Document:

<PAGE>
                                                                     EXHIBIT 4.9

                                 AMENDMENT NO. 2
               TO AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT

         THIS AMENDMENT NO. 2 TO AMENDED AND RESTATED INVESTORS' RIGHTS
AGREEMENT ("Amendment") is made and entered into as of April 1, 2002, by and
among SYMBION, INC., a Tennessee corporation formerly named "UniPhy Healthcare,
Inc." (the "Company"), J.H. WHITNEY III, L.P. ("JHW III"), J.H. WHITNEY IV, L.P.
("JHW IV"), WHITNEY STRATEGIC PARTNERS III, L.P. ("WSP" and together with JHW
III and JHW IV, the "Whitney Shareholders"), those persons holding five percent
(5%) or more of the outstanding capital stock of Physicians Surgical Care, Inc.,
a Delaware corporation ("PSC"), immediately prior to the closing of the Merger
(defined herein) as identified on Exhibit A attached hereto (the "PSC
Shareholders") and the other persons identified on Exhibit A (collectively, the
"Original Investors" and each individually, an "Original Investor"). The Whitney
Shareholders, the PSC Shareholders and the Original Investors are referred to
herein collectively as the "Investors."

                                R E C I T A L S:

         WHEREAS, the Company and the Original Investors are parties to that
certain Amended and Restated Investors' Rights Agreement, dated as of June 25,
1999 as amended by the Amendment No. 1 to Amended and Restated Investors' Rights
Agreement, dated as of August 11, 1999 (the "Investors' Rights Agreement");

         WHEREAS, the Company, PSC and Symbion Acquisition Sub, Inc. ("SAS") are
parties to that certain Agreement and Plan of Merger, dated as of March 7, 2002
(the "Merger Agreement") which provides, among other things, for SAS to be
merged with and into PSC (the "Merger");

         WHEREAS, it is a condition of PSC's obligations under the Merger
Agreement that the Company and the Original Investors amend the Investors'
Rights Agreement to add the Whitney Shareholders as parties thereto and to
provide the Whitney Shareholders with rights and obligations that are pari passu
with those of the ARC Key Shareholders and the UniPhy Preferred Shareholders as
well as all of the other rights of the Investors and the Anti-Dilution Investors
thereunder and to provide to the PSC Shareholders the rights and obligations of
an "Investor" solely for the purposes of Sections 2.3, 2.5, 2.6, 2.7, 2.8; 2.9,
2.10, 2.11, 2.12, 2.13, 2.14 and 3.1(b) of the Investors' Rights Agreement;

         WHEREAS, the Company and the Investors desire to amend the Investors'
Rights Agreement as set forth in this Amendment, pursuant to Section 6.5 of the
Investors' Rights Agreement; and

         NOW, THEREFORE, in consideration of the foregoing and the respective
covenants and agreements contained herein, the sufficiency of which is hereby
acknowledged, the parties hereby agree and consent to the following:

<PAGE>

1.       Definitions.

         (a)      Capitalized terms used herein without definition shall have
the same meanings ascribed to such terms in the Investors' Rights Agreement.

         (b)      The Investors' Rights Agreement is hereby amended by adding
the following as part of Section 1 in appropriate alphabetical order:

                  "Affiliate" shall mean (i) in the case of an entity, any
         Person who or which, directly or indirectly, through one or more
         intermediaries, controls or is controlled by, or is under common
         control with, any specified Person or (ii) in the case of an
         individual, such individual's spouse, children, grandchildren or
         parents or a trust primarily for the benefit of any of the foregoing.

                  "Preferred Stock" means the Series A Preferred Stock and the
         Series B Preferred Stock.

                  "Series A Preferred Stock" means the Series A Convertible
         Preferred Stock, par value $.01 per share, of the Company.

                  "Series B Preferred Stock" means the Series B Convertible
         Preferred Stock, par value $.01 per share, of the Company.

         (c)      The definition of "Registerable Securities" contained in
Section 1.1 of the Investors' Rights Agreement is hereby deleted in its entirety
and the following is hereby substituted therefor for all purposes:

                  "Registerable Securities" means (i) any and all shares of
         Common Stock of the Company held by the Investors or issued or issuable
         upon conversion of shares of Preferred Stock and any shares of Common
         Stock issued or issuable upon conversion of any shares of preferred
         stock; (ii) any other shares of Common Stock acquired or owned by any
         of the Investors prior to the Initial Offering if such Investor is an
         Affiliate of the Company; (iii) any Common Stock of the Company issued
         as (or issuable upon the conversion or exercise of any warrant, right
         or other security which is issued as) a dividend or other distribution
         with respect to, or in exchange for or in replacement of, such
         above-described securities; and (iv) any Common Stock of the Company
         issued upon conversion of any warrant, right or other security held by
         the Investors.

2.       Restrictions on Transfer. The Investors' Rights Agreement is hereby
further amended by adding and appending the following sentence at the end of
Section 2.1(b):

                  In addition, notwithstanding the provisions of paragraphs
         (a)(i) and (a)(ii) above, no such registration statement or opinion of
         counsel shall be necessary for a transfer by a Whitney Shareholder,
         UniPhy Preferred Shareholder or ARC Key Shareholder to any of its
         Affiliates if such transfer does not constitute a sale, provided the
         transferee will be subject to this Agreement to the same extent as if
         he were an original Investor hereunder.

                                       2
<PAGE>

3.       Demand Registration Rights. Section 2.2(a) of the Investors' Rights
Agreement is hereby deleted in its entirety and the following is hereby
substituted therefor for all purposes:

                  (a)      Subject to the conditions of this Section 2.2, if the
         Company shall receive at any time a written request from any UniPhy
         Preferred Shareholders, ARC Key Shareholders or Whitney Shareholders
         (for purposes of this Section 2.2, the "Demand Registration Investors")
         holding ten percent (10%) or more of the Registrable Securities then
         outstanding which are held by the Demand Registration Investors (the
         "Initiating Investors") that the Company file a registration statement
         under the Securities Act covering the registration of the Registrable
         Securities having an aggregate offering price to the public of not less
         than $1,000,000, then the Company shall, within thirty (30) days of the
         receipt thereof, give written notice of such request to all of the
         Demand Registration Investors, and subject to the limitations of this
         Section 2.2, use its best efforts to effect, as soon as practicable,
         the registration under the Securities Act of all Registrable Securities
         that the Demand Registration Investors request to be registered.

