<PAGE>

                                                                EXHIBIT 10.16.4

                      FOURTH AMENDMENT TO CREDIT AGREEMENT

      THIS FOURTH AMENDMENT TO CREDIT AGREEMENT made and entered into as of
September 15, 2000 (this "AMENDMENT"), by and among PSYCH SYSTEMS HOLDINGS,
INC., a Delaware corporation (the "COMPANY"), AMERICAN PSYCH SYSTEMS HOLDINGS,
INC., a Delaware corporation (the "HOLDING COMPANY"), the Lenders signatory
hereto (the "LENDERS"), and BANK OF AMERICA, N.A. (successor in interest to Banc
of America Commercial Finance Corporation, formerly known as NationsCredit
Commercial Corporation), as a Lender and as Agent for the Lenders (the "AGENT").

                               STATEMENT OF FACTS

A.    The Company, the Holding Company, the Lenders and the Agent are parties to
      that certain Credit Agreement, dated as of December 23, 1998, as amended
      by the First Amendment dated August 26, 1999, the Second Amendment dated
      as of October 18, 1999 and the Third Amendment dated as of June 23, 2000
      (as amended, the "CREDIT AGREEMENT"; capitalized terms used in this
      Amendment and not otherwise defined herein have the meanings given in the
      Credit Agreement), whereby the Lenders have agreed to make certain loans
      to the Company, subject to the terms and conditions contained in the
      Credit Agreement.

B.    Pursuant to the terms of that certain Note and Stock Purchase Agreement of
      even date herewith (the "NOTE PURCHASE AGREEMENT") among the Credit
      Parties, Canpartners Investments IV, LLC, a California limited liability
      company (the "INITIAL PURCHASER") and the other purchasers party thereto
      from time to time (such other purchasers, together with the Initial
      Purchaser, are the "SUBORDINATED CREDITORS"), the Subordinated Creditors
      have agreed to make certain loans to the Company, subject to the terms and
      conditions contained in the Note Purchase Agreement.

C.    Pursuant to the terms of that certain Subordination and Intercreditor
      Agreement of even date herewith (the "INTERCREDITOR AGREEMENT") among the
      Credit Parties, the Agent (both as collateral agent under the
      Intercreditor Agreement and as Agent for the Lenders) and the Subordinated
      Creditors, the Lenders and the Subordinated Creditors have established,
      INTER ALIA, the relative rights and priority of liens of ----- ---- the
      Lenders and the Subordinated Creditors with respect to all real and
      personal property of any Credit Party pledged to secure either the Senior
      Debt or the Subordinated Debt (each as defined in the Intercreditor
      Agreement).

D.    The Company has requested that the Agent and the Lenders modify the Credit
      Agreement to permit the Company and the Holding Company to enter into the
      Note Purchase Agreement and to perform its obligations thereunder, subject
      to the terms of the Intercreditor Agreement, and the Agent and the Lenders
      are willing to agree to such


<PAGE>

      modifications, and to such other modifications as are specifically set
      forth herein, all subject to the terms and conditions of this Amendment.

                               STATEMENT OF TERMS

1.    AMENDMENTS TO CREDIT AGREEMENT. Subject to the terms and conditions set
forth in this Amendment, the provisions of the Credit Agreement recited below
are hereby amended as follows:

      1.1   Section 1.01 is hereby amended by adding the following definitions
thereto to be inserted in alphabetical order therein:

            "AFFILIATED INVESTOR" shall mean with respect to any Person, all
            other Persons the investment affairs of which are controlled or
            managed by the first Person.

            "COLLATERAL AGENT" shall have the meaning ascribed to such term in
            the Intercreditor Agreement, with the initial Collateral Agent being
            the Agent under this Agreement.

            "CURRENT RATIO" means at any time the ratio of (i) Consolidated
            Current Assets to (ii) Consolidated Current Liabilities, each as of
            the last day of the then most recently ended calendar month

            "INTERCREDITOR AGREEMENT" means the Subordination and Intercreditor
            Agreement dated as of September 15, 2000 among the Credit Parties,
            the Collateral Agent, the Agent (both as Collateral Agent for the
            Lenders and the Subordinated Creditors and as Agent for the Lenders)
            and the Subordinated Creditors.

            "IPO" means the closing of a Person's initial public offering of its
            shares under the Securities Act.

            "LENDER AFFILIATE" means, with respect to any Lender, (i) any Person
            that directly, or indirectly through one or more intermediaries,
            controls such Lender (a "CONTROLLING Lender") or (ii) any Person
            which is controlled by or is under common control with a Controlling
            Lender. As used herein, the term "control" of a Person means the
            possession, directly or indirectly, of the power to vote 10% or more
            of any class of voting securities of such Person or to direct or
            cause the direction of the management or policies of a Person,
            whether through the ownership of voting securities, by contract or
            otherwise.

            "MODIFICATION AGREEMENT" means the Security Documents Joinder and
            Modification Agreement dated as of September 15, 2000 among the
            Credit


                                       2
<PAGE>

            Parties, the Agent (both as Collateral Agent for the Lenders and the
            Subordinated Creditors and as Agent for the Lenders) and the
            Subordinated Creditors.

            "NOTE PURCHASE AGREEMENT" means the Note and Stock Purchase
            Agreement dated as of September 15, 2000 among the Credit Parties
            and the Subordinated Creditors, together with any modifications
            thereto made in conformance with the provisions of the Intercreditor
            Agreement.

