<PAGE>
                                                                   EXHIBIT 10.19
 
                                6,000,000 Shares

                         AMERISOURCE HEALTH CORPORATION

                                  Common Stock


                             UNDERWRITING AGREEMENT
                             ----------------------


                                                                February 4, 1999


DONALDSON, LUFKIN & JENRETTE
  SECURITIES CORPORATION
SALOMON SMITH BARNEY INC.
J.P. MORGAN SECURITIES INC.
FIRST UNION CAPITAL MARKETS CORP.
MCDONALD INVESTMENTS INC.
PIPER JAFFRAY INC.
  c/o Donaldson, Lufkin & Jenrette Securities Corporation
  277 Park Avenue
  New York, New York  10172

Dear Sirs:

          Certain stockholders of AmeriSource Health Corporation, a Delaware
corporation (the "Company"), named in Schedule II hereto (the "Selling
Stockholders") severally propose to sell to you hereto (the "Underwriters"), an
aggregate of 6,000,000 shares of the Class A Common Stock, par value $.01 per
share of the Company (the "Shares"), each Selling Stockholder selling the amount
set forth opposite such Selling Stockholder's name in Schedule II hereto.  The
shares of common stock of the Company to be outstanding after giving effect to
the sales contemplated hereby are hereinafter referred to as the "Common Stock".

          SECTION 1.  Registration Statement and Prospectus.  The Company has
                      -------------------------------------                  
prepared and filed with the Securities and Exchange Commission (the
"Commission")  in accordance with the provisions of the Securities Act of 1933,
as amended, and the rules and regulations of the Commission thereunder
(collectively, the "Act"), a registration statement on Form S-3, in-
<PAGE>
 
                                      -2-


cluding a prospectus, relating to the Shares. The registration statement, as
amended at the time it became effective, including the information (if any)
deemed to be part of the registration statement at the time of effectiveness
pursuant to Rule 430A under the Act, is hereinafter referred to as the
"Registration Statement"; and the prospectus in the form first used to confirm
sales of Shares is hereinafter referred to as the "Prospectus" (including, in
the case of all references to the Registration Statement or the Prospectus,
documents incorporated therein by reference).

          The terms "supplement" and "amendment" or "amend" as used in this
Agreement with respect to the Registration Statement or the Prospectus shall
include all documents subsequently filed by the Company with the Commission
pursuant to the Securities Exchange Act of 1934, as amended, and the rules and
regulations of the Commission thereunder (collectively, the "Exchange Act") that
are deemed to be incorporated by reference in the Prospectus.

          SECTION 2.  Agreements to Sell and Purchase and Loc-Up Agreements.  On
                      -----------------------------------------------------     
the basis of the representations and warranties contained in this Agreement, and
subject to its terms and conditions, each Selling Stockholder agrees, severally
and not jointly, to sell the number of Shares set forth opposite such Selling
Stockholder's name in Schedule II hereto and each Underwriter agrees, severally
and not jointly, to purchase from each Selling Stockholder at a price per Share
of $73.63 (the "Purchase Price") the number of Shares (subject to such
adjustments to eliminate fractional shares as you may determine) that bears the
same proportion to the total number of Shares to be sold by such Selling
Stockholder as the number of Shares set forth opposite the name of such
Underwriter in Schedule I hereto bears to the total number of Shares.

          The Company and each Selling Stockholder hereby agrees not to (i)
offer, pledge, sell, contract to sell, sell any option or contract to purchase,
purchase any option or contract to sell, grant any option, right or warrant to
purchase, or otherwise transfer or dispose of, directly or indirectly, any
shares of Common Stock or any securities convertible into or exercisable or
exchangeable for Common Stock or (ii) enter into any swap or other arrangement
that transfers all or a portion of the economic consequences associated with the
ownership of any Common Stock (regardless of whether any of the transactions
described in clause (i) or (ii) is to be settled by the delivery of Common
Stock, or such other securities, in cash or 
<PAGE>
 