4.        Piggyback Registration Rights.

                  (a)      Section 2.3(a)(i) of the Investor' Rights Agreement
         is hereby deleted in its entirety and the following is hereby
         substituted therefor for all purposes:

                           (i)      In the case of the Initial Offering, no such
                  reduction shall reduce the securities being offered by the
                  Company for its own account to be included in the registration
                  and underwriting, and in no event shall the amount of
                  securities of the selling Investors included in the
                  registration be reduced below fifteen percent (15%) of the
                  total amount of securities included in such registration,
                  unless such offering is the Initial Offering and such
                  registration does not include shares of any other selling
                  shareholders, in which event any or all of the Registrable
                  Securities of the Investors may be excluded and in no event
                  will shares of any other selling shareholders be included in
                  such registration which would reduce the number of shares
                  which may be included by Investors without the written consent
                  of Investors holding not less than seventy-five percent (75%)
                  of the Registrable Securities held collectively by the UniPhy
                  Preferred Shareholders, the ARC Key Shareholders and the
                  Whitney Shareholders, and seventy-five (75%) of the
                  Registrable Securities by the UniPhy Founders proposed to be
                  sold in the offering.

                  (b)      Section 2.3(a)(ii) of the Investors' Rights Agreement
         is hereby deleted in its entirety and the following is hereby
         substituted therefor for all purposes:

                           (ii)     In the case of an underwritten primary
                  registration on behalf of the Company, the number of shares
                  that may be included in the underwriting shall be allocated,
                  first, to the Company; second to the UniPhy Preferred
                  Shareholders, the ARC Key Shareholders and the Whitney
                  Shareholders on a pro rata basis based on the total number of
                  Registrable Securities held by such UniPhy Preferred
                  Shareholders, ARC Key Shareholders and Whitney Shareholders;
                  third, to the UniPhy Founders on a pro rata basis based on the
                  total number of Registrable Securities held by the UniPhy
                  Founders; and fourth, to any shareholder of the Company (other
                  than an Investor) on a pro rata basis;

                                       3
<PAGE>

5.       Indemnification. The last proviso in Section 2.9(b) of the Investors'
Rights Agreement is hereby deleted in its entirety and the following is hereby
substituted therefor for all purposes:

                  provided further, that in no event shall any indemnity under
         this Section 2.9(b) exceed the proceeds from the offering received by
         such Investor.

6.       Assignment of Registration Rights. The term "affiliate" in Section 2.10
of the Investors' Rights Agreement is hereby deleted and the term "Affiliate" is
hereby substituted therefor for all purposes.

7.       Amendment of Registration Rights. The first sentence of Section 2.11 of
the Investors' Rights Agreement is hereby deleted in its entirety and the
following is hereby substituted therefor for all purposes:

                  Any provision of this Section 2 may be amended and the
         observance thereof may be waived (either generally or in a particular
         instance and either retroactively or prospectively), only with the
         written consent of the Company and the Investors owning at least
         two-thirds of the Registerable Securities then outstanding and, to the
         extent that any such amendment would adversely effect the UniPhy
         Founders, the written consent of the Investors' holding at least
         two-thirds of the Registerable Securities held by the UniPhy Founders;
         provided, however, that if any such amendment, waiver, discharge or
         termination shall in any way have an adverse or deleterious effect on
         the Whitney Shareholders, such amendment, waiver, discharge or
         termination shall require the Whitney Shareholders' prior written
         consent.

8.       Covenants of the Company. Section 3.1(c) of the Investors' Rights
Agreement is hereby deleted in its entirety and the following is hereby
substituted therefor for all purposes:

                  (c)      So long as a UniPhy Preferred Shareholder, ARC Key
         Shareholder (with its affiliates) or the Whitney Shareholders shall own
         not fewer than 110,000 shares of Registrable Securities (as adjusted
         for splits and combinations) (a "Major Investor") the Company will
         furnish each such Major Investor, as soon as practicable after the end
         of the first, second and third quarterly accounting periods in each
         fiscal year of the Company, and in any event within forty-five (45)
         days thereafter, a consolidated balance sheet of the Company as of the
         end of each such quarterly period, and a consolidated statement of
         income and a consolidated statement of cash flows of the Company for
         such period and for the current fiscal year to date, prepared in
         accordance with generally accepted accounting principles, with the
         exception that no notes need be attached to such statements and
         year-end audit adjustments may not have been made.

                                       4
<PAGE>

9.       Issuance of Additional Shares on Certain Dilutive Issues. The first
paragraph of Section 4.1 of the Investors' Rights Agreement is hereby deleted in
its entirety and the following is hereby substituted therefor for all purposes:

                  4.1.     Issuance of Additional Shares on Certain Dilutive
         Issues. In the event that, at any time prior to the closing of the
         Initial Offering, the consideration per share (determined pursuant to
         Section 4.1.4 below) for any Additional Share of Common Stock (as
         defined below) issued or deemed to be issued by the Company (the
         "Anti-Dilution Price") is less than the average price per share of the
         shares of Common Stock (or Preferred Stock that was converted to Common
         Stock) or Preferred Stock owned by each Investor identified on Exhibit
         A hereto as an anti-dilution Investor (the "Anti-Dilution Investors")
         at the time of the issuance giving rise to the issuance of additional
         shares pursuant to this Section 4.1 (the "Average Original Price"),
         then the Company shall issue to the Anti-Dilution Investors additional
         shares of Common Stock subject to the following provisions;

10.      Issuance of Additional Shares of Common Stock to Anti-Dilution
Investors upon Issuance of Additional Shares of Common Stock. Section 4.1.3 of
the Investors' Rights Agreement is hereby deleted in its entirety and the
following is hereby substituted therefor for all purposes:

                  4.1.3.   Issuance of Additional Shares of Common Stock to
         Anti-Dilution Investors Upon Issuance of Additional Shares of Common
         Stock. In the event that the Company at any time after the date hereof
         shall issue Additional Shares of Common Stock (including Additional
         Shares of Common Stock deemed to be issued pursuant to Subsection 4.1.2
         above), without consideration or for a consideration per share less
         than the Average Original Price, the Company shall issue to each
         Anti-Dilution Investor without further consideration, that number of
         Additional Shares of Common Stock equal to the result obtained by (a)
         dividing (i) the number of shares of Common Stock held by such
         Anti-Dilution Investor or Common Stock that an Anti-Dilution Investor
         could acquire upon conversion of any convertible preferred stock held
         by such Anti-Dilution Investor immediately prior to the issuance giving
         rise to the issuance of additional shares pursuant to this Section 4.1
         multiplied by its Average Original Price by (ii) the Anti-Dilution
         Price per share consideration received (or deemed to have been received
         pursuant to Section 4.1.2 above) by the Company for the Additional
         Shares of Common Stock and (b) subtracting from the quotient the number
         of shares of Common Stock held by each Anti-Dilution Investor and
         Common Stock that an Anti-Dilution Investor could acquire upon
         conversion of any convertible preferred stock held by such
         Anti-Dilution Investor immediately prior to the issuance giving rise to
         the issuance of additional shares pursuant to this Section 4.1.

