<PAGE>

                                                                   EXHIBIT 10.12

                                 SYMBION, INC.,

                           THE GUARANTORS NAMED HEREIN

                                       AND

                           THE PURCHASERS NAMED HEREIN

                          SECURITIES PURCHASE AGREEMENT

                       Senior Subordinated Notes due 2008
                                of Symbion, Inc.

                            Dated as of July 18, 2003

<PAGE>

                                TABLE OF CONTENTS
                             (NOT PART OF AGREEMENT)

<TABLE>
<CAPTION>
                                                                                           Page
                                                                                           ----
<S>             <C>                                                                        <C>
PARAGRAPH 1.    AUTHORIZATION OF ISSUE OF SECURITIES..................................       1

PARAGRAPH 2.    PURCHASE AND SALE OF SECURITIES.......................................       1

PARAGRAPH 3.    CONDITIONS PRECEDENT..................................................       2

PARAGRAPH 4.    COVENANTS.............................................................       4

PARAGRAPH 5.    REPRESENTATIONS AND WARRANTIES........................................       5

PARAGRAPH 6.    ACKNOWLEDGEMENTS, REPRESENTATIONS AND AGREEMENT OF THE PURCHASERS.....       9

PARAGRAPH 7.    DEFINITIONS...........................................................      11

PARAGRAPH 8.    MISCELLANEOUS.........................................................      14
</TABLE>

<TABLE>
<CAPTION>
Exhibits
--------
<S>             <C>
Exhibit A       - Form of Note
Exhibit B-1     - Closing Documents
Exhibit B-2     - Form of Opinion of Counsel
Exhibit C       - Form of Investment Representation Letter
Exhibit D       - Form of Board Observation Rights Letter Agreement
</TABLE>

                                      -i-

<PAGE>

                                  SYMBION, INC.

                          SECURITIES PURCHASE AGREEMENT

Ladies and Gentlemen:

                  Each of the undersigned, SYMBION, INC., a Delaware corporation
(the "Company"), and the guarantors named on the signature pages hereto (the
"Guarantors" and, together with the Company, the "Issuers"), hereby agrees,
jointly and severally, with the parties named on the signature pages hereto
(collectively, the "Purchasers") as follows:

                  PARAGRAPH 1. AUTHORIZATION OF ISSUE OF SECURITIES.

                    1A. GENERAL. The 14 3/4% Senior Subordinated Notes of the
Company (including the Indenture attached thereto, the "Notes") are being issued
and sold (i) to refinance outstanding indebtedness of the Company and its
subsidiaries; (ii) to pay fees and expenses incurred in connection with the
issuance and sale of the Notes; and (iii) for general corporate purposes,
including acquisitions. Capitalized terms used herein and not otherwise defined
have the meanings specified in Paragraph 7.

                    1B. AUTHORIZATION OF NOTES. The Company has authorized the
issuance of the Notes in the aggregate initial principal amount of up to
$40,000,000, of which an aggregate initial principal amount of $15,106,000 will
be issued on the Initial Date of Closing, to be dated the date of issuance
thereof, to mature on July 18, 2008, and to be in the form of Exhibit A attached
hereto. The term "Notes" as used in this agreement (this "Agreement") shall
include the promissory notes delivered pursuant to this Agreement on each Date
of Closing, additional notes issued as pay-in-kind interest in lieu of cash
interest pursuant to the terms of the Notes and each such promissory note
delivered in substitution or exchange for any other Note pursuant to any such
provision hereof or of such Note.

                    1C. AUTHORIZATION OF GUARANTEES. In connection with the
issuance of the Notes, each of the Guarantors has authorized the issuance of its
unconditional senior subordinated guarantee of the Notes in the form of
Guarantee attached to Exhibit A hereto (the "Guarantees").

                  PARAGRAPH 2. PURCHASE AND SALE OF SECURITIES.

                    2A. PURCHASE OF SECURITIES. Subject to and upon the terms
and conditions herein set forth, the Issuers shall issue, sell and deliver to
each Purchaser, and each Purchaser agrees, severally and not jointly, to
purchase from the Issuers Securities (the "Initial Securities") as set forth on
the signature page hereto of such Purchaser, on the date designated

<PAGE>
                                      -2-

by the Company to the Purchasers no later than 1:00 p.m. (New York time) on such
date (the "Initial Date of Closing").

                    2B.    PURCHASE OF ADDITIONAL SECURITIES. In addition to the
Initial Securities to be issued and sold to the Purchasers on the Initial Date
of Closing, at any time prior to the second anniversary of the Initial Date of
Closing, the Company may, on one or more occasions (each such occasion, a
"Subsequent Date of Closing") and upon no less than five (5) nor more than
thirty (30) days' notice given to the Purchasers, draw down any remaining
Commitment (the "Additional Securities"); provided that on such Subsequent Date
of Closing (i) the Company is then able to incur at least $1.00 of additional
Indebtedness (other than Permitted Indebtedness) in compliance with Section 4.12
of the Indenture, including in such calculation the Additional Securities to be
purchased on such Subsequent Date of Closing; (ii) the aggregate principal
amount of Securities sold pursuant to this Agreement shall not exceed
$40,000,000; and (iii) the DLJ Purchasers (as defined herein) shall not be
requested to purchase less than $1,000,000 or integral multiples thereof on any
such date. The Securities purchased by the Purchasers on any such Subsequent
Date of Closing shall be allocated among the Purchasers on a pro rata basis
unless a Purchaser defaults on its obligation to purchase Additional Securities,
in which case the Securities shall be allocated among the non-defaulting
Purchasers on a pro rata basis provided that in no event shall any Purchaser be
obligated to purchase Securities in excess of its Commitment on such date.

                  PARAGRAPH 3. CONDITIONS PRECEDENT.