                                      -3-

otherwise), except to the Underwriters pursuant to this Agreement, for a period
of 90 days after the date of the Prospectus without the prior written consent of
Donaldson, Lufkin & Jenrette Securities Corporation. Notwithstanding the
foregoing, during such period (A) the Company (i) may grant stock options
pursuant to the Company's stock option plans and (ii) may issue shares of Common
Stock upon the exercise of an option or warrant or the conversion of a security
outstanding on the date hereof and (B) each Selling Stockholder may engage in
any of such transactions pursuant to transfers to affiliated entities. The
Company also agrees not to file any registration statement with respect to any
shares of Common Stock or any securities convertible into or exercisable or
exchangeable for Common Stock for a period of 90 days after the date of the
Prospectus without the prior written consent of Donaldson, Lufkin & Jenrette
Securities Corporation, except for registration statements on Form S-8 or S-3
relating to securities issued in connection with employee benefit plans. In
addition, each Selling Stockholder agrees that, for a period of 90 days after
the date of the Prospectus without the prior written consent of Donaldson,
Lufkin & Jenrette Securities Corporation, it will not make any demand for, or
exercise any right with respect to, the registration of any shares of Common
Stock or any securities convertible into or exercisable or exchangeable for
Common Stock. Except as disclosed in the Prospectus, the Company shall, prior to
or concurrently with the execution of this Agreement, deliver an agreement
executed by certain directors and each of its executive officers of the Company
to the effect that such person will not, during the period commencing on the
date such person signs such agreement and ending 90 days after the date of the
Prospectus, without the prior written consent of Donaldson, Lufkin & Jenrette
Corporation, (A) engage in any of the transactions described in the first
sentence of this paragraph or (B) make any demand for, or exercise any right
with respect to, the registration of any shares of Common Stock or any
securities convertible into or exercisable or exchangeable for Common Stock; 
provided, however, that this shall not apply to sales in private transactions 
--------  -------                              
(i.e., transactions not involving a public sale, public distribution or other 
 ---                                            
public disposition of shares of capital stock of the Company, nor any sale
pursuant to Rule 144A promulgated under the Act).

          SECTION 3.  Terms of Public Offering.  The Company and Selling
                      ------------------------                          
Stockholders are advised by you that the Underwriters propose (i) to make a
public offering of their respective portions of the Shares as soon after the
execution and delivery of this Agreement as in your judgment is advisable and
<PAGE>
 
                                      -4-

(ii) initially to offer the Shares upon the terms set forth in the Prospectus.

          SECTION 4.  Delivery and Payment.  The Shares shall be represented by
                      --------------------                                     
definitive certificates and shall be issued in such authorized denominations and
registered in such names as Donaldson, Lufkin & Jenrette Securities Corporation
shall request no later than two business days prior to the Closing Date.  The
Shares shall be delivered by or on behalf of the Selling Stockholders, with any
transfer taxes thereon duly paid by the respective Selling Stockholders, to
Donaldson, Lufkin & Jenrette Securities Corporation through the facilities of
The Depository Trust Company ("DTC"), for the respective accounts of the several
Underwriters, against payment to the Selling Stockholders of the Purchase Price
therefore by wire transfer of Federal or other funds immediately available in
New York City.  The certificates representing the Shares shall be made available
for inspection not later than 9:30 A.M., New York City time, on the business day
prior to the Closing Date, at the office of DTC or its designated custodian (the
"Designated Office").  The time and date of delivery and payment for the Shares
shall be 9:00 A.M., New York City time, on February 10, 1999 or such other time
on the same or such other date as Donaldson, Lufkin & Jenrette Securities
Corporation and the Company shall agree in writing.  The time and date of
delivery and payment for the Firm Shares are hereinafter referred to as the
"Closing Date".

          The documents to be delivered on the Closing Date on behalf of the
parties hereto pursuant to Section 9 of this Agreement shall be delivered at the
offices of Cahill Gordon & Reindel, 80 Pine Street, New York, NY 10005 and the
Shares shall be delivered at the Designated Office, all on the Closing Date.

          SECTION 5.  Agreements of the Company.  The Company agrees with you:
                      -------------------------                               

          (a)  To advise you promptly and, if requested by you, to confirm such
     advice in writing, (i) of any request by the Commission for amendments to
     the Registration Statement or amendments or supplements to the Prospectus
     or for additional information, (ii) of the issuance by the Commission of
     any stop order suspending the effectiveness of the Registration Statement
     or of the suspension of qualification of the Shares for offering or sale in
     any jurisdiction, or the initiation of any proceeding for such pur-
<PAGE>
 
                                      -5-

     poses, (iii) when any amendment to the Registration Statement becomes
     effective, (iv) if the Company files a Rule 462(b) Registration Statement
     after the effectiveness of this Agreement, when the Rule 462(b)
     Registration Statement has become effective and (v) of the happening of any
     event during the period referred to in Section 5(d) below which makes any
     statement of a material fact made in the Registration Statement or the
     Prospectus untrue or which requires any additions to or changes in the
     Registration Statement or the Prospectus in order to make the statements
     therein not misleading. If at any time the Commission shall issue any stop
     order suspending the effectiveness of the Registration Statement, the
     Company will make every reasonable effort to obtain the withdrawal or
     lifting of such order at the earliest possible time.