            "PRIVATE EQUITY ISSUANCE" means any private issuance and sale of
            Common Stock or other equity securities.

            "SUBORDINATED CREDITORS" means the Persons who are from time to time
            purchasers under the Note Purchase Agreement, including the initial
            purchaser, Canpartners Investments IV, LLC, a California limited
            liability company.

            "SENIOR LEVERAGE RATIO" means at any time the ratio of (i)
            Consolidated Total Debt less Subordinated Debt at such time to (ii)
            Consolidated EBITDA minus Consolidated Capital Expenditures for the
            twelve months then most recently ended (considered as a single
            accounting period, and subject to Section 7.20).

            "SUBORDINATED DEBT" shall have the meaning ascribed to that term in
            the Intercreditor Agreement.

      1.2   Section 1.01 is hereby amended to delete the definitions of "ASSET
SALE", "DEBT", "EBITDA", "FINANCING DOCUMENTS", "GUARANTORS", "LEVERAGE RATIO",
"SECURITY DOCUMENTS" and "SOLVENT" and replace them with the following
definitions (and inserting such new definitions in alphabetical order therein):

            "ASSET SALE" means any sale, lease or other disposition (including
            any such transaction effected by way of merger or consolidation) by
            any Credit Party of any asset, but excluding (i) dispositions of
            inventory in the ordinary course of business and (ii) dispositions
            of Temporary Cash Investments and cash payments otherwise permitted
            under this Agreement; provided that a disposition of assets not
            excluded by clauses (i) or (ii) above during any Fiscal Year shall
            not constitute an Asset Sale unless and until (and only to the
            extent that), subject to the provisions of Section 6 of the
            Intercreditor Agreement: (x) the aggregate Net Cash Proceeds of such
            disposition of assets are not used for the purchase of reasonably
            equivalent replacements of such assets acquired or ordered within 90
            days thereof; or (y) the aggregate Net Cash Proceeds from such
            disposition (if not used as provided in clause (x) above), when
            combined with all other such dispositions previously made during
            such Fiscal Year and not used as provided in clause (x) above,
            exceeds $100,000.


                                       3
<PAGE>

            "DEBT" of a Person means at any date, without duplication all
            obligations of such Person which, in accordance with GAAP, would be
            included as a liability on the balance sheet of such Person
            including, without limitation, (i) all obligations of such Person
            for borrowed money, (ii) all obligations of such Person evidenced by
            bonds, debentures, notes or other similar instruments, (iii) all
            obligations of such Person to pay the deferred purchase price of
            property or services, except trade accounts payable arising and paid
            in the ordinary course of business, (iv) all Capital Leases of such
            Person, (v) all obligations of such Person to purchase securities
            (or other property) which arise out of or in connection with the
            issuance or sale of the same or substantially similar securities (or
            property), (vi) all contingent or non-contingent obligations of such
            Person to reimburse any bank or other Person in respect of amounts
            paid under a letter of credit or similar instrument, (vii) all
            equity securities of such Person subject to repurchase or redemption
            otherwise than at the sole option of such Person, (viii) all Debt
            secured by a Lien on any asset of such Person, whether or not such
            Debt is otherwise an obligation of such Person, (ix) all Debt of
            others Guaranteed by such Person, and (x) all obligations of such
            Person in respect of settlements (structured or otherwise) of any
            litigation involving such Person.

            "EBITDA" means, for any period and for any Person, the Consolidated
            Net Income of such Person and its consolidated subsidiaries for such
            period, after all expenses and other proper charges except
            depreciation, interest, amortization and income taxes, determined in
            accordance with GAAP (specifically including in the calculation
            thereof in the case of the Holding Company and its Consolidated
            Subsidiaries (x) any income or loss from discontinued operations and
            (y) the full amount of any charges incurred in such period related
            to the development of new business, whether expensed or capitalized)
            (A) eliminating, without duplication: (i) all intercompany items,
            (ii) all earnings attributable to equity interests in Persons that
            are not Subsidiaries of such Person unless actually received by such
            Person, (iii) all income arising from the forgiveness, adjustment,
            or negotiated settlement of any indebtedness, (iv) any extraordinary
            items of income or expense, (v) any increase or decrease in income
            arising from any change in such Person's method of accounting,
            subject (in the case of the Holding Company) to Section 1.02, and
            (vi) any interest income, and (B) deducting therefrom, to the extent
            not previously deducted in calculating Consolidated Net Income, any
            development costs incurred subsequent to the Closing Date, whether
            expensed or capitalized on the books of the Holding Company.

            "FINANCING DOCUMENTS" means this Agreement, the Notes, the Holding
            Company Guaranty Agreements, the Warrant, the Warrantholder's Rights


                                       4
<PAGE>

            Agreement, the Security Documents and the Intercreditor Agreement.

            "GUARANTORS" means, collectively, the Holding Company, each
            Subsidiary of the Holding Company, other than the Company, and each
            other Person who now or in the future guarantees the payment and
            performance of the Obligations.

            "SECURITY DOCUMENTS" means, collectively, the Security Agreements,
            the Pledge Agreements, the Pledged Account Agreements, any Mortgage,
            the Modification Agreement and any other agreement pursuant to which
            any Credit Party provides a Lien on its assets in favor of the
            Collateral Agent for the benefit of the Lenders and the Subordinated
            Creditors (in accordance with the provisions of the Intercreditor
            Agreement), and all supplementary assignments, security agreements,
            pledge agreements, acknowledgments or other documents delivered or
            to be delivered pursuant to the terms hereof or of any other
            Security Document.