                  3.       CONDITIONS TO CLOSING. The obligation of each
Purchaser to purchase and pay for the Securities to be purchased by it is
subject to the satisfaction of the following conditions:

                    3A.    DOCUMENTS TO BE DELIVERED. The Purchasers shall have
received all of the following, duly executed and delivered:

                  (i)      On or before each Date of Closing, the Securities
         being purchased on such date by each Purchaser in the name and
         denomination set forth on the signature page hereto of such Purchaser;

                  (ii)     On or before the Initial Date of Closing, a copy of
         the Credit Agreement substantially in the form to be executed and
         delivered on or before the Initial Date of Closing;

                  (iii)    On or before the Initial Date of Closing,
         certificates of the Secretary, Assistant Secretary or other appropriate
         officer of the Issuers dated the Initial Date of Closing, which shall
         contain the names and signatures of the officers of each of the Issuers
         authorized to execute this Agreement and the Securities and which shall
         certify to the truth, correctness and completeness of the following
         exhibits attached hereto as

<PAGE>
                                      -3-

         Exhibit B-1: (a) a copy of resolutions duly adopted by the Board of
         Directors (or equivalent governing body) of each of the Issuers, in
         each case in full force and effect at the time this Agreement is
         entered into, authorizing the execution of this Agreement and the other
         Transaction Documents delivered or to be delivered in connection
         herewith on the part of the Issuers and the consummation of the
         transactions contemplated herein and therein, (b) a copy of the charter
         documents of each of the Issuers and all amendments thereto, certified
         by the appropriate official of the state of organization, and (c) a
         copy of the bylaws, limited partnership agreement, operating agreement
         or similar organizational documents of each of the Issuers in effect on
         the Initial Date of Closing;

                  (iv)     On or before the Initial Date of Closing, (A) a
         certificate (or certificates) as to the valid existence and good
         standing of each of the Issuers in its respective state of
         organization, issued by the appropriate authorities of such
         jurisdiction and (B) certificates of each of the Issuers' good standing
         and due qualification to do business, issued by appropriate officials
         in any states where such Issuer's ownership or leasing of its
         properties or the conduct of its business requires such qualification;

                  (v)      On or before the Initial Date of Closing, a favorable
         opinion of (a) Waller Lansden Dortch & Davis, PLLC, counsel to the
         Issuers, dated the Initial Date of Closing and substantially in the
         form set forth in Exhibit B-2, and (b) local counsel to the Issuers
         that are rendering opinions to the lenders under the Credit Agreement
         (which may be reliance letters) with respect to the valid existence and
         good standing of certain of the Issuers, in each case subject only to
         such qualifications, limitations or exceptions as may be reasonably
         acceptable to each of the Purchasers; and

                  (vi)     On or before each Date of Closing, a certificate of
         the Chief Executive Officer, President or Chief Financial Officer of
         the Company dated such Date of Closing, in which such officer certifies
         to the satisfaction of the conditions set out in subsections (i) and
         (ii) of Paragraph 3B and, with respect to each Subsequent Date of
         Closing, Paragraph 2B.

                    3B. REPRESENTATIONS; NO DEFAULT.

                  (i)      All representations and warranties made by the
         Issuers in this Agreement shall be true and correct on and as of each
         Date of Closing as if such representations and warranties had been made
         on and as of such date, unless such representation and warranty
         expressly indicates that it is being made as of any other specific date
         in which case on and as of such other date.

                  (ii)     The Issuers shall have performed and complied with
         all agreements and conditions required in this Agreement to be
         performed or complied with by them on or

<PAGE>
                                      -4-

         prior to such Date of Closing, and no Default or Event of Default has
         occurred and is continuing.

                    3C. PURCHASE PERMITTED BY APPLICABLE LAWS. On each Date of
Closing, the offer by the Issuers of, and the purchase of and payment for, the
Securities, on the terms and conditions herein provided (including the use of
the proceeds of the sale of the Securities by the Issuers) shall not violate any
applicable law or governmental regulation (including, without limitation,
Section 5 of the Securities Act or Regulation T, U or X of the Board of
Governors of the Federal Reserve System) and shall not subject any Purchaser to
any tax, penalty, liability or other onerous condition under or pursuant to any
applicable law or governmental regulation.

                    3D. PROCEEDINGS. On each Date of Closing, all corporate and
other proceedings taken or to be taken in connection with the transactions
contemplated hereby and all documents incident thereto shall be reasonably
satisfactory in substance and form to the Purchasers, and the Purchasers shall
have received all such counterpart originals or certified or other copies of
such documents as they may reasonably request.

                    3E. OBLIGATIONS. The Issuers shall have satisfied any other
obligations to the Purchasers required to be paid or complied with by them on or
prior to such Date of Closing.

                  PARAGRAPH 4. COVENANTS.

                  4.       COVENANTS. To induce the Purchasers to enter into
this Agreement and purchase the Securities, the Issuers, jointly and severally,
warrant, covenant and agree as follows:

                    4A. INDEMNITY. Each of the Issuers, jointly and severally,
agrees to indemnify each of the Purchasers, as debtholders, shareholders, board
observers, directors and/or officers of the Issuers, upon demand, from and
against any and all liabilities, obligations, claims, losses, damages,
penalties, actions, judgments, suits, costs, expenses or disbursements
(including reasonable fees of attorneys, accountants, experts and advisors) of
any kind or nature whatsoever (in this section collectively called "liabilities
and costs") which to any extent (in whole or in part) may be imposed on,
incurred by, or asserted against any of the Purchasers arising out of, resulting
from or in any other way associated with the execution, delivery or performance
of the Transaction Documents or such Purchaser's being a debtholder,
stockholder, board observer, director or officer of the Issuers but, with
respect to directors and officers, only to the extent permitted by such Issuer's
organizational documents and applicable state law. The foregoing indemnification
shall apply whether or not such liabilities and costs are in any way or to any
extent caused, in whole or in part, by any negligent act or omission of any kind
by such holder, provided only that no Purchaser shall be entitled under this
paragraph to receive indemnification for that portion, if any, of any

<PAGE>
                                      -5-

liabilities and costs which is proximately caused by such Purchaser's gross
negligence or willful misconduct. If any Person (including the Issuers or any of
their Affiliates) ever alleges such gross negligence or willful misconduct by a
Purchaser, the indemnification provided for in this Paragraph 4A shall
nonetheless be paid upon demand, subject to later adjustment or reimbursement,
until such time as a court of competent jurisdiction enters a final judgment as
to the extent and effect of the alleged gross negligence or willful misconduct.
For the avoidance of doubt, the Issuers acknowledge that they have determined
that no action be taken under the Company's Amended and Restated Investors'
Rights Agreement with respect to the sale of the Securities. As used in this
Paragraph 4A the term "Purchaser" shall refer also to each director, officer,
agent, attorney, employee, representative and Affiliate of such Purchaser.