          (b)  To furnish to you 3 signed copies of the Registration Statement
     as first filed with the Commission and of each amendment to it, including
     all exhibits and documents incorporated therein by reference, and to
     furnish to you and each Underwriter designated by you such number of
     conformed copies of the Registration Statement as so filed and of each
     amendment to it, without exhibits but including documents incorporated
     therein by reference, as you may reasonably request.

          (c)  To prepare the Prospectus, the form and substance of which shall
     be reasonably satisfactory to you,  and to file the Prospectus in such form
     with the Commission within the applicable period specified in Rule 424(b)
     under the Act; during the period specified in Section 5(d) below, not to
     file any further amendment to the Registration Statement and not to make
     any amendment or supplement to the Prospectus of which you shall not
     previously have been advised or to which you shall reasonably object after
     being so advised; and, during such period, to prepare and file with the
     Commission, promptly upon your reasonable request, any amendment to the
     Registration Statement or amendment or supplement to the Prospectus which
     may be necessary or advisable in connection with the distribution of the
     Shares by you, and to use its reasonable efforts to cause any such
     amendment to the Registration Statement to become promptly effective.

          (d)  Prior to 10:00 A.M., New York City time, on the first business
     day after the date of this Agreement and from time to time thereafter for
     such period as in the opinion of counsel for the Underwriters a prospectus
     is 
<PAGE>
 
                                      -6-

     required by law to be delivered in connection with sales by an Underwriter
     or a dealer, to furnish in New York City to each Underwriter and any dealer
     as many copies of the Prospectus (and of any amendment or supplement to the
     Prospectus) and any documents incorporated therein by reference as such
     Underwriter or dealer may reasonably request.

          (e)  If during the period specified in Section 5(d), any event shall
     occur or condition shall exist as a result of which, in the judgment of the
     Company or in the opinion of its counsel or in the opinion of counsel for
     the Underwriters, it becomes necessary to amend or supplement the
     Prospectus in order to make the statements of material facts therein not
     misleading, or if, in the judgment of the Company or in the opinion of its
     counsel or in the opinion of counsel for the Underwriters, it is necessary
     to amend or supplement the Prospectus to comply with applicable law,
     forthwith to prepare and file with the Commission an appropriate amendment
     or supplement to the Prospectus so that the statements of material facts in
     the Prospectus, as so amended or supplemented, will not in the light of the
     circumstances when it is so delivered, be misleading, or so that the
     Prospectus will comply with applicable law, and to furnish to each
     Underwriter and to any dealer as many copies thereof as such Underwriter or
     dealer may reasonably request.

          (f)  Prior to any public offering of the Shares, to cooperate with you
     and counsel for the Underwriters in connection with the registration or
     qualification of the Shares for offer and sale by the several Underwriters
     and by dealers under the state securities or Blue Sky laws of such
     jurisdictions as you may reasonably request, to continue such registration
     or qualification in effect so long as required for distribution of the
     Shares and to file such consents to service of process or other documents
     as may be necessary in order to effect such registration or qualification;
     provided, however, that the Company shall not be required in connection
     therewith to qualify as a foreign corporation in any jurisdiction in which
     it is not now so qualified or to take any action that would subject it to
     general consent to service of process or taxation other than as to matters
     and transactions relating to the Prospectus, the Registration Statement,
     any preliminary prospectus or the offering or sale of the Shares, in any
     jurisdiction in which it is not now so subject.
<PAGE>
 
                                      -7-

          (g)  To mail and make generally available to its stockholders as soon
     as reasonably practicable an earnings statement covering the twelve-month
     period ending March 31, 2000 that shall satisfy the provisions of Section
     11(a) of the Act, and to advise you in writing when such statement has been
     so made available.

          (h)  During the period of three years after the date of this
     Agreement, to furnish to you as soon as reasonably practicable after they
     become available copies of all reports or other communications furnished to
     the record holders of Common Stock or furnished to or filed with the
     Commission or any national securities exchange on which any class of
     securities of the Company is listed and such other publicly available
     information concerning the Company and its subsidiaries as you may
     reasonably request.