            "SOLVENT" means , with respect to the Credit Parties on a particular
            date, that on such date (i) the assets of the Credit Parties, in the
            aggregate, at a fair valuation, will exceed their liabilities,
            including contingent liabilities, (ii) the remaining capital of the
            Credit Parties, in the aggregate, will not be unreasonably small to
            conduct their business, (iii) each of the Credit Parties separately
            will not have incurred debts, and will not intend to incur debts,
            beyond its ability to pay such debts as they mature, and (iv) the
            present fair saleable value of the assets of the Credit Parties, in
            the aggregate, is greater than their probable liability on its
            existing debts as such debts become absolute and matured. For
            purposes of this definition, "debt" means any liability on a claim,
            and "claim" means (i) right to payment, whether or not such right is
            reduced to judgment, liquidated, unliquidated, fixed, contingent,
            matured, unmatured, disputed, undisputed, legal, equitable, secured
            or unsecured, or (ii) right to an equitable remedy for breach of
            performance if such breach gives rise to a right to payment, whether
            or not such right to an equitable remedy is reduced to judgment,
            fixed, contingent, matured, unmatured, disputed, undisputed, secured
            or unsecured. In computing the amount of contingent liabilities of
            the Credit Parties on any date, such liabilities shall be computed
            at the amount that, in the judgment of the Required Lenders in light
            of all facts and circumstances existing at such time, represents the
            amount of such liabilities that reasonably can be expected to become
            actual or matured liabilities.

            "TOTAL LEVERAGE RATIO" means at any time the ratio of (i)
            Consolidated Total Debt at such time to (ii) Consolidated EBITDA
            minus Consolidated Capital Expenditures for the twelve months then
            most recently ended (considered as a single accounting period, and
            subject to Section 7.20).

      1.3   In Section 1.01,  the definition of  "Non-Guarantor  Subsidiaries"
is deleted in its entirety.


                                       5
<PAGE>

      1.4   In Section 1.01, in the definition of "Revolving Credit Commitment",
the dollar amount "$15,000,000" is deleted and replaced with the dollar amount
"$3,600,000".

      1.5   In Section 1.01, in the definition of "Solvent", the first sentence
thereof is hereby amended by (a) deleting "and" from the end of clause (ii), (b)
deleting the period from the end of clause (iii), and adding "; and" in its
place, and (c) adding to the end of such sentence a new clause "(iv)" as
follows:

            (iv) the present fair saleable value of the assets of such Person is
            greater than its probable liability on its existing debts as such
            debts become absolute and matured.

      1.6   Section 2.04(a) is amended to read in its entirety as follows:

                  (a) MANDATORY SCHEDULED PREPAYMENTS. Commencing on October 1,
            2000, and continuing on each Quarterly Date thereafter, the Company
            shall repay the Term Loans in quarterly installments of principal in
            the amount set forth for such Quarterly Date below, provided that
            there shall become due and the Company shall pay on the Term Loan
            Maturity Date the entire outstanding principal amount of the Term
            Loans, together with accrued and unpaid interest on the principal
            amount being repaid to but excluding the date of payment.

<TABLE>
<CAPTION>

                   Quarterly Date              Required Principal Payment
                   --------------              --------------------------
<S>                                            <C>
                   October 1, 2000             $500,000
                   January 1,2001              $500,000
                   April 1, 2001               $500,000
                   July 1, 2001                $500,000
                   October 1, 2001 (and on     $825,000
                   each Quarterly Date
                   thereafter)
</TABLE>

      1.7   Section 2.04(b) is amended to read in its entirety as follows:

                  (b) MANDATORY INCREMENTAL PREPAYMENTS. There shall become due
            and payable, and the Company shall prepay, an aggregate principal
            amount of the Term Loans (or, if less, the aggregate outstanding
            principal amount of the Term Loans) in the following amounts at the
            following times, and in the case of any prepayment of the remaining
            Term Loans in whole, accrued and unpaid interest on the principal
            amount being prepaid to but excluding the date of such payment:

                        (i) on the earlier of (x) the date the audited financial
            statements for each Fiscal Year are delivered in accordance with
            Section 6.01 and (y) 90 days following the last day of each Fiscal
            Year, beginning with the Fiscal Year ending December 31, 2000, the
            Company shall deliver to the Agent:


                                       6
<PAGE>

                              (A) until the earlier of (a) March 15, 2001, and
            (b) the date that the Holding Company has delivered an Officer's
            Certificate certifying that the Holding Company and its Consolidated
            Subsidiaries have achieved a Current Ratio of 1.1 to 1 (the "EXCESS
            CASH FLOW ADJUSTMENT DATE"), an amount equal to 60% of the Excess
            Cash Flow for such Fiscal Year; and

                              (B) after the Excess Cash Flow Adjustment Date, an
            amount equal to 87.5% of the Excess Cash Flow for such Fiscal Year.

                        (ii) promptly upon receipt by the Company or any other
            Credit Party, (x) 100% of any payment which constitutes Major
            Casualty Proceeds or (y) 100% of any payment under the Key-Person
            Life Insurance Policy, unless, in the case of Major Casualty
            Proceeds only, the Required Lenders shall otherwise direct (in which
            case the amount of such payment shall be deposited into the
            Insurance Account to be held and applied in accordance with Section
            5 of the Company Security Agreement);

                        (iii) (A) in the case of Private Equity Issuances, (x)
            50% of the first Five Million Dollars ($5,000,000) of Net Cash
            Proceeds from a Private Equity Issuance and (y) 100% of Net Cash
            Proceeds from a Private Equity Issuance in excess of Five Million
            Dollars ($5,000,000); and (B) in the case of an IPO or any
            subsequent public issuance of equity, (x) 62.5% of the first Thirty
            Million Dollars ($30,000,000) of the Net Cash Proceeds from such IPO
            or subsequent public issuance of equity and (y) 87.5% of Net Cash
            Proceeds from such IPO or subsequent public issuance in excess of
            Thirty Million Dollars ($30,000,000).