                    4B. COMMITMENT FEE. So long as any Commitment is
available, the Company shall pay to each Purchaser a fee, payable in cash in
immediately available funds, semiannually on each January 15 and July 15,
commencing January 15, 2004, in the amount of 0.5% of the total Commitment of
such Purchaser at such date; provided that any Purchaser that defaults on its
obligation to purchase Additional Securities on a Subsequent Date of Closing
shall refund any fees received by it pursuant to this Paragraph 4B to the
Company since the immediately preceding Date of Closing; and provided, further,
that any Person that purchases Additional Securities on behalf of a defaulted
Purchaser shall be entitled to receive from the Company all commitment fees
related thereto since the immediately preceding Date of Closing. Nothing herein
shall be deemed to relieve any Purchaser from its obligation to fulfill its
Commitment or to prejudice or impair any rights (including any right of offset)
that the Company may have against any Purchaser as a result of any default by
such Purchaser.

                    4C. ADDITIONAL INFORMATION. The Issuers agree to furnish to
the Purchasers such documents, opinions, certificates and schedules or
instruments relating to the business, corporate, legal and financial affairs of
the Company and its subsidiaries as they shall reasonably request from time to
time.

                  PARAGRAPH 5. REPRESENTATIONS AND WARRANTIES.

                  5.       REPRESENTATIONS AND WARRANTIES. To induce the
Purchasers to enter into this Agreement and to purchase the Securities, the
Issuers, jointly and severally, represent and warrant as follows:

                    5A. ORGANIZATION AND GOOD STANDING. Each of the Company and
its Subsidiaries is duly organized, validly existing and in good standing under
the laws of its jurisdiction of incorporation, has the power and authority to
carry on its business as it is currently being conducted and to own, lease and
operate its properties, and is duly qualified and is in good standing as an
entity authorized to do business in each jurisdiction in which the nature of its
business or its ownership or leasing of property requires such qualification,

<PAGE>
                                      -6-

except where the failure to be so qualified, individually or in the aggregate,
could not reasonably be expected to result in a Material Adverse Effect.

                    5B. AUTHORIZATION. Each of the Issuers has taken all action
necessary to authorize the execution and delivery by it of each of this
Agreement and the other Transaction Documents to which it is a party and to
authorize the consummation of the transactions contemplated hereby and thereby
and the performance of its obligations hereunder and thereunder.

                    5C. NO CONFLICTS OR CONSENTS. The execution, delivery and
performance of the Transaction Documents, compliance by each of the Issuers with
all the provisions hereof and thereof (to which it is a party) and the
consummation of the transactions contemplated hereby and thereby will not
require any consent, approval, authorization or other order of any court,
regulatory body, administrative agency or other governmental body (except as
have been obtained prior to the Initial Date of Closing) and will not conflict
with or constitute a breach of any of the terms or provisions of, or a default
under, the charter or bylaws of the Company or any of its Subsidiaries or any
agreement, indenture or other instrument to which the Company or any of its
Subsidiaries is a party or by which the Company or any of its Subsidiaries or
their respective property is bound, or violate or conflict with any laws,
administrative regulations or rulings or court decrees applicable to the Company
or any of its Subsidiaries or their respective property, except to the extent
that any such violation or conflict could not reasonably be expected to have a
Material Adverse Effect.

                    5D. ENFORCEABLE OBLIGATIONS. Each of the Transaction
Documents constitutes a valid and legally binding agreement of each of the
Issuers (to which it is a party), enforceable against it in accordance with its
terms (assuming due authorization, execution and delivery of each Transaction
Document by any other party thereto), except that enforcement thereof may be
subject to (a) bankruptcy, insolvency, reorganization, moratorium or other
similar laws now or hereafter in effect relating to creditors' rights generally
and (b) general principles of equity (regardless of whether enforceability is
considered in a proceeding at law or in equity) and the discretion of any court
before which any proceeding therefor may be brought.

                    5E. NOTES. The Notes have been duly and validly authorized
by the Company and, when executed by the Company in accordance with the
provisions thereof, and delivered to and paid for by the Purchasers in
accordance with the terms hereof, will be entitled to the benefits thereof and
will constitute valid and binding obligations of the Company enforceable against
it in accordance with their terms, except that the enforcement thereof may be
subject to (a) bankruptcy, insolvency, reorganization, moratorium or other
similar laws now or hereafter in effect relating to creditors' rights generally
and (b) general principles of equity (regardless of whether enforceability is
considered in a proceeding at law

<PAGE>
                                      -7-

or in equity) and the discretion of any court before which any proceeding
therefor may be brought.

                    5F. GUARANTEES. The Guarantees have been duly and validly
authorized by each of the Guarantors and, when executed by each Guarantor and
affixed to the Notes, will be entitled to the benefits thereof and will
constitute valid and binding obligations of each such Guarantor enforceable
against it in accordance with their terms, except that the enforcement thereof
may be subject to (a) bankruptcy, insolvency, reorganization, moratorium or
other similar laws now or hereafter in effect relating to creditors' rights
generally and (b) general principles of equity (regardless of whether
enforceability is considered in a proceeding at law or in equity) and the
discretion of any court before which any proceeding therefor may be brought.

                    5G. NO CONFLICT. Neither the Company nor any of its
Subsidiaries is in violation of its respective organizational documents or in
default in the performance of any obligation, agreement or condition contained
in any bond, debenture, note or any other evidence of indebtedness or in any
other agreement, indenture or instrument material to the conduct of the business
of the Company and its Subsidiaries, taken as a whole, to which the Company or
any of its Subsidiaries is a party or by which the Company or any of its
Subsidiaries or property is bound except for such violations or defaults which,
individually or in the aggregate, could not reasonably be expected to result in
a Material Adverse Effect.