          (i)  Whether or not the transactions contemplated in this Agreement
     are consummated or this Agreement is terminated, to pay or cause to be paid
     all reasonable expenses incident to the performance of the Company's or the
     Selling Stockholders' obligations under this Agreement, including:  (i) the
     fees, disbursements and expenses of the Company's counsel, the Company's
     accountants and any Selling Stockholder's counsel (in addition to the
     Company's counsel) in connection with the registration and delivery of the
     Shares under the Act and all other fees and expenses in connection with the
     preparation, printing, filing and distribution of the Registration
     Statement (including financial statements and exhibits), any preliminary
     prospectus, the Prospectus and all amendments and supplements to any of the
     foregoing, including the mailing and delivering of copies thereof to the
     Underwriters and dealers in the quantities specified herein, (ii) all costs
     and expenses related to the transfer and delivery of the Shares to the
     Underwriters, including any transfer or other taxes payable thereon, (iii)
     all reasonable expenses in connection with the registration or
     qualification of the Shares for offer and sale under the securities or Blue
     Sky laws of the several states and all costs of printing or producing any
     Blue Sky Survey in connection therewith (including the filing fees and fees
     and disbursements of counsel for the Underwriters in connection with such
     registration or qualification and memoranda relating thereto), (iv) the
     filing fees and disbursements of counsel for the Underwriters in connection
     with the review and clearance of the offering of the Shares by the National
     Association of Securities Dealers, Inc., (v) all costs and 
<PAGE>
 
                                      -8-

     expenses incident to the listing of the Shares on the NYSE, (vi) the cost
     of printing certificates representing the Shares, (vii) the costs and
     charges of any transfer agent, registrar and/or depositary, and (viii) all
     other costs and expenses incident to the performance of the obligations of
     the Company and the Selling Stockholders hereunder for which provision is
     not otherwise made in this Section. The provisions of this Section shall
     not supersede or otherwise affect any agreement that the Company and the
     Selling Stockholders may otherwise have for allocation of such expenses
     among themselves. Except as expressly provided in this paragraph (i), the
     Underwriters agree to pay all of their costs and expenses, including fees
     and disbursements of their counsel.

          (j)  During the period of three years after the date of this
     Agreement, to mail and make generally available as soon as reasonably
     practicable after the end of each fiscal year to the record holders of its
     Common Stock a financial report of the Company and its subsidiaries on a
     consolidated basis (and a similar financial report of all unconsolidated
     subsidiaries, if any), all such financial reports to include a consolidated
     balance sheet, a consolidated statement of operations, a consolidated
     statement of cash flows and a consolidated statement of shareholders'
     equity as of the end of and for such fiscal year, together with comparable
     information as of the end of and for the preceding year, certified by
     independent public accountants, and to mail and make generally available as
     soon as reasonably practicable after the end of each quarterly period
     (except for the last quarterly period of each fiscal year) to such holders,
     a consolidated balance sheet, a consolidated statement of operations and a
     consolidated statement of cash flows (and similar financial reports of all
     unconsolidated subsidiaries, if any) as of the end of and for such period,
     and for the period from the beginning of such year to the close of such
     quarterly period, together with comparable information for the
     corresponding periods of the preceding year.

          (k)  To use its best efforts to do and perform all things required or
     necessary to be done and performed under this Agreement by the Company
     prior to the Closing Date and to satisfy all conditions precedent to the
     delivery of the Shares.

          (l)  If the Registration Statement at the time of the effectiveness of
     this Agreement does not cover all of the 
<PAGE>
 
                                      -9-



     Shares, to file a Rule 462(b) Registration Statement with the Commission
     registering the Shares not so covered in compliance with Rule 462(b) by
     11:00 A.M., New York City time, on the first business day following the
     date of this Agreement and to pay to the Commission the filing fee for such
     Rule 462(b) Registration Statement at the time of the filing thereof or to
     give irrevocable instructions for the payment of such fee pursuant to Rule
     111(b) under the Act.


          SECTION 6.  Representations and Warranties of the Company.  The
                      ---------------------------------------------      
Company represents and warrants to each Underwriter that:


          (a)  The Registration Statement has become effective (other than any
     Rule 462(b) Registration Statement to be filed by the Company after the
     effectiveness of this Agreement); any Rule 462(b) Registration Statement
     filed after the effectiveness of this Agreement will become effective no
     later than 11:00 A.M., New York City time, on the first business day
     following the date of this Agreement; and no stop order suspending the
     effectiveness of the Registration Statement is in effect, and no
     proceedings for such purpose are pending before or threatened by the
     Commission.