                        (iv) upon receipt by the Company or any other Credit
            Party of the Net Cash Proceeds of any Asset Sale, 100% of such Net
            Cash Proceeds; and

                        (v) promptly upon receipt by APS of a Capitated
            Beneficiary Adjustment payment, 100% of such Capitated Beneficiary
            Adjustment payment.

      1.8   In Section 3.01(b)(i)(A), the "Working Capital Commitment" is hereby
amended to be "2,500,000" instead of "$3,000,000".

      1.9   In Section 3.01(b)(i)(B), in each of the three places where the term
"Leverage Ratio" appears, such term is deleted and replaced with the phrase
"either the Total Leverage Ratio or the Senior Leverage Ratio".

      1.10  In Section 3.05, subsections (d), (e), (f), (g) and (h) are deleted
and replaced in their entirety with the following new subsection "(c)":

            (c) There shall become due and payable, and the Company shall
            prepay, an aggregate principal amount of the Revolving Credit Loans
            (or, if less, the


                                       7
<PAGE>

            aggregate outstanding principal amount of the Revolving Credit
            Loans) in the following amounts (less any portion thereof applied to
            the repayment of the Term Loans under Section 2.04) at the following
            times, and in the case of any prepayment of the remaining Revolving
            Credit Loans in whole, accrued and unpaid interest on the principal
            amount being prepaid to but excluding the date of such payment:

                        (i) on the earlier of (x) the date the audited financial
            statements for each Fiscal Year are delivered in accordance with
            Section 6.01 and (y) 90 days following the last day of each Fiscal
            Year, beginning with the Fiscal Year ending December 31, 2000, the
            Company shall deliver to the Agent:

                              (A) until the earlier of (a) March 15, 2001, and
            (b) the Excess Cash Flow Adjustment Date, an amount equal to 60% of
            the Excess Cash Flow for such Fiscal Year; and

                              (B) after the Excess Cash Flow Adjustment Date, an
            amount equal to 87.5% of the Excess Cash Flow for such Fiscal Year;

                        (ii) promptly upon receipt by the Company or any other
            Credit Party, (x) 100% of any payment which constitutes Major
            Casualty Proceeds or (y) 100% of any payment under the Key-Person
            Life Insurance Policy, unless, in the case of Major Casualty
            Proceeds only, the Required Lenders shall otherwise direct (in which
            case the amount of such payment shall be deposited into the
            Insurance Account to be held and applied in accordance with Section
            5 of the Company Security Agreement);

                        (iii) (A) in the case of Private Equity Issuances, (x)
            50% of the first Five Million Dollars ($5,000,000) of Net Cash
            Proceeds from a Private Equity Issuance and (y) 100% of Net Cash
            Proceeds from a Private Equity Issuance in excess of Five Million
            Dollars ($5,000,000); and (B) in the case of an IPO or any
            subsequent public issuance of equity, (x) 62.5% of the first Thirty
            Million Dollars ($30,000,000) of the Net Cash Proceeds from such IPO
            or subsequent public issuance of equity and (y) 87.5% of Net Cash
            Proceeds from such IPO or subsequent public issuance in excess of
            Thirty Million Dollars ($30,000,000);

                        (iv) upon receipt by the Company or any other Credit
            Party of the Net Cash Proceeds of any Asset Sale, 100% of such Net
            Cash Proceeds; and

                        (v) promptly upon receipt by APS of a Capitated
            Beneficiary Adjustment payment, 100% of such Capitated Beneficiary
            Adjustment payment.

      1.11  Section  3.08(a) is hereby  deleted and  replaced in its  entirety
with the following:


                                       8
<PAGE>

                  (a) The Revolving Credit Commitment shall reduce by the amount
            of each payment made or required to be made pursuant to Section
            3.05(c) or Section 3.06.

      1.12  At the end of Article V, there is added a new Section 5.24 reading
in its entirety as follows:

                  SECTION 5.24. SOLVENCY. The Credit Parties are Solvent.

      1.13  Section 6.01 is hereby amended by (i) deleting "and" from the end of
subsection (k), (ii) deleting the period from the end of subsection (l) and
adding "; and" in its place, and (iii) adding to the end of Section 6.01 new
subsections "(m)" and "(n)" as follows:

            (m) concurrently with delivery to the Subordinated Creditors, copies
            of any notice or other information (including, without limitation,
            the annual and quarterly budgets described in Section 6.01(c) of the
            Note Purchase Agreement), provided by any Credit Party to the
            Subordinated Creditors in accordance with the terms of the Note
            Purchase Agreement or any Note Document (as defined in the Note
            Purchase Agreement) or any Subordinated Creditor's Equity Document
            (as defined in the Intercreditor Agreement); and

            (n) within 5 Business Days after the Holding Company and its
            Consolidated Subsidiaries have achieved a Current Ratio of 1.1 to 1,
            an Officer's Certificate certifying as to such Current Ratio and as
            to the date on which such ratio was achieved.