                    5H. FINANCIAL STATEMENTS.

                  (a)      The consolidated balance sheets of the Company and
its subsidiaries as of December 31 of each of 2000, 2001 and 2002 and the
related consolidated statements of income, shareholders' equity and cash flows
for each of the Fiscal Years then ended, including the opinions of Ernst & Young
LLP with respect thereto, together with the unaudited consolidating balance
sheets of the Company and its subsidiaries as of the end of such Fiscal Year and
the unaudited consolidating statements of income of the Company and its
subsidiaries for such Fiscal Year, copies of all of which have been furnished to
the Purchasers, are complete and correct and fairly present the assets,
liabilities and consolidated financial position of the Company and its
subsidiaries as at each such date and the consolidated results of their
operations and their cash flows for each of the Fiscal Years then ended.

                  (b)      The consolidated balance sheets of PSC and its
subsidiaries as of December 31 of each of 2000 and 2001 and the related
consolidated statements of income, shareholders' equity and cash flows for each
of the Fiscal Years then ended, including the opinions of Ernst & Young LLP with
respect thereto, together with the unaudited consolidating balance sheets of PSC
and its subsidiaries as of the end of such Fiscal Year and the unaudited
consolidating statements of income of PSC and its subsidiaries for such Fiscal
Year, copies of all of which have been furnished to the Purchasers, are complete
and correct and fairly present the assets, liabilities and consolidated
financial position of PSC and its

<PAGE>
                                      -8-

subsidiaries as at each such date and the consolidated results of their
operations and their cash flows for each of the Fiscal Years then ended.

                  (c)      The unaudited consolidated and consolidating balance
sheet of the Company and its subsidiaries as of March 31, 2003, together with
the related consolidated and consolidating statements of income and the related
consolidated statements of shareholders' equity and cash flows for the period
commencing at the beginning of the current Fiscal Year and ending with the end
of the Fiscal Quarter ended on such date, copies of all of which have been
furnished to the Purchasers, are complete and correct and, subject to customary
year-end adjustments that are not anticipated to be material, fairly present the
assets, liabilities and consolidated financial position of the Company and its
subsidiaries as at such date and the consolidated results of their operations
and their cash flows for such period.

                  (d)      the financial statements described in the preceding
Paragraphs 5H(a), (b) and (c), including the related schedules and notes
thereto, have been prepared in conformity with GAAP applied consistently
throughout the periods involved. Neither the Company nor any of its subsidiaries
has any material indebtedness, obligation or other unusual forward or long-term
commitment that is not fairly reflected in the foregoing financial statements or
in the notes thereto.

                  (e)      After giving effect to the consummation of the
transactions contemplated by this Agreement and the other Transaction Documents,
each of the Issuers is Solvent.

                    5I. NO UNDISCLOSED LIABILITIES. Except as fully reflected or
reserved against in the financial statements and the notes thereto referred to
in Paragraph 5H, there are no liabilities or obligations with respect to the
Company or any of its Subsidiaries of any nature whatsoever (whether absolute,
accrued, contingent or otherwise and whether or not due) which, either
individually or in the aggregate, would be material to the Company and its
Subsidiaries, taken as a whole. The Issuers do not know of any basis for the
assertion against the Company or any of its Subsidiaries of any liability or
obligation of any nature whatsoever that is not fully reflected in such
financial statements which, either individually or in the aggregate, could
reasonably be expected to result in a Material Adverse Effect.

                    5J. FULL DISCLOSURE. None of the Issuers is aware of any
fact that has not been disclosed to the Purchasers which, individually or in the
aggregate, could reasonably be expected to result in a Material Adverse Effect.

                    5K. INVESTMENT COMPANY. Neither the Company nor any of its
Subsidiaries is, or upon application of the proceeds from the sale of the
Securities will be, an "investment company" or a company "controlled" by an
"investment company" within the meaning of the Investment Company Act of 1940,
as amended.

<PAGE>
                                      -9-

                    5L. OFFERING OF SECURITIES. Except for solicitations to
offerees reasonably believed by the Issuers to be "accredited investors" as such
term is defined in Regulation D of the Securities Act, neither the Issuers nor
any agent acting on their behalf has, directly or indirectly, offered the
Securities or any similar security of the Issuers for sale to, or solicited any
offers to buy the Securities or any similar security of the Issuers from, any
Person other than the Purchasers, and neither the Issuers nor any agent acting
on their behalf has taken or will take any action which would subject the
issuance or sale of the Securities to the provisions of Section 5 of the
Securities Act or to the registration provisions of any securities or Blue Sky
law of any applicable jurisdiction in such a manner as to require that the
Securities actually be registered.

                    5M. USE OF PROCEEDS. Neither the Company nor any of its
Subsidiaries owns or has any present intention of acquiring any "margin stock"
as defined in Regulation U of the Board of Governors of the Federal Reserve
System ("margin stock"). The proceeds of sale of the Securities will be used as
set forth in Paragraph 1A. None of such proceeds will be used, directly or
indirectly, for the purpose, whether immediate, incidental or ultimate, of
purchasing or carrying any margin stock or for the purpose of maintaining,
reducing or retiring any indebtedness which was originally incurred to purchase
or carry any stock that is currently a margin stock or for any other purpose
which might constitute this transaction a "purpose credit" within the meaning of
such Regulation U. Neither the Company nor any agent acting on its behalf has
taken or will take any action which could reasonably be expected to cause this
Agreement or the Securities to violate Regulation T, Regulation U or any other
regulation of the Board of Governors of the Federal Reserve System or to violate
the Exchange Act, in each case as in effect now or as the same may hereafter be
in effect.

                    5N. OTHER REPRESENTATIONS AND WARRANTIES. The
representations and warranties contained in the Credit Agreement are true and
correct, except to the extent that a representation or warranty is made as of a
specific date, in which event such representation or warranty shall remain true
and correct as of such earlier date, and except to the extent that a
representation or warranty is no longer correct by virtue of changes in facts
and circumstances permitted by the terms of the Credit Agreement (as in effect
on the Initial Date of Closing), this Agreement or the Notes.

