Each of the Loan Documents
and the Loan Agreement and any and all other agreements, documents or
instruments now or hereafter executed and delivered pursuant to the terms hereof
or pursuant to the terms of the Loan Agreement as amended hereby, are hereby
amended so that any reference in such Loan Documents to the Loan Agreement shall
mean a reference to the Loan Agreement as amended hereby.

         Section 7.03. Expenses of Bank. Borrower agrees to pay on demand all
reasonable costs and expenses incurred by Bank directly in connection with the
preparation, negotiation and execution of this Amendment and the other Loan
Documents executed pursuant hereto and any and all amendments, modifications,
and supplements thereto, including, without limitation, the costs and fees of
Bank's legal counsel, and all costs and expenses incurred by Bank in connection
with the enforcement or preservation of any rights under the Loan Agreement, as
amended hereby, or any other Loan Documents including, without limitation, the
reasonable costs and fees of Bank's legal counsel.

         Section 7.04. Severability. Any provision of this Amendment held by a
court of competent jurisdiction to be invalid or unenforceable shall not impair
or invalidate the remainder of this Amendment and the effect thereof shall be
confined to the provision so held to be invalid or unenforceable.

         SECTION 7.05. APPLICABLE LAW. THIS AMENDMENT SHALL BE DEEMED TO HAVE
BEEN MADE AND TO BE PERFORMABLE IN AND SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS.

         Section 7.06. Successors and Assigns. This Amendment is binding upon
and shall inure to the benefit of the parties hereto and their respective
successors, assigns, heirs, executors, and legal representatives, except that
none of the parties hereto other than Bank may assign or transfer any of its
rights or obligations hereunder without the prior written consent of Bank.

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         Section 7.07. Counterparts. This Amendment may be executed in one or
more counterparts, each of which when so executed shall be deemed to be an
original, but all of which when taken together shall constitute one and the same
instrument.

         Section 7.08. Effect of Waiver. No consent or waiver, express or
implied, by Bank to or for any breach of or deviation from any covenant,
condition or duty by Borrower, shall be deemed a consent to or waiver of any
other breach of the same or any other covenant, condition or duty.

         Section 7.09. Headings. The headings, captions, and arrangements used
in this Amendment are for convenience only and shall not affect the
interpretation of this Amendment.

         Section 7.10. Conflicting Provisions. If any provision of the Loan
Agreement as amended hereby conflicts with any provision of any other Loan
Document, the provision in the Loan Agreement shall control.

         SECTION 7.11. RELEASE. BORROWER AND EACH GUARANTOR HEREBY ACKNOWLEDGES
THAT NEITHER BORROWER NOR ANY GUARANTOR HAS ANY DEFENSE, COUNTERCLAIM, OFFSET,
CROSS-COMPLAINT, CLAIM OR DEMAND OF ANY KIND OR NATURE WHATSOEVER THAT CAN BE
ASSERTED TO REDUCE OR ELIMINATE ALL OR ANY PART OF BORROWER'S OR ANY GUARANTOR'S
LIABILITY TO REPAY THE INDEBTEDNESS OR TO SEEK AFFIRMATIVE RELIEF OR DAMAGES OF
ANY KIND OR NATURE FROM BANK. BORROWER AND EACH GUARANTOR HEREBY VOLUNTARILY AND
KNOWINGLY RELEASES AND FOREVER DISCHARGES BANK, ITS PREDECESSORS, AGENTS,
EMPLOYEES, SUCCESSORS AND ASSIGNS, FROM ALL POSSIBLE CLAIMS, DEMANDS, ACTIONS,
CAUSES OF ACTION, DAMAGES, COSTS, EXPENSES, AND LIABILITIES WHATSOEVER, KNOWN OR
UNKNOWN, ANTICIPATED OR UNANTICIPATED, SUSPECTED OR UNSUSPECTED, FIXED,
CONTINGENT, OR CONDITIONAL, AT LAW OR IN EQUITY, ORIGINATING IN WHOLE OR IN PART
ON OR BEFORE THE DATE THIS AGREEMENT IS EXECUTED, WHICH BORROWER OR ANY
GUARANTOR MAY NOW OR HEREAFTER HAVE AGAINST BANK, ITS PREDECESSORS, AGENTS,
EMPLOYEES, SUCCESSORS AND ASSIGNS, IF ANY, AND IRRESPECTIVE OR WHETHER ANY SUCH
CLAIMS ARISE OUT OF CONTRACT, TORT, VIOLATION OF LAW OR REGULATIONS, OR
OTHERWISE OR ARISE FROM ANY LOAN, INCLUDING, WITHOUT LIMITATION, ANY CONTRACTING
FOR, CHARGING, TAKING, RESERVING, COLLECTING OR RECEIVING INTEREST IN EXCESS OF
THE HIGHEST LAWFUL RATE, THE EXERCISE OF ANY RIGHTS AND REMEDIES UNDER THE LOAN
DOCUMENTS, AND/OR NEGOTIATION AND EXECUTION OF THIS AMENDMENT.