                                       5
<PAGE>

11.      Rights of First Refusal. Section 4.2.1 of the Investors' Rights
Agreement is hereby deleted in its entirety and the following is hereby
substituted therefor for all purposes:

                  4.2.1    Subsequent Offerings. Each UniPhy Preferred
         Shareholder, ARC Key Shareholder and Whitney Shareholder (for purposes
         of this Section 4.2, the "First Refusal Investors") shall have a right
         of first refusal to purchase its pro rata share of all Equity
         Securities, as defined below, that the Company may, from time to time,
         propose to sell and issue after the date of this Amended and Restated
         Agreement, other than the Equity Securities excluded by Section 4.5
         hereof. Each First Refusal Investor's pro rata share is equal to the
         ratio of (A) the number of shares of the Company's Common Stock
         (assuming conversion of all Preferred Stock owned by such First Refusal
         Investor) of which such First Refusal Investor is deemed to be a holder
         immediately prior to the issuance of such Equity Securities to (B) the
         total number of shares of the Company's outstanding Common Stock
         (assuming conversion of all outstanding Preferred Stock) immediately
         prior to the issuance of the Equity Securities. The term "Equity
         Securities" shall mean (i) any Common Stock, preferred stock or other
         security of the Company, (ii) any security convertible, with or without
         consideration, into any Common Stock, preferred stock or other security
         (including any option to purchase such a convertible security), (iii)
         any security carrying any warrant or right to subscribe to or purchase
         any Common Stock, preferred stock or other security or (iv) any such
         warrant or right.

12.      Issuance of Equity Securities to Other Persons. The first sentence of
Section 4.2.3 is hereby deleted in its entirety and the following is hereby
substituted therefor for all purposes:

                  If not all of the First Refusal Investors elect to purchase
         their pro rata share of the Equity Securities then the Company shall
         promptly notify in writing the First Refusal Investors who do elect and
         shall offer such First Refusal Investors the right to acquire such
         unsubscribed shares.

13.      Amendment and Waiver. Section 6.5 of the Investors' Rights Agreement is
hereby deleted in its entirety and the following is hereby substituted therefor
for all purposes:

         6.5      Amendment and Waiver.

                  (a)      Except as otherwise expressly provided, this Amended
         and Restated Agreement may be amended or modified only upon the written
         consent of the Company and (i) the Investors holding at least
         seventy-five percent (75%) of the Registrable Securities held by the
         UniPhy Preferred Shareholders and the ARC Key Shareholders, (ii) the
         Investors holding at least seventy-five percent (75%) of the
         Registrable Securities held by the UniPhy Founders and (iii) the
         Investors holding at least seventy-five percent (75%) of the
         Registrable Securities held by the Whitney Shareholders; provided,
         however, (i) with respect to provisions of this Amended and Restated
         Agreement applicable only to the UniPhy Preferred Shareholders, the ARC
         Key Shareholders and the Whitney Shareholders, such provisions may be
         amended and modified solely upon the written consent of the Company and
         (x) the holders of at least seventy-five percent (75%) of the
         Registrable Securities held by the UniPhy Preferred Shareholders and
         the ARC Key Shareholders and (y) the holders of at least seventy-five
         percent (75%) of the Registrable Securities held by the Whitney

                                       6
<PAGE>

         Shareholders and (ii) with respect to provisions of this Amended and
         Restated Agreement applicable only to UniPhy Founders, such provisions
         may be amended and modified solely upon the written consent of the
         Company and the holders of at least seventy-five percent (75%) of the
         Registrable Securities held by the UniPhy Founders.

                  (b) Except as otherwise expressly provided, the obligations of
         the Company and the rights of the Investors under this Amended and
         Restated Agreement may be waived only with the written consent of (i)
         the Investors holding at least seventy-five percent (75%) of the
         Registrable Securities held by the UniPhy Preferred Shareholders and
         the ARC Key Shareholders, (ii) the Investors holding at least
         seventy-five percent (75%) of the Registrable Securities held by the
         UniPhy Founders and (iii) the Investors holding at least seventy-five
         percent (75%) of the Registrable Securities held by the Whitney
         Shareholders; provided, however, (i) with respect to the rights held
         only by the UniPhy Preferred Shareholders, the ARC Key Shareholders and
         the Whitney Shareholders, such rights may be waived solely upon the
         written consent of (x) the holders of at least seventy-five percent
         (75%) of the Registrable Securities held by the UniPhy Preferred
         Shareholders and the ARC Key Shareholders and (y) the holders of at
         least seventy-five percent (75%) of the Registrable Securities held by
         the Whitney Shareholders, and (ii) with respect to the rights held only
         by the UniPhy Founders, such rights may be waived solely upon the
         written consent of the holders of at least seventy-five percent (75%)
         of the Registrable Securities held by the UniPhy Founders.

14.      Whitney Amendment. The Investors' Rights Agreement is hereby amended by
adding and appending the following as Section 10 of the Investors' Rights
Agreement:

         10.      Addition of each of the Whitney Shareholders as a Party.
         Notwithstanding the provisions of Section 6.5 or any other Section
         hereof, upon the closing of the Merger:

                  (a)      Each of the Whitney Shareholders shall be a party to
         this Amended and Restated Agreement; and

                  (b)      Exhibit A attached to this Amended and Restated
         Agreement shall be amended to add each of the Whitney Shareholders as a
         person identified thereon, and each of the Whitney Shareholders shall
         be, and shall be included within the definition of, an "Investor" for
         purposes of this Amended and Restated Agreement; and

                  (c)      Exhibit A attached to this Amended and Restated
         Agreement shall be amended to identify each of the Whitney Shareholders
         as an "Anti-Dilution Investor," and each of the Whitney Shareholders
         shall be, and shall be included within the definition of, an
         "Anti-Dilution Investor" for purposes of this Amended and Restated
         Agreement; and

                  (d)      Exhibit A attached to this Amended and Restated
         Agreement shall be appended to identify each of JHW III, JHW IV and WSP
         as the "Whitney Shareholders," for purposes of this Amended and
         Restated Agreement; and

                                       7
<PAGE>

                  (e)      Whitney shall have, and be entitled and subject to,
         all of the rights, benefits, duties and obligations of an "Investor,"
         and an "Anti-Dilution Investor" under this Amended and Restated
         Agreement, subject to the terms hereof.