                  Any certificate signed by any officer of any Issuer pursuant
to this Agreement and delivered to any Purchaser or to counsel for the
Purchasers shall be deemed a representation and warranty by the Issuers to each
Purchaser as to the matters covered thereby.

                  PARAGRAPH 6. ACKNOWLEDGEMENTS, REPRESENTATIONS
                               AND AGREEMENT OF THE PURCHASERS.

                    6A. ACKNOWLEDGMENTS OF THE PURCHASERS. Each Purchaser
understands and acknowledges to the Issuers that:

<PAGE>
                                      -10-

                  (i)      the offering and sale of the Securities is intended
         to be exempt from registration under the Securities Act by virtue of
         the provisions of Section 4(2) of the Securities Act;

                  (ii)     there is no existing public or other market for the
         Securities and there can be no assurance that such Purchaser will be
         able to sell or dispose of such Purchaser's Securities;

                  (iii)    the Securities have not been registered under the
         Securities Act and must be held indefinitely unless they are
         subsequently registered under the Securities Act or such sale is
         permitted pursuant to an available exemption from such registration
         requirement;

                  (iv)     if any transfer of the Securities is to be made in
         reliance on an exemption under the Securities Act, the Issuers may
         require an opinion of counsel reasonably satisfactory to them that such
         transfer may be made pursuant to an exemption under the Securities Act;

                  (v)      the Securities may not be transferred without the
         written consent of the Company, which consent shall not be unreasonably
         withheld or delayed; and

                  (vi)     the Securities will have the legends contained on the
         forms thereof attached as exhibits hereto.

                    6B. REPRESENTATIONS OF THE PURCHASERS. Each Purchaser,
severally and not jointly, represents and warrants to the Issuers that:

                  (i)      the Securities to be acquired by it pursuant to this
         Agreement are being acquired for its own account, not as a nominee or
         agent for any other Person, and without a view to the distribution of
         such Securities or any interest therein in violation of the Securities
         Act;

                  (ii)     it is an "Accredited Investor" as such term is
         defined in Regulation D under the Securities Act and has such knowledge
         and experience in financial and business matters so as to be capable of
         evaluating the merits and risks of its investment in the Securities,
         and such Purchaser is capable of bearing the economic risks of such
         investment and is able to bear a complete loss of its investment in the
         Securities;

                  (iii)    it has been provided, to its satisfaction, the
         opportunity to ask questions concerning the terms and conditions of the
         offering and sale of the Securities, has had all such questions
         answered to its satisfaction and has been supplied all additional
         information as it has requested; and

<PAGE>
                                      -11-

                  (iv)     the execution, delivery, and performance of this
         Agreement is within such Purchaser's powers (corporate or otherwise)
         and has been duly authorized by all requisite action (corporate or
         otherwise).

                    6C. AGREEMENT OF THE DLJ PURCHASERS. The DLJ Purchasers
agree, for a period of thirty (30) days following the Initial Date of Closing,
to assign up to 15% of the Securities purchased by them on the Initial Date of
Closing (and a pro rata portion of the Commitment) to stockholders of the
Company or their designated affiliates who (1) are accredited investors, (2) are
entitled to nominate one or more members of the Board of Directors of the
Company pursuant to the terms of the Amended and Restated Voting Agreement,
dated as of June 25, 1999, as amended, by and among the Company and the
stockholders named therein, (3) beneficially own (together with such
stockholder's affiliates) shares of capital stock of the Company representing a
minimum of 3.0% of the outstanding shares of the Company's common stock
(assuming (a) conversion of all outstanding shares of the Company's Series A and
Series B convertible preferred stock and the Company's outstanding subordinated
convertible debentures and (b) exercise of all options held by such stockholder
which are exercisable), (4) are not executive officers of the Company and (5)
are designated by the Company; provided that (i) the purchase price shall be
100% of the principal amount together with interest accrued to the date of sale,
(ii) all transferees of Securities pursuant to this Section 6C shall execute and
deliver to the DLJ Purchasers and the Company a representation letter in the
form attached hereto as Exhibit C and such other documentation relating to such
assignments as reasonably required by (and in a form reasonably satisfactory to)
the DLJ Purchasers and the Company, and (iii) the Company shall pay the
reasonable out-of-pocket expenses of the DLJ Purchasers in connection with such
assignments.

                  PARAGRAPH 7. DEFINITIONS.

                  7.       Definitions. For the purpose of this Agreement,
capitalized terms used herein but not defined herein shall have the respective
meanings set forth in the Indenture. The following terms shall have the meanings
specified with respect thereto below (such meanings to be equally applicable to
both the singular and plural forms of the terms defined):

                  "ADDITIONAL SECURITIES" has the meaning set forth in Paragraph
2B.

                  "AGREEMENT" has the meaning set forth in Paragraph 1B.

                  "BOARD OBSERVATION RIGHTS LETTER AGREEMENT" means the board
observation rights letter agreement between the Company and DLJ Investment
Partners II, L.P., in the form of Exhibit D.

                  "COMMITMENT" means, as to any Purchaser at any time, the
aggregate principal amount of Notes such Purchaser is committed to purchase, as
set forth on the

<PAGE>
                                      -12-

signature page hereto of such Purchaser, less the aggregate principal amount of
Notes previously purchased by such Purchaser.

                  "COMPANY" has the meaning set forth in the introductory
paragraph to this Agreement.

                  "CREDIT AGREEMENT" means the credit agreement, dated as of
July 18, 2003, among the Company, Bank of America, N.A., as administrative agent
and issuing bank, and the other lenders party thereto, together with the
instruments, documents and agreements related thereto (including, without
limitation, any guarantee agreements and security documents), in each case as
such instruments, documents and agreements may be amended (including any
amendment and restatement thereof), supplemented or otherwise modified from time
to time, including any instrument, document or agreement extending the maturity
of, refinancing, replacing or otherwise restructuring all or any portion of the
indebtedness under such agreement or any successor or replacement agreement and
whether by the same or any other agent, lender or group of lenders.