          (b)  (i) Each document, if any, filed or to be filed pursuant to the
     Exchange Act and incorporated by reference in the Prospectus complied or
     will comply when so filed in all material respects with the Exchange Act;
     (ii) the Registration Statement (other than any Rule 462(b) Registration
     Statement to be filed by the Company after the effectiveness of this
     Agreement), when it became effective, did not contain and, as amended, if
     applicable, will not contain any untrue statement of a material fact or
     omit to state a material fact required to be stated therein or necessary to
     make the statements therein not misleading, (iii) the Registration
     Statement (other than any Rule 462(b) Registration Statement to be filed by
     the Company after the effectiveness of this Agreement) and the Prospectus
     comply and, as amended or supplemented, if applicable, will comply in all
     material respects with the Act, (iv) if the Company is required to file a
     Rule 462(b) Registration Statement after the effectiveness of this
     Agreement, such Rule 462(b) Registration Statement and any amendments
     thereto, when they become effective (A) will not contain any untrue
     statement of a material fact or omit to state a material fact required to
     be stated therein or necessary to make the statements therein not
<PAGE>
 
                                      -10-


     misleading and (B) will comply in all material respects with the Act and
     (v) the Prospectus does not contain and, as amended or supplemented, if
     applicable, will not contain any untrue statement of a material fact or
     omit to state a material fact necessary to make the statements therein not
     misleading, except that the representations and warranties set forth in
     this paragraph do not apply to statements or omissions in the Registration
     Statement or the Prospectus (or any supplements or amendments to them)
     based upon information relating to any Underwriter furnished to the Company
     in writing by such Underwriter through you expressly for use therein.

          (c)  Each preliminary prospectus filed as part of the Registration
     Statement as originally filed or as part of any amendment thereto, or filed
     pursuant to Rule 424 under the Act, complied when so filed in all material
     respects with the Act, and did not contain an untrue statement of a
     material fact or omit to state a material fact required to be stated
     therein or necessary to make the statements therein, in the light of the
     circumstances under which they were made, not misleading, except that the
     representations and warranties set forth in this paragraph do not apply to
     statements or omissions in any preliminary prospectus based upon
     information relating to any Underwriter furnished to the Company in writing
     by or on behalf of such Underwriter through you expressly for use therein.

          (d)  Each of the Company and its subsidiaries has been duly
     incorporated, is validly existing as a corporation in good standing under
     the laws of its jurisdiction of incorporation and has the corporate power
     and authority to carry on its business as described in the Prospectus and
     to own, lease and operate its properties, and each is duly qualified and is
     in good standing as a foreign corporation authorized to do business in each
     jurisdiction in which the nature of its business or its ownership or
     leasing of property requires such qualification, except where the failure
     to be so qualified would not have a material adverse effect on the
     business, prospects, financial condition or results of operations of the
     Company and its subsidiaries, taken as a whole.

          (e)  There are no outstanding subscriptions, rights, warrants,
     options, calls, convertible securities, commitments of sale or liens
     granted or issued by the Company or any of its subsidiaries relating to or
     entitling any person to purchase or otherwise to acquire any shares of the
<PAGE>
 
                                      -11-


     capital stock of the Company or any of its  subsidiaries, except as
     otherwise disclosed in the Registration Statement and except for options
     which may be granted pursuant to the Company's stock option plans.

          (f)  All the outstanding shares of capital stock of the Company
     (including the Shares to be sold by the Selling Stockholders) have been
     duly authorized and validly issued and are fully paid, non-assessable and
     not subject to any preemptive or similar rights; and the Shares to be sold
     by the Selling Stockholders have been duly authorized and, when delivered
     to the Underwriters against payment therefor as provided by this Agreement,
     will be validly issued, fully paid and non-assessable, and the issuance of
     such Shares will not be subject to any preemptive or similar rights.

          (g)  Except as described in the Prospectus, all of the outstanding
     shares of capital stock of each of the Company's subsidiaries have been
     duly authorized and validly issued and are fully paid and non-assessable,
     and are owned by the Company, directly or indirectly through one or more
     subsidiaries, free and clear of any security interest, claim, lien,
     encumbrance or adverse interest of any nature.

          (h)  The authorized capital stock of the Company conforms as to legal
     matters to the description thereof contained in the Prospectus.

          (i)  Neither the Company nor any of its subsidiaries is in violation
     of its respective charter or by-laws or in default in the performance of
     any obligation, agreement, covenant or condition contained in any
     indenture, loan agreement, mortgage, lease or other agreement or instrument
     that is material to 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 their respective property is bound,
     except for any such default that would not have a material adverse effect
     on the Company and its subsidiaries taken as a whole.