15.      Addition of the PSC Shareholders as Parties. The Investors' Rights
Agreement is hereby further amended by adding and appending the following as
Section 11, thereunder, of the Investors' Rights Agreement:

         11.      Addition of the PSC Shareholders as Parties. Notwithstanding
         the provisions of Section 6.5 or any other Section hereof, upon the
         closing of the Merger:

                  (a)      the PSC Shareholders shall be a party to this Amended
         and Restated Agreement; and

                  (b)      Exhibit A attached to this Amended and Restated
         Agreement shall be amended to add the PSC Shareholders as persons
         identified thereon, and the PSC Shareholders shall be, and shall be
         included within the definition of, an "Investor" solely for purposes
         Sections 2.3, 2.5, 2.6, 2.7, 2.8; 2.9, 2.10, 2.11, 2.12, 2.13, 2.14 and
         3.1(b) of this Amended and Restated Agreement; and

                  (c)      the PSC Shareholders shall have, and shall be
         entitled and subject to, all of the rights, benefits, duties and
         obligations of an "Investor" as provided only under Sections 2.3, 2.5,
         2.6, 2.7, 2.8; 2.9, 2.10, 2.11, 2.12, 2.13, 2.14 and 3.1(b) of this
         Amended and Restated Agreement, subject to the terms hereof.

16.      Notices. All notices to the Whitney Shareholders shall be delivered to
the following:

         c/o Whitney & Co.
         177 Broad Street
         Stamford, Connecticut  06901
         Attention:  Jeffrey R. Jay, M.D.

or such other address as the Whitney Shareholders may designate by ten (10) days
advance written notice to the other parties hereto.

17.      Requisite Approval. Upon execution and delivery of this Amendment by
the Company and Investors representing the requisite percentage of Registrable
Shares set forth in Section 6.5 of the Investors' Rights Agreement, this
Amendment shall constitute and be deemed to be an amendment to and part of the
Investors' Rights Agreement for all purposes.

18.      No Other Changes. Except as expressly set forth or contemplated in this
Amendment, the terms and conditions of the Investors' Rights Agreement shall
remain in place and shall not be altered, amended or changed in any manner
whatsoever, except by any further amendment to the Investors' Rights Agreement
made in accordance with the terms of the Investors' Rights Agreement, as hereby
amended.

19.      Counterparts. This Amendment may be executed in any number of
counterparts and by the different parties hereto on separate counterparts, each
of which when executed

                                       8
<PAGE>

and delivered shall be deemed an original effective for binding the parties
hereto, but all of which shall together constitute one and the same instrument.

20.      Governing Law. This Amendment shall be governed by and construed in
accordance with the laws of the State of California, without regard to the
principles of conflicts of law thereof.

                                       9
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have executed this Amendment No.
2 to the Amended and Restated Investors' Rights Agreement, and hereby consent to
the amendment and modification of the Investors' Rights Agreement provided
herein, as of the date first above written.

THE COMPANY:

SYMBION, INC.

By: /s/ Richard E. Francis, Jr.
    ----------------------------------------
Name: Richard E. Francis, Jr.
      --------------------------------------
Title: President and Chief Executive Officer
       -------------------------------------

INVESTORS:

UNIPHY PREFERRED SHAREHOLDERS:

ABS Capital Partners, L.P.

By: /s/ Frederick L. Bryant
    ----------------------------------------
Name: Frederick L. Bryant
     ---------------------------------------
Title:
       -------------------------------------

/s/ Clifford G. Adlerz
--------------------------------------------
Clifford G. Adlerz

--------------------------------------------
Randy W. Cook

--------------------------------------------
Paul Davis

/s/ Richard E. Francis, Jr.
--------------------------------------------
Richard E. Francis, Jr.

/s/ R. Dale Kennedy
--------------------------------------------
R. Dale Kennedy

                                       10
<PAGE>

--------------------------------------------
Tod Lambert

THE MARTIN COMPANIES, INC.

By: /s/ Charles N. Martin
    ----------------------------------------
Name: Charles N. Martin
     ---------------------------------------
Title:
      --------------------------------------

/s/ Kenneth C. Mitchell
--------------------------------------------
Kenneth C. Mitchell

Pacific Venture Group, L.P.
By:      PVG Equity Partner, L.L.C.,
         its General Partner

/s/ Eve M. Kurtin
--------------------------------------------
By: Eve M. Kurtin
Title: Member

PVG Associates, L.P.
By:      PVG Equity Partner, L.L.C.,
         its General Partner

/s/ Eve M. Kurtin
--------------------------------------------
By: Eve M. Kurtin
Title: Member

/s/ Patrick R. Rooney
--------------------------------------------
Patrick R. Rooney

/s/ Teresa F. Sparks
--------------------------------------------
Teresa F. Sparks

/s/ Gregg Stanley
--------------------------------------------
Gregg Stanley

/s/ Anthony Taparo
--------------------------------------------
Anthony Taparo

                                       11
<PAGE>

ARC KEY SHAREHOLDERS:

ARTHUR S. DEMOSS FOUNDATION

By:
    ----------------------------------------
Name:
     ---------------------------------------
Title:
      --------------------------------------

/s/ Jerry M. Eyler
--------------------------------------------
Jerry M. Eyler

FIRST AVENUE PARTNERS, L.P.

By:
    ----------------------------------------
Name:
     ---------------------------------------
Title:
      --------------------------------------

--------------------------------------------
William H. Freeman

--------------------------------------------
J. Michael Gould

HEALTH TECH AFFILIATES, INC.

By:
    ----------------------------------------
Name:
     ---------------------------------------
Title:
      --------------------------------------

HLM/CB Fund, L.P.

By:
    ----------------------------------------
Name:
     ---------------------------------------
Title:
      --------------------------------------

HLM Partners VII, L.P.

By:
    ----------------------------------------
Name:
     ---------------------------------------
Title:
      --------------------------------------

                                       12
<PAGE>

--------------------------------------------
W. Lawrence Hough

Piper Jaffray, Inc.