                  "DATE OF CLOSING" means the Initial Date of Closing and any
Subsequent Date of Closing.

                  "DEFAULT" has the meaning set forth in Section 1.01 of the
Indenture.

                  "DLJ PURCHASERS" means DLJ Investment Partners II, L.P., DLJ
Investment Partners, L.P., DLJIP II Holdings, L.P., and their respective
successors and assigns permitted under this Agreement.

                  "EVENT OF DEFAULT" has the meaning set forth in Section 6.01
of the Indenture.

                  "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended.

                  "FISCAL QUARTER" means each of the accounting periods of
approximately three (3) months ending on March 31, June 30, September 30 and
December 31, respectively, of each year.

                  "FISCAL YEAR" means the twelve (12) month period ending on
December 31 of each year.

                  "GAAP" means generally accepted accounting principles set
forth in the opinions and pronouncements of the Accounting Principles Board of
the American Institute of Certified Public Accountants and statements and
pronouncements of the Financial Accounting Standards Board or in such other
statements by such other entity as approved by a significant segment of the
accounting profession of the United States, as amended or modified from time to
time.

<PAGE>
                                      -13-

                  "GUARANTEES" has the meaning set forth in Paragraph 1C.

                  "GUARANTORS" has the meaning set forth in the introductory
paragraph to this Agreement.

                  "HOLDER" means any holder of Securities from time to time.

                  "INDEBTEDNESS" has the meaning set forth in Section 1.01 of
the Indenture.

                  "INDENTURE" means the indenture attached as Exhibit A to the
Notes.

                  "INITIAL DATE OF CLOSING" has the meaning set forth in
Paragraph 2A.

                  "ISSUERS" has the meaning set forth in the introductory
paragraph to this Agreement.

                  "MATERIAL ADVERSE EFFECT" means a material adverse effect to
the business, condition (financial or otherwise), assets, liabilities, results
of operations or prospects of the Company and its subsidiaries, taken as a
whole, or the ability or obligation of the Issuers to perform on a timely basis
their obligations under this Agreement or the other Transaction Documents.

                  "NOTES" has the meaning set forth in Paragraph 1A.

                  "PERMITTED INDEBTEDNESS" has the meaning set forth in Section
1.01 of the Indenture.

                  "PERSON" means an individual, corporation, partnership,
limited partnership, limited liability company, limited liability limited
partnership, trust, business trust, association, joint stock company, joint
venture, pool, syndicate, sole proprietorship, unincorporated organization or
other form of entity not specifically listed herein.

                  "PSC" means Physicians Surgical Care, Inc., a Delaware
corporation that has become a subsidiary of the Company by virtue of merging
with a subsidiary of the Company and being the surviving corporation in the
merger.

                  "PURCHASERS" has the meaning set forth in the introductory
paragraph to this Agreement and shall include Transferees of such Persons.

                  "SECURITIES" means each of the Notes and the Guarantees.

                  "SECURITIES ACT" means the Securities Act of 1933, as amended.

<PAGE>
                                      -14-

                  "SOLVENT" means, with respect to any Person on any particular
date, that on such date (a) the fair value of the assets of such Person (both at
fair valuation and at present fair saleable value) is, on the date of
determination, greater than the total amount of liabilities, including
contingent and unliquidated liabilities, of such Person, (b) such Person is able
to pay all contingent and unliquidated liabilities of such Person as they
mature, and (c) such Person does not have unreasonably small capital with which
to carry on its business. In computing the amount of contingent or unliquidated
liabilities at any time, such liabilities will be computed at the amount that,
in light of all the facts and circumstances existing at the time, represents the
amount that can be reasonably expected to become an actual or mature liability.

                  "SUBSEQUENT DATE OF CLOSING" has the meaning set forth in
Paragraph 2B.

                  "TRANSACTION DOCUMENTS" means this Agreement, the Notes, the
Guarantees, the Management Rights Letter Agreement and all other agreements,
certificates, documents, instruments and writings at any time delivered in
connection herewith or therewith.

                  "TRANSFEREE" means any direct or indirect transferee of all or
any part of any Security purchased under this Agreement.

                    7A. TERMS AND DETERMINATIONS. Unless otherwise specified
herein, all accounting terms used herein shall be interpreted, all
determinations with respect to accounting matters hereunder shall be made, and
all unaudited financial statements and certificates and reports as to financial
matters required to be furnished hereunder shall be prepared in accordance with
GAAP.

                  PARAGRAPH 8. MISCELLANEOUS.

                  8.       MISCELLANEOUS.

                    8A. EXPENSES. The Issuers, jointly and severally, agree,
whether or not the transactions contemplated hereby or the other Transaction
Documents shall be consummated, to pay, and save the Purchasers and any
Transferee harmless against liability for the payment of, all reasonable
out-of-pocket expenses arising in connection with such transactions promptly
(and, in any event, within 30 days after any invoice or other statement or
notice), including (i) all reasonable fees and expenses of Cahill Gordon &
Reindel LLP, special counsel to the Purchasers, in connection with this
Agreement, the other Transaction Documents and the transactions contemplated
hereby and thereby, (ii) all document production and duplication charges and the
reasonable fees and expenses of counsel engaged by the Purchasers or such
Transferees in connection with any subsequent proposed modification of, or
proposed consent under, this Agreement or the other Transaction Documents
whether or not such proposed modification shall be effected or proposed consent
granted, and (iii) the costs and expenses, including reasonable attorneys' fees,
incurred by the Purchasers or such Transferee in enforcing (or determining
whether or how to enforce) any

<PAGE>
                                      -15-

rights under this Agreement or the other Transaction Documents or in responding
to any subpoena or other legal process or informal investigative demand issued
in connection with this Agreement, the other Transaction Documents or the
transactions contemplated hereby or thereby or by reason of the Purchasers' or
such Transferee's having acquired any Security, including without limitation
costs and expenses incurred in any bankruptcy case. The obligations of the
Issuers under this Paragraph 8A shall survive the transfer of any Security or
portion thereof or interest therein by any Purchaser or any Transferee, and the
payment of any Security.