      1.14  In Section 6.24, in the proviso, the phrase "this Agreement shall
not require" is deleted and replaced with the phrase "this Agreement shall
require".

      1.15  In Article VI, there is added to the end of such Article a new
Section 6.22 reading in its entirety as follows:

                  SECTION 6.26. INTEREST RATE CONTRACTS. By October 16, 2000,
            the Company shall obtain, and shall thereafter cause to be
            maintained for a period of not less than three years, one or more
            interest rate hedge agreements with respect to the Obligations,
            covering an aggregate notional amount of not less than one-half of
            the maximum principal amount of the Loans for a term through the
            Term Loan Maturity Date and otherwise on terms reasonably acceptable
            to the Required Lenders.

      1.16  Section 7.01 is hereby amended by (i) deleting "and" from the end of
subsection (d), (ii) deleting the period from the end of subsection (e) and
adding "; and" in its place, and (iii) adding to the end of Section 7.01 a new
subsection "(f)" as follows:

            (f) Debt of the Credit Parties under the Note Purchase Agreement in


                                       9
<PAGE>

            an aggregate principal amount at any time outstanding not to exceed
            $7,500,000.

      1.17  Section 7.07 is hereby amended to (i) delete in its entirety clause
(d) in the first sentence thereof (including the proviso following clause (d));
and (ii) delete in its entirety clause (ii) in the second sentence thereof.

      1.18  Section 7.04 is hereby amended to read in its entirety as follows:

            SECTION 7.04. RESTRICTED PAYMENTS. No Credit Party will directly or
            indirectly declare, order, pay, make or set apart any sum for any
            Restricted Payment, PROVIDED that the foregoing shall not restrict
            or prohibit: (a) dividends or distributions by the Company or the
            Holding Company at such times or in such amounts as are necessary to
            permit (i) purchases or redemptions of Warrants under the terms
            hereof, (ii) the pro rata distribution by a Credit Party of Net Cash
            Proceeds received by such Credit Party from the sale of any partial
            hospitalization assets to the Company and/or the Holding Company and
            the holders of the minority ownership interest in such Credit Party,
            or (iii) a distribution by the Company to the Holding Company in an
            amount not to exceed $100,000 in any one Fiscal Year for reasonable
            out of pocket operating costs and expenses; or (b) payments by the
            Company to the Subordinated Creditors with respect to the
            Subordinated Debt (and dividends or distributions from any
            Subsidiary of the Company to the Company to allow such payments to
            be made), to the extent that such payments are permitted under the
            provisions of the Intercreditor Agreement.

      1.19  Section 7.02 is hereby amended by (i) deleting "and" from the end of
subsection (b), (ii) deleting the period from the end of subsection (c) and
adding "; and" in its place, and (iii) adding to the end of Section 7.02 a new
subsection "(d)" as follows:

            (d) Liens securing the Subordinated Debt so long as such liens
            comply in all respects with the provisions of the Intercreditor
            Agreement.

      1.20  Section 7.14 is hereby amended to read in its entirety as follows:

            SECTION 7.14. CAPITAL EXPENDITURES. The aggregate amount of
            Consolidated Capital Expenditures shall not exceed (a) $3,200,000
            for the Fiscal Year ending December 31, 2000 and (b) $1,500,000 for
            any Fiscal Year thereafter.

      1.21  Section 7.15 is hereby amended to read in its entirety as follows:

            SECTION 7.15. TOTAL DEBT SERVICE COVERAGE RATIO. The Holding Company
            shall not permit the ratio determined as of the last day of any


                                       10
<PAGE>

            calendar month of (i) Consolidated Free Cash Flow to (ii) Total Debt
            Service, in each case for the twelve-month period then ended
            (provided, however, that in making such calculation, there shall be
            excluded any period of time prior to July 1, 2000) to be less than
            1.15 to 1.00; provided, however, that in calculating this financial
            covenant there shall be excluded from Total Debt Service the
            principal amortization payment scheduled to be paid on July 1, 2000.

      1.22  Section 7.16 is hereby amended to read in its entirety as follows:

            SECTION 7.16. LEVERAGE RATIOS.

                  (a) The Senior Leverage Ratio shall not (i) at any time from
            July 1, 2000 through December 31, 2000 exceed 3.25 to 1.00, (ii) at
            any time from January 1, 2001 through June 30, 2001 exceed 3.00 to
            1.00, (iii) at any time from July 1, 2001 through December 31, 2001
            exceed 2.50 to 1.00 and (iv) at any time thereafter exceed 2.00 to
            1.00.

                  (b) The Total Leverage Ratio shall not (i) at any time from
            July 1, 2000 through December 31, 2000 exceed 4.75 to 1.00, (ii) at
            any time from January 1, 2001 through June 30, 2001 exceed 4.50 to
            1.00, (iii) at any time from July 1, 2001 through December 31, 2001
            exceed 4.00 to 1.00 and (iv) at any time thereafter exceed 3.50 to
            1.00.

      1.23  Section 7.18 is hereby amended to read in its entirety as follows:

                  SECTION 7.18. INTEREST COVERAGE. The ratio, determined as of
            the last day of any calendar month, of (i) Consolidated EBITDA to
            (ii) the aggregate interest charges incurred by the Credit Parties,
            whether expensed or capitalized, including the portion of any
            obligation under Capital Leases allocable to interest expense in
            accordance with GAAP but excluding the portion of any debt discount
            or premium and the expenses of any debt issuance that shall be
            amortized in such period, in each case for the twelve-month period
            then ended (provided, however, that in making such calculation,
            there shall be excluded any period of time prior to July 1, 2000)
            shall not be less than (i) 2.25 to 1.00 at any time from July 1,
            2000 through December 31, 2001 and (ii) 2.50 to 1.00 of any time
            thereafter.