By:
    ----------------------------------------
Name:
     ---------------------------------------
Title:
      --------------------------------------

--------------------------------------------
B. Max Lauderdale

/s/ Charles N. Martin, Jr.
--------------------------------------------
Charles N. Martin, Jr.

/s/ Charles T. Neal
--------------------------------------------
Charles T. Neal

--------------------------------------------
Thomas Patten

--------------------------------------------
Keith B. Pitts

--------------------------------------------
Gary J. Prosterman

                                       13
<PAGE>

RICHLAND VENTURES II, L.P.

By:  /s/ Jack Tyrrell
     ---------------------------------------
Name:    Jack Tyrrell
Title:   Managing Partner

RICHLAND VENTURES III, L.P.

By:  /s/ Jack Tyrrell
     ---------------------------------------
Name:    Jack Tyrrell
Title:   Managing Partner

--------------------------------------------
Ann R. Schaaf

SOUTH ATLANTIC PRIVATE EQUITY FUND IV (QP),
LIMITED PARTNERSHIP

By: /s/ Donald W. Burton
    ----------------------------------------
Name: Donald W. Burton
     ---------------------------------------
Title: Managing Director
       -------------------------------------

SOUTH ATLANTIC PRIVATE EQUITY FUND IV, L.P.

By: /s/ Donald W. Burton
    ----------------------------------------
Name: Donald W. Burton
     ---------------------------------------
Title: Managing Director
       -------------------------------------

--------------------------------------------
Cal Turner, Jr.

/s/ William V.B. Webb
--------------------------------------------
William V.B. Webb

WW TWO, L.P.

By:
    ----------------------------------------
Name:
     ---------------------------------------
Title:
       -------------------------------------

--------------------------------------------
James A. Webb, III

                                       14
<PAGE>

WHITNEY SHAREHOLDERS:

J.H. WHITNEY III, L.P.

By:  J. H. Whitney Equity Partners III, L.L.C.,
         Its General Partner

By: /s/ Daniel J. O'Brien
    -------------------------------------------
Name: Daniel J. O'Brien
      -----------------------------------------
Title:   Managing Member
         --------------------------------------

J.H. WHITNEY IV, L.P.

By: J.H. Whitney Equity Partners IV, L.L.C.,
         Its General Partner

By:  /s/ Daniel J. O'Brien
     ------------------------------------------
Name: Daniel J. O'Brien
      -----------------------------------------
Title:   Managing Member
         --------------------------------------

WHITNEY STRATEGIC PARTNERS III, L.P.

By:  J. H. Whitney Equity Partners III, L.L.C.,
         Its General Partner

By:  /s/ Daniel J. O'Brien
     ------------------------------------------
Name: Daniel J. O'Brien
      -----------------------------------------
Title:   Managing Member
         --------------------------------------

UNIPHY FOUNDERS:

-----------------------------------------------
Peter Davidson

/s/ Shannon W. Fiser
-----------------------------------------------
Shannon W. Fiser

THE FRANCIS IRREVOCABLE TRUST, ANN FRANCIS,
TRUSTEE

By: /s/ Richard E. Francis, Jr.
    -------------------------------------------
Name: Richard E. Francis, Jr.
     ------------------------------------------
Title: Executor
       ----------------------------------------

                                       15
<PAGE>

--------------------------------------------
Victor Giovanetti

/s/ George M. Goodwin
--------------------------------------------
George M. Goodwin

--------------------------------------------
Marlene D. Kelley

/s/ H. Edward Kleine III
--------------------------------------------
H. Edward Kleine III

/s/ Darrell Naish
--------------------------------------------
Darrell Naish

/s/ Richard Panek
--------------------------------------------
Richard Panek

/s/ Vickie R. Warren
--------------------------------------------
Vickie R. Warren

PSC SHAREHOLDERS

/s/ Walter E. Schwing, Jr.
--------------------------------------------
Walter E. Schwing, Jr.

/s/ Robert Schwing
--------------------------------------------
Robert Schwing

                                       16
<PAGE>

ADDITIONAL UNIPHY PREFERRED SHAREHOLDERS:

--------------------------------------------
Bruce F. Chafin

--------------------------------------------
Ray Denson and Mary Denson, as joint tenants

--------------------------------------------
Ray Denson and Mary Denson, as Custodians
for Logan V. Denson

--------------------------------------------
Ray Denson and Mary Denson, as Custodians
for Morgan R. Denson

--------------------------------------------
Robert E. Galloway

--------------------------------------------
Stephen E. Hobbs

--------------------------------------------
Jeffrey W. Moore

--------------------------------------------
Joseph D. Moore

--------------------------------------------
Paul J. Moore

--------------------------------------------
Carol A. Murdock

--------------------------------------------
Phillip W. Roe

                                       17
<PAGE>

--------------------------------------------
Alan G. Thomas

--------------------------------------------
Daniel B. Soltman

--------------------------------------------
Ronald P. Soltman, as Custodian
for Sarah C. Soltman

--------------------------------------------
Ronald P. Soltman, as Custodian
for Joel M. Soltman

                                       18
<PAGE>

                                    EXHIBIT A

                              SCHEDULE OF INVESTORS

UNIPHY PREFERRED SHAREHOLDERS

ABS Capital Partners, L.P.*
Clifford G. Adlerz*
Bruce F. Chafin*
Randy W. Cook*
Paul Davis*
Ray Denson and Mary Denson, as joint tenants*
Ray Denson and Mary Denson, as Custodians for Logan V. Denson*
Ray Denson and Mary Denson, as Custodians for Morgan R. Denson*
Richard E. Francis, Jr.*
Robert E. Galloway*
Stephen E. Hobbs*
W. Lawrence Hough*
R. Dale Kennedy*
Tod Lambert
Kenneth C. Mitchell*
Jeffrey W. Moore*
Joseph D. Moore*
Paul J. Moore*
Carol A. Murdock*
Pacific Venture Group, L.P.*
Keith B. Pitts*
PVG Associates, L.P.*
Phillip W. Roe*
Patrick R. Rooney*
Teresa F. Sparks*
Gregg Stanley*
Anthony Taparo*
The Martin Companies, Inc.*
Alan G. Thomas*
Daniel B. Soltman*
Ronald P. Soltman, as Custodian for Sarah C. Soltman*
Ronald P. Soltman, as Custodian for Joel M. Soltman*
William V.B. Webb*