          (j)  The execution, delivery and performance of this Agreement by the
     Company, the compliance by the Company with all the provisions hereof and
     the consummation of the transactions contemplated hereby will not (i)
     require any consent, approval, authorization or other order of, or
<PAGE>
 
                                      -12-

     qualification with, any court or governmental body or agency (except such
     as may be required under the securities or Blue Sky laws of the various
     states), (ii) conflict with or constitute a breach of any of the terms or
     provisions of, or a default under, the charter or by-laws of the Company or
     any of its subsidiaries or any indenture, loan agreement, mortgage, lease
     or other agreement or instrument that is material to 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 their respective property is bound, (iii) violate or conflict with any
     applicable law or any rule, regulation, judgment, order or decree of any
     court or any governmental body or agency having jurisdiction over the
     Company, any of its subsidiaries or their respective property or (iv)
     result in the suspension, termination or revocation of any Authorization
     (as defined below) of the Company or any of its subsidiaries or any other
     impairment of the rights of the holder of any such Authorization which, in
     the case of any conflict, breach, default, violation, suspension,
     termination or revocation described in clauses (ii) through (iv) of this
     paragraph (j), would result in a material adverse effect on the Company and
     its subsidiaries taken as a whole.

          (k)  There are no legal or governmental proceedings pending or
     threatened to which the Company or any of its subsidiaries is or, to the
     knowledge of the Company, could be a party or to which any of their
     respective property is or could be subject that are required to be
     described in the Registration Statement or the Prospectus and are not so
     described; nor are there any statutes, regulations, contracts or other
     documents that are required to be described in the Registration Statement
     or the Prospectus or to be filed as exhibits to the Registration Statement
     that are not so described or filed as required.

          (l)  Except as disclosed in the Prospectus, neither the Company nor
     any of its subsidiaries has violated any foreign, federal, state or local
     law or regulation relating to the protection of human health and safety,
     the environment or hazardous or toxic substances or wastes, pollutants or
     contaminants ("Environmental Laws"), any provisions of the Employee
     Retirement Income Security Act of 1974, as amended, or any provisions of
     the Foreign Corrupt Practices Act or the rules and regulations promulgated
     thereunder, except for such violations which, singly or in the aggregate,
     would not have a material adverse effect on 
<PAGE>
 
                                      -13-



     the business, prospects, financial condition or results of operation of the
     Company and its subsidiaries, taken as a whole.

          (m)  Each of the Company and its subsidiaries has such permits,
     licenses, consents, exemptions, franchises, authorizations and other
     approvals (each, an "Authorization") of, and has made all filings with and
     notices to, all governmental or regulatory authorities and self-regulatory
     organizations and all courts and other tribunals, including, without
     limitation, under any applicable Environmental Laws, as are necessary to
     own, lease, license and operate its respective properties and to conduct
     its business, except where the failure to have any such Authorization or to
     make any such filing or notice would not, singly or in the aggregate, have
     a material adverse effect on the business, prospects, financial condition
     or results of operations of the Company and its subsidiaries, taken as a
     whole.  Each such Authorization is valid and in full force and effect and
     each of the Company and its subsidiaries is in compliance with all the
     material terms and conditions thereof and with the rules and regulations of
     the authorities and governing bodies having jurisdiction with respect
     thereto; and no event has occurred (including, without limitation, the
     receipt of any notice from any authority or governing body) which allows
     or, after notice or lapse of time or both, would allow, revocation,
     suspension or termination of any such Authorization or results or, after
     notice or lapse of time or both, would result in any other impairment of
     the rights of the holder of any such Authorization except for such events
     which, singly or in the aggregate, would not have a material adverse effect
     on the business, prospects, financial condition or results of operation of
     the Company and its subsidiaries, taken as a whole; and such Authorizations
     contain no restrictions that are burdensome to the Company or any of its
     subsidiaries; except as disclosed in the Prospectus or where such failure
     to be valid and in full force and effect or to be in compliance, the
     occurrence of any such event or the presence of any such restriction would
     not, singly or in the aggregate, have a material adverse effect on the
     business, prospects, financial condition or results of operations of the
     Company and its subsidiaries, taken as a whole.

          (n)  Except as disclosed in the Prospectus, there are no costs or
     liabilities associated with Environmental Laws (including, without
     limitation, any capital or operating 
<PAGE>
 
                                      -14-



     expenditures required for clean-up, closure of properties or compliance
     with Environmental Laws or any Authorization, any related constraints on
     operating activities and any potential liabilities to third parties) which
     would, singly or in the aggregate, have a material adverse effect on the
     business, prospects, financial condition or results of operations of the
     Company and its subsidiaries, taken as a whole.