                    8B. CONSENT TO AMENDMENTS. Except as otherwise expressly
provided herein, the provisions of this Agreement may be amended and an Issuer
may take any action herein prohibited, or omit to perform any act herein
required to be performed by it, only if such Issuer has obtained the written
consent of Holders of a majority in principal amount of the Securities then
outstanding, or, if prior to the Initial Date of Closing, all of the Purchasers.

                    8C. SURVIVAL OF REPRESENTATIONS AND WARRANTIES; ENTIRE
AGREEMENT. All representations and warranties contained herein or made in
writing by or on behalf of the Issuers in connection herewith shall survive the
execution and delivery of this Agreement, the Securities, the transfer by any
Purchaser of any Security or portion thereof or interest therein, the payment of
any Security, and may be relied upon by any Transferee, regardless of any
investigation made at any time by or on behalf of any Purchaser or any
Transferee. Subject to the preceding sentence, this Agreement and the other
Transaction Documents embody the entire agreement and understanding between each
Purchaser and the Issuers and supersede all prior agreements and understandings
relating to the subject matter hereof.

                    8D. SUCCESSORS AND ASSIGNS. All covenants and other
agreements in this Agreement contained by or on behalf of any of the parties
hereto shall bind and inure to the benefit of the respective successors and
permitted assigns of the parties hereto (including, without limitation, any
Transferee) whether so expressed or not; provided that no Purchaser may transfer
Securities, other than to an affiliate of such Purchaser, without the written
consent of the Company, which consent shall not be unreasonably withheld or
delayed.

                    8E. NOTICES. All notices or other communications provided
for hereunder shall be in writing and sent by telecopy or nationwide overnight
delivery service (with charges prepaid) and (i) if to any Purchaser, addressed
to it at the address specified for such communications on the signature pages
hereof, or at such other address as such Purchaser shall have specified to the
Company in writing, (ii) if to any other Holder, addressed to such other Holder
at such address as such other Holder shall have specified to the Company in
writing or, if any such other Holder shall not have so specified an address to
the Company, then addressed to such other Holder in care of the last Holder
which shall have so specified an address to the Company and (iii) if to the
Issuers, addressed to the Company at 40 Burton Hills Boulevard, Suite 500,
Nashville, Tennessee 37215, Attention: Chief Financial Officer,

<PAGE>
                                      -16-

or at such other address as the Company shall have specified to the Holder of
each Security in writing.

                    8F. GOVERNING LAW. THIS AGREEMENT SHALL BE CONSTRUED AND
ENFORCED IN ACCORDANCE WITH, AND THE RIGHTS OF THE PARTIES SHALL BE GOVERNED BY,
THE LAW OF THE STATE OF NEW YORK WITHOUT REGARD TO PRINCIPLES OF CONFLICT OF
LAWS (OTHER THAN NEW YORK GENERAL OBLIGATIONS LAW Section 5-1401). Any legal
action or proceeding with respect to this Agreement or any other Transaction
Document may be brought in the courts of the State of New York or of the United
States for the Southern District of New York, and, by execution and delivery of
this Agreement, each of the Issuers hereby irrevocably accepts for itself and in
respect of its property, generally and unconditionally, the non-exclusive
jurisdiction of the aforesaid courts. Each of the Issuers further irrevocably
consents to the service of process out of any of the aforementioned courts in
any such action or proceeding by the mailing of copies thereof by registered or
certified mail, postage prepaid, to it at its address for notices pursuant to
Paragraph 8E, such service to become effective five (5) days after such mailing.
Nothing herein shall affect the right of any Holder to serve process in any
other manner permitted by law or to commence legal proceedings or otherwise
proceed against the Company in any other jurisdiction. Each of the Issuers
hereby irrevocably waives any objection which it may now or hereafter have to
the laying of venue of any of the aforesaid actions or proceedings arising out
of or in connection with this Agreement or any other Transaction Document
brought in the courts referred to above and hereby further irrevocably waives
and agrees not to plead or claim in any such court that any such action or
proceeding brought in any such court has been brought in an inconvenient forum.

                    8G. SEVERABILITY. Any provision of this Agreement 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, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

                    8H. DESCRIPTIVE HEADINGS. The descriptive headings of the
several paragraphs of this Agreement are inserted for convenience only and do
not constitute a part of this Agreement.

                    8I. COUNTERPARTS. This Agreement may be executed in any
number of counterparts, each of which shall be an original but all of which
together shall constitute one instrument.

<PAGE>

                  If you are in agreement with the foregoing, please sign the
form of acceptance on the enclosed counterpart of this letter and return the
same to the Company whereupon this letter shall become a binding agreement by
and among the Issuers and each of you.

                                              Very truly yours,

                                              SYMBION, INC.

                                              By: /s/ Kenneth C. Mitchell
                                                  ------------------------------
                                                  Name:  Kenneth C. Mitchell
                                                  Title: Chief Financial Officer

                                              GUARANTORS:

                                              AMBULATORY RESOURCE CENTRES
                                              INVESTMENT COMPANY, INC.

                                              AMBULATORY RESOURCE CENTRES OF
                                              FLORIDA, INC.

                                              AMBULATORY RESOURCE CENTRES OF
                                              MASSACHUSETTS, INC.

                                              AMBULATORY RESOURCE CENTRES OF
                                              TEXAS, INC.

                                              AMBULATORY RESOURCE CENTRES OF
                                              WASHINGTON, INC.

                                              AMBULATORY RESOURCE CENTRES OF
                                              WILMINGTON, INC.

                                              ARC DEVELOPMENT CORPORATION

                                              ARC DRY CREEK, INC.

                                              ARC FINANCIAL SERVICES CORPORATION

<PAGE>

                                              HOUSTON PSC - I, INC.

                                              LUBBOCK SURGICENTER, INC.

                                              PHYSICIANS SURGICAL CARE, INC.

                                              PHYSICIANS SURGICAL CARE
                                              MANAGEMENT, INC.