ARC KEY SHAREHOLDERS

Arthur S. Demoss Foundation*
Jerry M. Eyler*
First Avenue Partners, L.P.*
William H. Freeman
J. Michael Gould
Health Tech Affiliates, Inc.
HLM/CB Fund, L.P.*
HLM Partners VII, L.P.*
W. Lawrence Hough*

*   ANTI-DILUTION INVESTOR

                                       19
<PAGE>

Piper Jaffray, Inc.*
B. Max Lauderdale
Charles N. Martin, Jr.*
Charles T. Neal*
Thomas Patten
Keith B. Pitts*
Gary J. Prosterman
Richland Ventures II, L.P.*
Richland Ventures III, L.P.*
Ann R. Schaaf
South Atlantic Private Equity Fund IV (QP)*
South Atlantic Private Equity Fund
IV, L.P.*
Cal Turner, Jr.*
William V.B. Webb*
WW Two, L.P.*
James A. Webb, III

WHITNEY SHAREHOLDERS

J.H. Whitney III, L.P.*
J.H. Whitney IV, L.P.*
Whitney Strategic Partners III, L.P.*

UNIPHY FOUNDERS

Peter Davidson
Shannon W. Fiser
The Francis Irrevocable Trust, Ann Francis, Trustee*
Victor Giovanetti
George M. Goodwin
Marlene D. Kelley
H. Edward Kleine III
Darrell Naish
Richard Panek
Vickie R. Warren

PSC SHAREHOLDERS

Walter E. Schwing, Jr.
Robert Schwing

*  ANTI-DILUTION INVESTOR

                                       20<PAGE>
                                                                    EXHIBIT 4.10

NEITHER THIS SUBORDINATED CONVERTIBLE DEBENTURE NOR THE COMMON STOCK INTO WHICH
IT IS CONVERTIBLE HAVE BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR THE
SECURITIES LAWS OF ANY STATE AND NEITHER MAY BE SOLD NOR OTHERWISE TRANSFERRED,
EXCEPT AS OTHERWISE PROVIDED HEREIN, IN THE ABSENCE OF AN EFFECTIVE
REGISTRATION STATEMENT UNDER SUCH ACT OR AN OPINION OF COUNSEL REASONABLY
ACCEPTABLE TO THE ISSUER HEREOF THAT SUCH REGISTRATION IS NOT REQUIRED.

                     4% SUBORDINATED CONVERTIBLE DEBENTURE

                               DUE APRIL 1, 2005

$___________                      April 1, 2002            Nashville, Tennessee

         SYMBION, INC., a Tennessee corporation ("Symbion"), for value
received, hereby promises to pay to ____________________ (the "Holder") the
principal amount of _______________ ________________________ Dollars
($_________) (or so much thereof as shall not have been previously paid) plus
accrued and unpaid interest on April 1, 2005, or such earlier date provided
below. The unpaid principal of this Debenture remaining outstanding from time
to time shall bear interest at the rate of four percent (4%) per annum
(computed on the basis of a 365-day year) from the date hereof until payment of
all outstanding principal and interest hereunder or conversion of this
Debenture. Interest accrued hereunder shall be payable in arrears on April 1 of
each year, commencing April 1, 2003. Payments of principal and interest on this
Debenture shall be made to the Holder in lawful money of the United States of
America at the address of the Holder set forth in Section 6 hereof, or at such
other office or agency as the Holder shall have designated by written notice to
Symbion.

         Subject to the conversion right of the Holder set forth in Section 2,
Symbion shall have the right to prepay this Debenture in whole or in part,
without the prior written consent of the holder hereof, upon thirty (30) days
prior written notice to the Holder.

         This Debenture may not be transferred by the Holder, in whole or in
part.

1.       EVENTS OF DEFAULT. If any of the following conditions or events (each
an "Event of Default" and collectively, the "Events of Default") shall occur
and be continuing:

         (a)      if Symbion shall default in the payment of any principal on
                  this Debenture when same becomes due and payable and such
                  payment shall not have been made within thirty (30) days
                  after written notice of default shall have been received by
                  Symbion from the holder of this Debenture, except a default
                  in the payment of principal within thirty (30) days after
                  maturity, in which event no notice of default is required; or

         (b)      if Symbion shall default in the payment of any interest on
                  the Debenture when the same becomes due and payable and such
                  default shall continue more than thirty (30) days after
                  written notice of default shall have been received by Symbion
                  from the holder of this Debenture; or

<PAGE>

         (c)      if Symbion shall make an assignment for the benefit of
                  creditors, or shall admit in writing its inability to pay its
                  debts as they become due, or shall file a voluntary petition
                  in bankruptcy, or shall be adjudicated a bankrupt or
                  insolvent, or shall file any petition or answer seeking for
                  itself any reorganization, arrangement, composition,
                  readjustment, liquidation, dissolution or similar relief
                  under any current or future statute, law or regulation
                  relating to bankruptcy or insolvency, or shall file any
                  answer admitting or not contesting the material allegations
                  of a petition filed against Symbion in any such proceeding,
                  or shall seek or consent to or acquiesce in the appointment
                  of any custodian, trustee, receiver or liquidator of Symbion
                  or of all or any substantial part of the properties of
                  Symbion, or if Symbion or its Board of Directors shall take
                  any action looking to the dissolution or liquidation of
                  Symbion; or

         (d)      if, within sixty (60) days after the commencement of an
                  action against Symbion seeking any reorganization,
                  arrangement, composition, readjustment, liquidation,
                  dissolution or similar relief under any present or future
                  statute, law or regulation, such action shall not have been
                  dismissed or all orders or proceedings thereunder affecting
                  the operations or the business of Symbion stayed, or if the
                  stay of any such order or proceeding shall thereafter be set
                  aside, or if, within sixty (60) days after the appointment
                  without the consent or acquiescence of Symbion or any
                  custodian, trustee, receiver or liquidator of Symbion or of
                  all of any substantial part of the properties of Symbion,
                  such appointments, shall not have been vacated;

then, and in any such event, the holder hereof may at any time (unless all
defaults shall theretofore have been remedied) at its option, by written notice
to Symbion, declare this Debenture to be due and payable, whereupon this
Debenture shall forthwith mature and become due and payable, together with
interest accrued and unpaid hereon, without presentment, demand, protest or
notice, all of which are hereby waived.