          (o)  This Agreement has been duly authorized, executed and delivered
     by the Company.

          (p)  Ernst & Young are independent public accountants with respect to
     the Company and its subsidiaries as required by the Act.

          (q)  The consolidated financial statements included in the
     Registration Statement and the Prospectus (and any amendment or supplement
     thereto), together with related schedules and notes, present fairly, in all
     material respects, the consolidated financial position of the Company and
     its subsidiaries at September 30, 1998 and 1997 and the consolidated
     results of their operations and their cash flows for each of the three
     years in the period ended September 30, 1998 in conformity with generally
     accepted accounting principles; the related financial statement schedules,
     when considered in relation to the basic financial statements taken as a
     whole, present fairly in all material respects the information set forth
     therein; the supporting schedules, if any, included in the Registration
     Statement present fairly in accordance with generally accepted accounting
     principles the information required to be stated therein; and the other
     financial and statistical information and data set forth in the
     Registration Statement and the Prospectus (and any amendment or supplement
     thereto) are, in all material respects, accurately presented and prepared
     on a basis consistent with such financial statements and the books and
     records of the Company.

          (r)  The Company is not and, after giving effect to the offering and
     sale of the Shares and the application of the proceeds thereof as described
     in the Prospectus, will not be, an "investment company" as such term is
     defined in the Investment Company Act of 1940, as amended.

          (s)  There are no contracts, agreements or understandings between the
     Company and any person granting such person the right to require the
     Company to file a regis-
<PAGE>
 
                                      -15-

     tration statement under the Act with respect to any securities of the
     Company or to require the Company to include such securities with the
     Shares registered pursuant to the Registration Statement.

          (t)  Since the respective dates as of which information is given in
     the Prospectus other than as set forth in the Prospectus (exclusive of any
     amendments or supplements thereto subsequent to the date of this
     Agreement), (i) there has not occurred  any material adverse change or any
     development involving a prospective material adverse change in the
     condition, financial or otherwise, or the earnings, business, management or
     operations of the Company and its subsidiaries, taken as a whole, (ii)
     there has not been any material adverse change or any development involving
     a prospective material adverse change in the capital stock or in the long-
     term debt of the Company or any of its subsidiaries and (iii) other then in
     the ordinary course of business, consistent with past experience, neither
     the Company nor any of its subsidiaries has incurred any material liability
     or obligation, direct or contingent.

          (u)  Each certificate signed by any officer of the Company and
     delivered to the Underwriters or counsel for the Underwriters shall be
     deemed to be a representation and warranty by the Company to the
     Underwriters as to the matters covered thereby.


          SECTION 7.  Representations and Warranties of the Selling
                      ---------------------------------------------
Stockholders.  Each Selling Stockholder represents and warrants to each
------------
Underwriter that:


          (a)  Such Selling Stockholder is the lawful owner of the Shares to be
     sold by such Selling Stockholder pursuant to this Agreement and has, and on
     the Closing Date will have, good and clear title to such Shares, free of
     all restrictions on transfer, liens, encumbrances, security interests,
     equities and claims whatsoever.

          (b)  Such Selling Stockholder has, and on the Closing Date will have,
     full legal right, power and authority, and all authorization and approval
     required by law, to enter into this Agreement and to sell, assign, transfer
     and deliver the Shares to be sold by such Selling Stockholder in the manner
     provided herein and therein.
<PAGE>
 
                                      -16-


          (c)  This Agreement has been duly authorized, executed and delivered
     by or on behalf of such Selling Stockholder.

          (d)  Upon delivery of and payment for the Shares to be sold by such
     Selling Stockholder pursuant to this Agreement, good and clear title to
     such Shares will pass to the Underwriters, free of all restrictions on
     transfer, liens, encumbrances, security interests, equities and claims
     whatsoever, except any restrictions, liens, encumbrances, security
     interests, equities and claims arising out of any act of the Underwriters.

          (e)  The execution, delivery and performance of this Agreement by the
     Selling Stockholders, the compliance by such Selling Stockholders with all
     the provisions hereof and thereof and the consummation of the transactions
     contemplated hereby and thereby will not (i) require any consent, approval,
     authorization or other order of, or qualification with,  any court or
     governmental body or agency (except such as may be required under the
     securities or Blue Sky laws of the various states), (ii) conflict with or
     constitute a breach of any of the terms or provisions of, or a default
     under, the organizational documents of such Selling Stockholder or any
     indenture, loan agreement, mortgage, lease or other agreement or instrument
     to which such Selling Stockholder is a party or by which such Selling
     Stockholder or  any property of such Selling Stockholder is bound or (iii)
     violate or conflict with any applicable law or any rule, regulation,
     judgment, order or decree of any court or any governmental body or agency
     having jurisdiction over such Selling Stockholder or any property of such
     Selling Stockholder, except such conflict, breach, default or violation
     described in clauses (ii) through (iii) of this paragraph (e), which would
     not result in a material adverse effect on such Selling Stockholder or the
     Offering.

