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                                                               Exhibit 4.13.1


                                AMENDMENT TO THE
            SECOND AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

      THIS AMENDMENT TO THE SECOND AMENDED AND RESTATED REGISTRATION RIGHTS
AGREEMENT (the "Amendment") is made this 26 day of September, 1997, among
AMERICAN PSYCH SYSTEMS, INC., a Delaware corporation ("Company"), APPLEWOOD
ASSOCIATES, L.P., a New York limited partnership ("Applewood"), SENECA VENTURES,
a New York limited partnership ("Seneca"), WOODLAND PARTNERS, a New York general
partnership ("Woodland Partners"), WOODLAND VENTURE FUND, a New York limited
partnership ("Woodland Venture"), NAZEM & COMPANY IV, L.P., a Delaware limited
partnership ("Nazem"), OXFORD HEALTH PLANS, INC., a Delaware corporation
("Oxford") (Applewood, Seneca, Woodland Partners and Woodland Venture are herein
referred to as the "Applewood Investors") (the Applewood Investors, Nazem and
Oxford are herein after referred to as the "Investors") and PRINCIPAL HEALTH
CARE, Inc. an Iowa corporation ("Principal").

      WHEREAS, the Investors are parties to that certain Second Amended and
Restated Registration Rights Agreement dated June 17, 1996 (the "Agreement");

      WHEREAS, Principal and the Company are parties to that certain Stock
Purchase Agreement, of even date herewith (the "Stock Purchase Agreement"),
under which the Company is issuing 2,705,182 shares of its common stock, par
value $.001 per share (the "Common Stock") to Principal and under which
Principal (or its designee) has certain pre-emptive rights to purchase
additional shares of Common Stock in certain events (the shares of Common Stock
issued and issuable under the Stock Purchase Agreement are collectively referred
to herein as the "Shares");

      WHEREAS, as a condition of entering into the Stock Purchase Agreement,
Principal is requiring that the Company provide Principal (or its designees)
with registration rights with respect to the Shares by permitting Principal to
become a party to the Agreement; and

      WHEREAS, the Company and the Investors desire to amend the Agreement to
include the Shares issued and issuable to Principal (or its designees).

      NOW, THEREFORE, in consideration of the foregoing, for the mutual
covenants hereinafter set forth, and for other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, the parties
intending to be legally bound, mutually agree and covenant as follows:

      1.    PRINCIPAL AS A PARTY TO THE AGREEMENT.  Principal shall be deemed
to be an Investor as that term is defined in the Agreement.

      2.    AMENDMENT TO DEFINITION OF REGISTRABLE SECURITY.  The first
sentence of
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the definition of "Registrable Security", as set forth in Section 1.1 (d) of the
Agreement shall be deleted in its entirety and the following shall be inserted
in lieu thereof

            (d) "Registrable Securities" shall mean the shares of Common Stock
(i) issued and issuable to a Holder (A) upon conversion of the Preferred Stock,
(B) upon conversion of the Notes, (C) upon exercise of the Warrants and (ii)
issued and issuable to Principal Health Care, Inc. (or its designees)
("Principal") pursuant to the Stock Purchase Agreement, including, without
limitation, shares of Common Stock issued or issuable upon exercise of
Principal's preemptive rights.

      3.    AMENDMENT TO NOTICE PROVISION.  A new subsection (v) shall be
added to Section 4.1 of the Agreement by inserting the following after
subsection (iv) of Section 4.1:

      (v) if to Principal, 6705 Rockledge Drive, Bethesda, Maryland 20817
Attention: Corporate Counsel,

      4.    EFFECT OF AMENDMENT.  Except to the extent expressly set forth
herein, the provisions hereof do not amend, modify, release or waive any of
the terms or conditions of the Agreement

      5.    COUNTERPARTS.  This Amendment may be executed in multiple
counterparts.

      IN WITNESS WHEREOF, this Amendment has been executed as of the date and
year first above written.

                                    AMERICAN PSYCH SYSTEMS, INC.


                                    By:   /s/ Kenneth A. Kessler
                                          --------------------------------------
                                          Name:  Kenneth A. Kessler
                                          Title: President

APPLEWOOD ASSOCIATES, L.P.          SENECA VENTURES


By:   /s/ Barry Rubenstein          By:   /s/ Barry Rubenstein
      ---------------------------         -------------------------
      Name:  Barry Rubenstein             Name:  Barry Rubenstein
      Title: General Partner              Title: General Partner


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WOODLAND PARTNERS                   WOODLAND VENTURE FUND


By:   /s/ Barry Rubenstein          By:   /s/ Barry Rubenstein
      ---------------------------         -------------------------
      Name:  Barry Rubenstein             Name:  Barry Rubenstein
      Title: General Partner              Title: General Partner


OXFORD HEALTH PLANS, INC.           NAZEM & COMPANY IV, L.P.

                                          By:  Nazem & Associates IV,
                                               L.P.,
                                          Its General Partner

By:   /s/ Jeffrey H. Boyd           By:   /s/ Jeffrey Krauss
      ---------------------------         -------------------------
       Name: Jeffrey H. Boyd                    Name:  Jeffrey Krauss
       Title: Executive Vice President                Title: General Partner


PRINCIPAL HEALTH CARE, INC.


By:
   ----------------------------------

Title:
      -------------------------------


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