2.       CONVERSION.

         2.1.     Conversion Right. Beginning on the date hereof and continuing
thereafter until this Debenture shall be paid in full or prepaid in full, as
the case may be, this Debenture may, at the election of the holder hereof upon
thirty (30) days prior written notice by the Holder hereof or ten (10) days
prior written notice given after a notice of prepayment given by Symbion as
described in the preamble hereto to Symbion of such election, be converted into
shares (the "Conversion Shares") of common stock, no par value, of Symbion (the
"Common Stock") at a price per share of $3.13 (the "Conversion Price"), subject
to adjustment as provided in Section 2.5 hereof.

         2.2      Manner of Conversion. This Debenture may be converted by the
holder hereof by presentment of this Debenture, accompanied by written election
stating that such holder elects to convert all of the principal amount thereof
and stating the name or names, together with addresses, in which the Conversion
Shares are to be issued. All of the principal amount must be tendered.
Conversion shall be deemed to have been affected immediately prior to the close
of business on the date on which this Debenture shall have been so surrendered
to Symbion; and at such time the rights of the holder as to the Debenture so
converted shall cease, and the person in whose name or names any certificate or
certificates for Conversion

                                       2
<PAGE>

Shares (or other securities) shall be issuable upon such conversion shall be
deemed to have become the holder or holders of record thereof.

         2.3      Automatic Conversion. This Debenture shall automatically be
converted, with no further action required to be taken by Symbion or the holder
hereof, upon the closing of an initial public offering (the "Initial Public
Offering") pursuant to an effective registration statement under the Securities
Act of 1933, as amended, covering the offer and sale of the capital stock of
Symbion, into the number of fully paid and non-assessable shares of Common
Stock equal to the quotient of (x) the unpaid principal amount of this
Debenture outstanding on the closing date of the Initial Public Offering
divided by (y) the Conversion Price then in effect (after giving effect to any
adjustments pursuant to Section 2.5 below). Immediately upon conversion as
provided herein, the holder shall be deemed to be the holder of record of the
Common Stock issuable upon conversion of this Debenture, notwithstanding that
the share register of Symbion shall then be closed or that certificates
representing the Common Stock shall not then actually be delivered to such
person. Upon written notice from Symbion, the holder of this Debenture so
converted shall promptly surrender this Debenture to Symbion at its principal
place of business to be maintained by it (or at such other office or agency of
Symbion as Symbion may designate by such notice to the holder).

         2.4.     Accrued Interest. Symbion will pay to the holder upon
conversion of this Debenture any accrued but unpaid interest in cash on the
principal amount so converted up to and including the date of conversion.

         2.5.     Adjustment of Conversion Price. The Conversion Price shall be
adjusted from time to time as follows:

                  2.5.1.   In case Symbion shall hereafter (i) pay a stock
dividend or make a stock distribution of shares of Common Stock with respect to
the Common Stock, (ii) subdivide its outstanding Common Stock into a greater
percentage of Common Stock, (iii) combine its outstanding Common Stock into a
smaller amount of Common Stock, or (iv) issue by reclassification of its Common
Stock any other security of Symbion, the Conversion Price in effect immediately
prior to such action shall be adjusted so that the holder of this Debenture or
any portion hereof thereafter surrendered for conversion shall be entitled to
receive the amount of Common Stock or other capital stock of Symbion which he
would have owned immediately following such action had this Debenture or any
remaining portion hereof been converted immediately prior thereto. All
adjustments made pursuant to this subsection 2.5.1 shall become effective
immediately after the record date in the case of a dividend or distribution and
shall become effective immediately after the effective date in the case of a
subdivision, combination or reclassification. If, as a result of an adjustment
made pursuant to this subsection 2.5.1, the holder of this Debenture or any
remaining portion hereof thereafter surrendered for conversion shall become
entitled to receive the Conversion Shares and other securities of Symbion, the
Board of Directors of Symbion shall reasonably and in good faith determine the
allocation of the adjusted Conversion Price between or among the Conversion
Shares and such other securities.

                  2.5.2.   If the amount of any single adjustment of the
Conversion Price required pursuant to subsection 2.5.1 would be less than one
cent ($.01) at the time such adjustment is otherwise so required to be made,
such amount shall be carried forward and adjustment with respect thereto made
at the time of and together with any subsequent adjustment

                                       3
<PAGE>

which, together with such amount and any other amount or amounts so carried
forward, shall aggregate at least one cent ($.01) when the Conversion Price is
adjusted.

         2.6.     Reservation of Common Stock Issuable on Conversion. Symbion
will at all times reserve and keep available, solely for issuance and delivery
upon the conversion of this Debenture, the amount of Common Stock, whether
authorized but unissued shares reserved by it which are free from preemptive
rights or issued shares which have been reacquired by it, from time to time
issuable upon the conversion of this Debenture at the time outstanding. Symbion
hereby covenants that all such securities shall be duly authorized and, when
issued upon such conversion, shall be validly issued and, in the case of
shares, fully paid and nonassessable with no liability on the part of the
holders thereof.

3.       SUBORDINATION.

         3.1.     Definition. For purposes of this Section 3.1 the term "Senior
Debt" shall mean any indebtedness for borrowed money, the payment of which
Symbion is at the time of determination responsible or liable as obligor,
guarantor or otherwise, other than (a) indebtedness as to which, in the
instrument creating or evidencing the same or pursuant to which the same is
outstanding, it is expressly provided that such indebtedness is junior and
subordinate to other indebtedness and obligations of Symbion, (b) indebtedness
which by its terms refers explicitly to this Debenture and states that such
indebtedness shall not be senior thereto and shall be equally subordinated and
equally junior, and (c) indebtedness of Symbion in respect of this Debenture.
Senior Debt shall continue to be Senior Debt and entitled to the benefits of
the subordination provisions set forth herein irrespective of any amendment,
modification, of waiver of any term of the Senior Debt or extension or renewal
of the Senior Debt.

         3.2.     Debenture Subordinate to Senior Debt. Symbion, for itself,
its successors and assigns, covenants and agrees, and each holder, by its
acceptance of this Debenture or any portion hereof, likewise covenants and
agrees, that this Debenture shall be subordinated and subject, to the extent
and in the manner herein set forth, in right of payment to the prior payment in
full of all Senior Debt. The provisions of this Section 3 are made for the
benefit of all holders of Senior Debt, and any such holder may proceed to
enforce such provisions.