      1.24  Section 7.19 is hereby amended to read in its entirety as follows:

                  SECTION 7.19. MINIMUM EBITDA. The Holding Company shall not at
            any time during any period specified below permit Consolidated
            EBITDA for the twelve month period most recently ended (provided,
            however, that in making such calculation, there shall be excluded
            any period of time prior to July 1, 2000) to be less than the amount
            set forth opposite such period below:


                                       11
<PAGE>

<TABLE>
<CAPTION>

                  Period Ending                Consolidated EBITDA
                  -------------                -------------------
<S>                                            <C>
                  July 31, 2000                $497,000
                  August 31, 2000              $930,000
                  September 30, 2000           $1,530,000
                  October 31, 2000             $2,019,000
                  November 30, 2000            $2,508,000
                  December 31, 2000            $2,962,000
                  January 31, 2001             $3,663,000
                  February 28, 2001            $4,323,000
                  March 31, 2001               $4,552,000
                  April 30, 2001               $5,127,000
                  May 31, 2001                 $5,678,000
                  June 30, 2001                $6,458,000
                  July 31, 2001                $6,645,000
                  August 31, 2001              $6,809,000
                  September 30, 2001           $6,869,000
                  October 31, 2001             $6,975,000
                  November 30, 2001            $7,087,000
                  December 31, 2001            $7,240,000
                  January 31, 2002             $7,240,000
                  February 28, 2002            $7,240,000
                  March 31, 2002               $7,508,000
                  April 30, 2002               $7,564,000
                  May 31, 2002                 $7,651,000
                  June 30, 2002                $7,515,000
                  July 31, 2002                $7,556,000
                  August 31, 2002              $7,542,000
                  September 30, 2002           $7,546,000
                  October 31, 2002             $7,622,000
                  November 30, 2002            $7,698,000
                  December 31, 2002            $7,775,000
                  At any time thereafter       $7,800,000
</TABLE>

      1.25  Section 7.20 is hereby amended to read in its entirety as follows:

                  SECTION 7.20. TRANSITION RULES. In calculating compliance with
            Section 7.15 and 7.16, Consolidated Capital Expenditures for any
            period shall be calculated as (a) for periods through December 31,
            2000, the lesser of (i) $83,333 per month and (ii) actual
            Consolidated Capital Expenditures for such period; and (b) for the
            periods from and after January 1, 2001, actual Consolidated Capital
            Expenditures for each month. In calculating compliance with Section
            7.16, for all periods ending prior to July 1, 2001 the sum (the
            "SUM") of Consolidated EBITDA less Consolidated Capital Expenditures
            shall be calculated by multiplying the sum by twelve and dividing
            the resulting figure by the number of calendar


                                       12
<PAGE>

            months elapsed since July 1, 2000:

      1.26  Article VII is hereby amended by adding the following new Sections
7.22 and 7.23 to the end thereof:

                  SECTION 7.22. RESTRICTIVE AGREEMENTS. The Holding Company and
            the Company will not, and will not permit any of its Subsidiaries
            to, enter into any agreement (excluding this Agreement, the Note
            Purchase Agreement, the Intercreditor Agreement and any other
            Financing Document) prohibiting the ability of any Subsidiary to
            make any payment, directly or indirectly, to the Holding Company by
            way of dividends, advances, repayments of loans or advances,
            reimbursements of management and other intercompany charges,
            expenses and accruals or other returns on investments, or any other
            agreement or arrangement which restricts the ability of any such
            Subsidiary to make any payment, directly or indirectly, to the
            Holding Company; provided, however, that the Note Purchase Agreement
            (and related documents) may not prohibit dividends and distributions
            from any Subsidiary to the Company to enable the Company to make
            payments to the Agent or any Lender required by the Financing
            Documents.

                  SECTION 7.23. EQUITY SECURITIES ISSUANCES TO EMPLOYEES AND
            MANAGEMENT. The Holding Company shall not issue shares of Common
            Stock, Preferred Stock, options, warrants or any other equity
            securities to any employee or member of management of any Credit
            Party for a purchase or exercise price less than fair market value
            as determined by independent members of the Holding Company's board
            of directors.

      1.27  Section 8.01(k) is hereby amended by deleting therein the phrase
", except for any Joint Venture acquired in accordance with Section 7.07,".

      1.28  Section 8.01 is hereby amended by (i) deleting "or" from the end of
subsection (o), (ii) deleting the period from the end of subsection (p) and
adding a semicolon in its place, and (iii) adding to the end of Section 8.01 new
subsections "(q)" and "(r)" as follows:

            (q)   The Agent  shall  receive  an  Enforcement  Notice (as
            defined in the Intercreditor Agreement); or

            (r) An event of default shall occur under the terms of the Note
            Purchase Agreement or any Note Document (as defined in the Note
            Purchase Agreement).