         SECTION 7.12. ENTIRE AGREEMENT. THIS AMENDMENT, THE LOAN AGREEMENT AND
ALL OTHER LOAN DOCUMENTS EXECUTED AND DELIVERED IN CONNECTION WITH AND PURSUANT
TO THIS AMENDMENT

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AND THE LOAN AGREEMENT REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES AND
MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT
ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN
THE PARTIES.

         EXECUTED as of the date first written above.

                                           Bank One, Texas, National Association


                                           By: /s/ C. DIANNE WOOLEY
                                              ----------------------------------
                                              C. Dianne Wooley, Vice President

                                           MedicalControl, Inc.


                                           By: /s/ J. WARD HUNT
                                              ----------------------------------
                                              J. Ward Hunt, President

                           CONFIRMATION BY GUARANTORS

         Each of the undersigned, MedicalControl Network Solutions, Inc.,
Diversified Group Administrators, Inc., ppoONE.com,inc. (f/k/a PPO Management
Solutions, Inc.), Business Health Companies, Inc. and Medical Control Holdings,
Inc., hereby (i) consents and agrees to the terms hereof and agrees to be bound
by this Amendment, (ii) consents, acknowledges, and agrees to the execution,
delivery, and performance by Borrower of this Amendment, (iii) acknowledges and
agrees that this Amendment does not affect, diminish, waive, or release its
obligations under the Unlimited Guaranty executed by it or under the Security
Agreement executed by it, (iv) ratifies and confirms its obligations pursuant to
such Unlimited Guaranty and such Security Agreement, and (v) covenants,
acknowledges, and agrees that it guaranties the repayment of the Guaranteed
Indebtedness, as provided in such Unlimited Guaranty.

                                          GUARANTORS:

                                          MedicalControl Network Solutions, Inc.


                                          By:     /s/ ROBERT O. BROOKS
                                             -----------------------------------
                                             Robert O. Brooks, President
                                             and Chief Executive Officer


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                                          Diversified Group Administrators, Inc.


                                          By: /s/ J. WARD HUNT
                                             -----------------------------------
                                             J. Ward Hunt,
                                             Chairman of the Board


                                          ppoONE.com, inc. f/k/a PPO Management
                                          Solutions, Inc.


                                          By: /s/ ROBERT O. BROOKS
                                             -----------------------------------
                                             Robert O. Brooks, President
                                             and Chief Executive Officer


                                          Business Health Companies, Inc.


                                          By: /s/ ROBERT O. BROOKS
                                             -----------------------------------
                                             Robert O. Brooks, Executive
                                             Vice President


                                          Medical Control Holdings, Inc.



                                          By: /s/ J. WARD HUNT
                                             -----------------------------------
                                             J. Ward Hunt, President and
                                             Chief Executive Officer
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