         3.3.     Payment Over of Proceeds Upon Dissolution, Etc. No payment on
account of principal of (or premium, if any) or interest on this Debenture
shall be made, if any default or event of default with respect to any Senior
Debt, which permits or with the giving of notice or passage of time or both
would permit the holders thereof (or a trustee on their behalf) to accelerate
the maturity thereof, shall have occurred and be continuing and Symbion shall
have received written notice thereof from the holders of at least ten percent
(10%) in principal amount of any kind or category of any Senior Debt (or the
representative or representatives of such holders).

         In the event this Debenture is declared due and payable before the
maturity date hereof, or upon any payment or distribution of assets of Symbion
of any kind or character, whether in cash, property or securities, to creditors
upon any dissolution or winding-up or total or partial liquidation or
reorganization of Symbion, whether voluntary or paid in full or in bankruptcy,
insolvency, receivership or other proceedings, or upon any assignment by
Symbion for the benefit of creditors or any other marshalling of the assets of
Symbion, all principal of (and premium, if any) and interest due or to become
due upon all Senior Debt

                                       4
<PAGE>

(including any interest thereon occurring after the commencement of any such
proceeding) shall first be paid in full before the holder of this Debenture
shall be entitled to retain any assets so paid or distributed in respect of
this Debenture (for principal, premium, if any, or interest); and upon such
dissolution or winding-up or liquidation or reorganization or assignment or
marshalling of assets, any rights or distribution of assets, any payment or
distribution of assets of Symbion of any kind or character; whether in cash,
property or securities, to which the holders of this Debenture would be
entitled, except for the provisions of this Section, shall be paid by Symbion
or by any receiver, trustee in bankruptcy, liquidating trustee, agent or other
person making such payment or distribution, or by the holders of this Debenture
if received by them or it, directly to the holders of Senior Debt (pro rata to
each such holder as their interests may appear on the holders of the respective
amounts of Senior Debt held by such holder, including any interest thereon
accruing after the commencement of any such proceedings) or their
representatives, to the extent necessary to pay all Senior Debt in full, after
giving effect to any concurrent payment or distribution to or for the holders
of Senior Debt, before any payment or distribution is made to the holders of
this Debenture.

         No holder of Senior Debt shall be prejudiced in his right to enforce
subordination of this Debenture by any act or failure to act on the part of
Symbion.

         Subject to the payment in full of all Senior Debt, the holder of this
Debenture shall be subrogated (equally and ratably with the holders of all
indebtedness of Symbion which, by its express terms, ranks on a parity with
this Debenture and is entitled to like rights of subrogation) to the rights of
the holders of Senior Debt to receive payments or distributions of assets of
Symbion applicable to the Senior Debt until this Debenture shall be paid in
full. For purposes of such subrogation, no payments or distributions on the
Senior Debt pursuant to this Section shall, as between Symbion, its creditors
other than the holders of Senior Debt, and the holder of this Debenture, be
deemed to be a payment by Symbion to or on account of the Senior Debt, and no
payments or distributions to the holders of this Debenture of assets by virtue
of the subrogation herein provided for shall, as between Symbion, its creditors
other than the holder of Senior Debt, and the holders of this Debenture, be
deemed to be a payment to or on account of this Debenture. The provisions of
this Section are and are intended solely for the purpose of defining the
relative rights of the holder of this Debenture, on the one hand, and the
holders of Senior Debt, on the other hand, and nothing contained in this
Section or in this Debenture is intended to or shall impair the obligation of
Symbion, which is unconditional and absolute, to pay the principal of (and
premium, if any) and interest on this Debenture as and when the same shall
become due and payable in accordance with its terms, or to affect the relative
rights of the holders of this Debenture and creditors of Symbion other than the
holders of Senior Debt, nor shall anything herein prevent the holders of this
Debenture from exercising all remedies otherwise permitted by applicable law
upon default under this Debenture, subject to the rights, if any, under this
Section, of the holders of Senior Debt in respect of cash, property or
securities of Symbion otherwise payable or delivered to the holders of this
Debenture upon the exercise of any such remedy.

         Nothing contained in this Section 3.3 shall prevent conversion of this
Debenture.

4.       GOVERNING LAW. This Debenture shall be governed by the laws of the
State of Delaware.

                                       5
<PAGE>

5.       INTEREST RATE. Notwithstanding any other provision of this Debenture
or in any documents relating hereto, the holder of this Debenture shall not be
entitled to receive, collect, reserve or apply as interest, any amount in
excess of the maximum rate of interest permitted to be charged by applicable
law or regulations, as amended or enacted from time to time. In the event a
holder hereof ever receives, collects, reserves or applies as interest any such
excess, such amount which would be excessive interest shall be deemed a partial
prepayment of principal and treated hereunder as such or, if the principal
indebtedness evidenced hereby is paid in full, any remaining excess funds shall
immediately be paid to Symbion. In determining whether or not the interest paid
or payable, under any specific contingency, exceeds the maximum lawful rate of
interest, Symbion and the holder of this Debenture, to the maximum extent
permitted under applicable law, shall exclude voluntary prepayments and the
effects thereof; provided, that if the indebtedness is paid and performed in
full prior to maturity hereof, and if the interest received for the actual
period of existence hereof exceeds the maximum lawful rate of interest, the
holder hereof shall refund to Symbion the amount of such excess or credit the
amount of such excess against the principal portion of the indebtedness, as of
the date it was received and, in such event, the holder hereof shall not be
subject to any penalties payable to Symbion provided by any laws for
contracting for, charging, reserving or receiving interest in excess of the
maximum lawful rate of interest.

6.       NOTICES. All notices and communications required or permitted
hereunder shall be in writing and shall be sufficiently given and deemed to
have been received: (i) upon personal delivery or delivery by overnight
courier, (ii) when sent by facsimile or telecopier, with written confirmation
of receipt, or (iii) if mailed, upon the first to occur of actual receipt or
seventy-two (72) hours after being placed in the United States mail, postage
prepaid, registered or certified snail, receipt requested, in each case
addressed as follows:

         To the Holder at such address as the Holder has designated in writing
to Symbion.

         To Symbion:         Symbion, Inc.
                             3401 West End Avenue, Suite 760
                             Nashville, Tennessee 37203
                             Facsimile No.: (615) 386-6690
                             Attention: President

or such other address as a party may designate by notice to the other parties
hereto.

                    [The next page is the signature page.]

                                       6
<PAGE>

Executed April 1, 2002:

                                    SYMBION INC.

                                    By:
                                       ----------------------------------------
                                       Kenneth C. Mitchell
                                       Vice President

                                       7

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