                                              SARC/ASHEVILLE, INC.

                                              SARC/CIRCLEVILLE, INC.

                                              SARC/DELAND, INC.

                                              SARC/FT. MYERS, INC.

                                              SARC/FW, INC.

                                              SARC/JACKSONVILLE, INC.

                                              SARC/KNOXVILLE, INC.

                                              SARC/LARGO, INC.

                                              SARC/LARGO ENDOSCOPY, INC.

                                              SARC/METAIRIE, INC.

                                              SARC/VINCENNES, INC.

                                              SARC/WORCESTER, INC.

                                              SI/DRY CREEK, INC.

                                              SURGICARE OF DELAND, INC.

                                              SYMBION AMBULATORY RESOURCE
                                              CENTRES, INC.

                                              SYMBIONARC MANAGEMENT SERVICES,
                                              INC.

<PAGE>

                                              SYMBION IMAGING, INC.

                                              TEXARKANA SURGERY CENTER GP, INC.

                                              UNIPHY HEALTHCARE OF JOHNSON CITY
                                              VI, INC.

                                              UNIPHY HEALTHCARE OF LOUISVILLE,
                                              INC.

                                              UNIPHY HEALTHCARE OF MEMPHIS I,
                                              INC.

                                              UNIPHY HEALTHCARE OF MEMPHIS III,
                                              INC.

                                              UNIPHY HEALTHCARE OF MEMPHIS IV,
                                              INC.

                                              VILLAGE SURGICENTER, INC.

                                              By: /s/ Kenneth C. Mitchell
                                                  ------------------------------
                                                  Name:  Kenneth C. Mitchell
                                                  Title: Vice President

                                              ARC OF BELLINGHAM, L.P.

                                              By: AMBULATORY RESOURCE CENTRES
                                                  OF WASHINGTON, INC.,
                                                  its General Partner

                                                  By:  /s/ Kenneth C. Mitchell
                                                      --------------------------
                                                      Name:  Kenneth C. Mitchell
                                                      Title: Vice President

<PAGE>

                                              WILMINGTON SURGERY CENTER, LP

                                              By: AMBULATORY RESOURCE
                                                  CENTRES OF WILMINGTON, INC.,
                                                  its General Partner

                                                  By: /s/ Kenneth C. Mitchell
                                                      ----------------------
                                                      Name:  Kenneth C. Mitchell
                                                      Title: Vice President

                                              PSC DEVELOPMENT COMPANY, LLC

                                              PSC OF NEW YORK, L.L.C.

                                              PSC OPERATING COMPANY, LLC

                                              SARC/SAN ANTONIO, LLC

                                              SARC/WEST HOUSTON, LLC

                                              By: /s/ Kenneth C. Mitchell
                                                  ------------------------------
                                                  Name: Kenneth C. Mitchell
                                                  Title: Vice President

<PAGE>

                      SIGNATURE PAGE TO PURCHASE AGREEMENT

Accepted and Agreed as of the
date first above written:

DLJ INVESTMENT PARTNERS II, L.P.

By: DLJ INVESTMENT PARTNERS II, INC.,      Commitment: $22,731,000.00
    as managing general partner

By: /s/ Mike Isikon                        Principal Amount of Notes To Be
    -----------------------                Purchased on Initial Date of Closing:
    Name: Mike Isikon                      $8,584,000.00
    Title: Auth. Sig.

Address of Purchaser:

Mr. Doug Ladden
DLJ Investment Partners
Eleven Madison Avenue
New York, NY 10010

Telecopy No.: (212) 538-0422

Designated Bank: Citibank, N.A.

ABA Number: 021-000-089

Address: New York, NY

Account No.: 30537554

Attention: Ruchi Pinniger

Taxpayer I.D. Number: 13-4048184
(if registered in the name of a
nominee, the nominee Taxpayer
I.D. Number)

Nominee (name in which Securities are to be registered, if different than name
of Purchaser)

<PAGE>

                      SIGNATURE PAGE TO PURCHASE AGREEMENT

Accepted and Agreed as of the
date first above written:

DLJ INVESTMENT PARTNERS, L.P.

By: DLJ INVESTMENT PARTNERS II, INC.,      Commitment: $10,102,000.00
    as managing general partner

By: /s/ Mike Isikon                        Principal Amount of Notes To Be
    -----------------------                Purchased on Initial Date of Closing:
    Name: Mike Isikon                      $3,815,000.00
    Title: Auth. Sig.

Address of Purchaser:

Mr. Doug Ladden
DLJ Investment Partners
Eleven Madison Avenue
New York, NY 10010

Telecopy No.: (212) 538-0422

Designated Bank: Citibank, N.A.

ABA Number: 021-000-089

Address: New York, NY

Account No.: 30537562

Attention: Ruchi Pinniger

Taxpayer I.D. Number: 13-3868693
(if registered in the name of a
nominee, the nominee Taxpayer
I.D. Number)

Nominee (name in which Securities are to be registered, if different than name
of Purchaser)

____________________
<PAGE>

                      SIGNATURE PAGE TO PURCHASE AGREEMENT

Accepted and Agreed as of the
date first above written:

DLJIP II HOLDINGS, L.P.

By: DLJ INVESTMENT PARTNERS II, INC.,      Commitment: $7,167,000.00
    as managing general partner

By: /s/ Mike Isikon                        Principal Amount of Notes To Be
    -----------------------                Purchased on Initial Date of Closing:
    Name: Mike Isikon                      $2,707,000.00
    Title: Auth. Sig.

Address of Purchaser:

Mr. Doug Ladden
DLJ Investment Partners
Eleven Madison Avenue
New York, NY 10010

Telecopy No.: (212) 538-0422

Designated Bank: Citibank, N.A.

ABA Number: 021-000-089

Address: New York, NY

Account No.: 30537589

Attention: Ruchi Pinniger

Taxpayer I.D. Number: 13-4192504
(if registered in the name of a
nominee, the nominee Taxpayer
I.D. Number)

Nominee (name in which Securities are to be registered, if different than name
of Purchaser)

____________________