      1.29  Section  11.06 is hereby  amended to add to the end  thereof,  the
following new subsection "(i)":

                  (i) Notwithstanding anything to the contrary in this Section
            11.06, no Lender shall assign any portion of its Note except to
            either (i) a Person who is a


                                       13
<PAGE>

            Lender Affiliate or Affiliated Investor; or (ii) a Person who will,
            immediately after giving effect to the assignment, hold Notes with
            an aggregate principal amount (including the undrawn portion of any
            Revolving Credit Commitment) of at least Two Million Five Hundred
            Thousand Dollars ($2,500,000). If the transfer is made to a Lender
            Affiliate or an Affiliated Investor and, after the assignment, such
            assignee shall fail, for any reason, to remain a Lender Affiliate or
            Affiliated Investor of a Person then a Lender, then, unless the
            assignee then holds at least $2,500,000 in aggregate principal
            amount (including the undrawn portion of any Revolving Credit
            Commitment) of the Loans, either (a) the assignee shall sell the
            assigned Notes back to the assigning Lender for the then outstanding
            principal balance of thereof, together with any accrued but unpaid
            interest thereon or (b) the other Lenders shall transfer a
            sufficient amount of their Notes and their interests in the
            Financing Documents to such assignee so that the assignee holds at
            least $2,500,000 in aggregate principal amount (including the
            undrawn portion of any Revolving Credit Commitment) of the Loans.

      1.30  Notwithstanding anything to the contrary in the Credit Agreement:
(i) no further Acquisition Loans shall be made available to the Company; (ii)
the Acquisition Loan Availability shall be deemed to be "zero" from and after
the date of this Amendment (but such reduction shall not obligate the Company to
make a mandatory prepayment of the Acquisition Loans under Section 3.05(b)(2) of
the Credit Agreement); (iii) all of the outstanding Acquisition Loans are hereby
deemed to be converted to Term Loans (regardless of whether the aggregate of the
existing Term Loans and Acquisition Loans may exceed the Term Loan Commitment
recited in the Credit Agreement) and as Term Loans shall be due and payable in
accordance with the provisions set forth in the Credit Agreement with respect to
Term Loans; (iv) after giving effect to the conversion of the Acquisition Loans
to Term Loans as set forth herein, the outstanding principal balance of the
Acquisition Loans shall not be taken into account in determining Working Capital
Availability; (v) the definition of "Amortization Commencement Date" in Section
1.01 of the Credit Agreement and the entire Section 3.05(c) of the Credit
Agreement are each hereby deleted; and (vi) the promissory notes issued with
respect to the Acquisition Loans shall continue to evidence the sums due to the
Lenders under the Acquisition Loans as converted to Term Loans.

      1.31  Notwithstanding anything to the contrary in the Credit Agreement,
wherever in the Credit Agreement it is recited that (i) Liens have been (or are
to be) granted to the Agent to secure the Obligations, it shall be deemed
instead to require that such Liens be granted to the Collateral Agent, for the
benefit of the Lenders and the Subordinated Creditors, pursuant to the
provisions of the Security Documents subject to the Intercreditor Agreement
(provided, however, that any Liens granted to the Agent in the Key-Person Life
Insurance Policy shall continue to be held by the Agent solely for the benefit
of the Lenders); and (ii) any action is to be taken or any decision is to be
made by the Agent with respect to the Collateral, such action or decision shall
instead be taken by the Collateral Agent consistent with the provisions of the
Intercreditor Agreement and the Security Documents (provided, however, that any
action or decisions regarding the Key-Person Life Insurance Policy shall
continue to be taken by the Agent solely for the benefit of the Lenders).


                                       14
<PAGE>

      2.    WAIVERS OF SPECIFIED EXISTING DEFAULTS. Subject to the terms and
conditions of this Amendment, the Agent and the Lenders hereby waive the
following specified Defaults or Events of Default: (i) the late delivery of
financial statements under Sections 6.01(a) and (b) with respect to any periods
ending on or before June 30, 2000 (which financial statements have since been
delivered to the Agent); and (ii) any failure of the Company to comply with the
covenants set forth in Sections 7.15, 7.16, 7.17, 7.18 and 7.19 with respect to
any periods ending on or before June 30, 2000.

      3.    REPRESENTATIONS AND WARRANTIES. Each of the Credit Parties hereby
represents and warrants to the Agent and the Lenders that (a) this Amendment has
been duly authorized, executed and delivered by the Company and the Holding
Company, (b) after giving effect to the modifications set forth in Section 1 of
this Amendment and the waivers set forth in Section 2 of this Amendment, no
Default or Event of Default has occurred and is continuing as of this date, (c)
all of the representations and warranties made by each of the Company and the
Credit Parties in the Credit Agreement are true and correct in all material
respects on and as of the date of this Amendment (except to the extent that any
such representations or warranties expressly referred to a specific prior date),
and (d) the financial projections attached hereto as Exhibit A were prepared in
good faith by the Credit Parties based upon reasonable assumptions, and the
Credit Parties acknowledge that the Agent and the Lenders are relying on such
projections in deciding to enter into this Amendment. Any breach by any Credit
Party of its representations and warranties contained in this Section shall be
an Event of Default for all purposes of the Credit Agreement.

      4.    RATIFICATION. Each of the Credit Parties hereby ratifies and
reaffirms each and every term, covenant and condition set forth in the Credit
Agreement and all other documents delivered by any of the Credit Parties in
connection therewith (including without limitation the other Financing Documents
to which any of the Credit Parties is a party).

      5.    ESTOPPEL. To induce the Agent and the Lenders to enter into this
Amendment, each of the Credit Parties hereby acknowledges and agrees that, as of
the date hereof, there exists no right of offset, defense or counterclaim in
favor of any Credit Party as against the Collateral Agent, the Agent or any
Lender with respect to the obligations of any Credit Party to any of such
parties under the Credit Agreement or the other Financing Documents, either with
or without giving effect to this Amendment.

      6.    CONDITIONS TO EFFECTIVENESS. The amendments contained in Section 1
hereof and the waivers in Section 2 hereof shall become effective upon the date
of this Amendment, subject to the satisfaction of the following conditions on or
prior to such date:

      (a) the receipt by the Agent of this Amendment, duly executed, completed
      and delivered by the Agent, the Lenders and each of the Credit Parties;

      (b) the receipt by the Agent of a true and complete copy of the Note
      Purchase Agreement, duly executed by the Credit Parties and the
      Subordinated Creditors (together with all of the other Note Documents, as
      defined in the Note Purchase


                                       15
<PAGE>

      Agreement, and the Subordinated Creditor's Equity Documents, as defined in
      the Intercreditor Agreement) and the Company shall have contemporaneously
      received the sum of $7,115,142 from the issuance of Notes;

      (c) the receipt by the Agent of a fully executed Intercreditor Agreement;

      (d) the receipt by the Agent of a fully executed Modification Agreement
      (together with copies of all documents required to be delivered pursuant
      thereto);

      (e) the receipt by the Agent of all fees and expenses (including attorneys
      fees) incurred by the Agent in connection with the Financing Documents,
      including those related to the negotiation and execution of this
      Amendment; and

      (f)   the  receipt  by the Agent of such other  documents  as the Agent
      may reasonably request.

      7.    REIMBURSEMENT OF EXPENSES. The Credit Parties hereby agree, jointly
and severally, that the Credit Parties will reimburse the Agent and the Lenders
on demand for all costs and expenses (including without limitation attorney's
fees) incurred by such parties in connection with the negotiation, documentation
and consummation of this Amendment and the other documents executed in
connection herewith and the transactions contemplated hereby and thereby.

      8.    GOVERNING LAW. THIS  AMENDMENT  SHALL BE GOVERNED BY AND CONSTRUED
IN  ACCORDANCE  WITH THE LAWS OF THE STATE OF  GEORGIA  WITHOUT  REGARD TO ITS
PRINCIPLES OF CONFLICTS OF LAWS.

      9.    SEVERABILITY OF PROVISIONS. Any provision of this Amendment which is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof or affecting the validity or
enforceability of such provision in any other jurisdiction. To the extent
permitted by applicable law, each Credit Party hereby waive any provision of law
that renders any provision hereof prohibited or unenforceable in any respect.

      10.   COUNTERPARTS; FACSIMILE DELIVERY. This Amendment may be executed in
any number of counterparts, all of which shall be deemed to constitute but one
original and shall be binding upon all parties, their successors and permitted
assigns. This Amendment may be delivered by facsimile transmission with the same
effect as if originally executed counterparts of this Agreement were personally
delivered to each of the parties hereto.

      11.   ENTIRE AGREEMENT. The Credit Agreement, as amended by this
Amendment, together with the Intercreditor Agreement and the Modification
Agreement embodies the entire agreement between the parties hereto relating to
the subject matter hereof and supersedes all prior agreements, representations
and understandings, if any, relating to the subject matter thereof.


                                       16
<PAGE>

      IN WITNESS WHEREOF, the parties have caused this Amendment to be duly
executed by their respective officers, as of the date first above written.


PSYCH SYSTEMS HOLDINGS, INC.          AMERICAN PSYCH SYSTEMS
                                      HOLDINGS, INC.

By: /s/ Stephen DaRe                  By: /s/ Stephen DaRe
   -------------------------             -----------------------
Name: Stephen DaRe                    Name: Stephen DaRe
Title: EVP & CFO                      Title: EVP & CFO


BANK OF AMERICA, N.A., successor in   BANK OF AMERICA, N.A. , successor
interest to Banc of America           in interest to Banc of America
Commercial Finance Corporation,       Commercial Finance Corporation,
formerly known as NationsCredit       formerly known as NationsCredit
Commercial Corporation                Commercial Corporation
(as Agent)                            (as Lender)


By:_________________________          By:_________________________
Name:                                 Name:
Title:                                Title:



                       [Signatures continued on next page]



<PAGE>




AMERICAN PSYCH SYSTEMS, INC.
AMERICAN PSYCH SYSTEMS OF PUERTO RICO, INC.
AMERICAN PSYCH SYSTEMS OF TEXAS, INC.
AZCARE, INC.
CH/ECP SYSTEMS, INC.
CHS MANAGED SERVICES, INC.
METROPOLITAN IPA, INC.
NEW YORK PSYCH SYSTEMS, INC.
NEW YORK PSYCH SYSTEMS, L.P.
       By: NEW YORK PSYCH SYSTEMS, INC., its General Partner
PSYCH SYSTEMS IPA, INC.
PSYCH SYSTEMS OF MANHATTAN, INC.
PSYCH SYSTEMS OF LONG ISLAND, INC.
PSYCH SYSTEMS OF WESTCHESTER, INC.
PSYCH SYSTEMS PPO, INC.
SUFFOLK PSYCH SYSTEMS, L.P.
       By: NEW YORK PSYCH SYSTEMS, INC., its General Partner
VYDAS RESOURCES, INC.
WESTCHESTER PSYCH SYSTEMS, L.P.
       By: NEW YORK PSYCH SYSTEMS, INC., its General Partner



By: /s/ Stephen DaRe
   --------------------------
Name: Stephen DaRe
Title: EVP & CFO