          (f)  The information in the Registration Statement under the caption
     "Selling Stockholders" which specifically relates to such Selling
     Stockholder does not, and will not on the Closing Date, contain any untrue
     statement of a material fact or omit to state any material fact required to
     be stated therein or necessary to make the statements therein, in the light
     of the circumstances under which they were made, not misleading.
<PAGE>
 
                                      -17-


          (g)  At any time during the period described in Section 5(d), if there
     is any change in the information referred to in Section 7(f), such Selling
     Stockholder will notify you of such change as soon as it is reasonably
     practicable.

          (h)  Each certificate signed by or on behalf of such Selling
     Stockholder and delivered to the Underwriters or counsel for the
     Underwriters shall be deemed to be a representation and warranty by such
     Selling Stockholder to the Underwriters as to the matters covered thereby.


          SECTION 8.  Indemnification.  (a)  The Company agrees to indemnify and
                      ---------------                                           
hold harmless each Underwriter, its directors, its officers and each person, if
any, who controls any Underwriter within the meaning of Section 15 of the Act or
Section 20 of the Exchange Act, from and against any and all losses, claims,
damages, liabilities and judgments (including, without limitation, any legal or
other expenses incurred in connection with investigating or defending any such
matter) caused by any untrue statement or alleged untrue statement of a material
fact contained in the Registration Statement (or any amendment thereto), the
Prospectus (or any amendment or supplement thereto) or any preliminary
prospectus, or caused by any omission or alleged omission to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading, except insofar as such losses, claims, damages,
liabilities or judgments are caused by any such untrue statement or omission or
alleged untrue statement or omission based upon information relating to any
Underwriter furnished in writing to the Company by such Underwriter through you
expressly for use therein; provided, however, that the foregoing indemnity
agreement with respect to any preliminary prospectus shall not inure to the
benefit of any Underwriter who failed to deliver a Prospectus, as then amended
or supplemented (so long as the Prospectus and any amendment or supplement
thereto was provided by the Company to the several Underwriters in the requisite
quantity and on a timely basis to permit proper delivery on or prior to the
Closing Date) to the person asserting any losses, claims, damages, liabilities
or judgments caused by any untrue statement or alleged untrue statement of a
material fact contained in such preliminary prospectus, or caused by any
omission or alleged omission to state therein a material fact required to be
stated therein or necessary to make the statements therein not misleading, if
such material misstatement or omission or alleged material misstatement or
omission was cured in the Prospectus, as so amended or supplemented, and such
Prospectus was required by law to be de-
<PAGE>
 
                                      -18-


livered at or prior to the written confirmation of sale to such person, unless
such failure is the result of noncompliance by the Company with Section 5(d)
hereof.

          (b)  Each Selling Stockholder agrees, severally and not jointly, to
indemnify and hold harmless each Underwriter, its directors, its officers and
each person, if any, who controls any Underwriter within the meaning of Section
15 of the Act or Section 20 of the Exchange Act, to the same extent and subject
to the same exceptions and limitations as the foregoing indemnity from the
Company to such Underwriter, its directors, its officers and each person, if
any, who control such Underwriter, but only with reference to information
relating to such Selling Stockholder furnished in writing to the Company
expressly for use in the Registration Statement (or any amendment thereto), the
Prospectus (or any amendment or supplement thereto) or any preliminary
prospectus.  Notwithstanding the foregoing, the aggregate liability of any
Selling Stockholder pursuant to this Section 8(b) shall be limited to an amount
equal to the total proceeds (before deducting underwriting discounts and
commissions and expenses) received by such Selling Stockholder from the
Underwriters for the sale of the Shares sold by such Selling Stockholder
hereunder.

          (c)  Each Underwriter agrees, severally and not jointly, to indemnify
and hold harmless the Company, its directors, its officers who sign the
Registration Statement, each person, if any, who controls the Company within the
meaning of Section 15 of the Act or Section 20 of the Exchange Act, each Selling
Stockholder and each person, if any, who controls such Selling Stockholder
within the meaning of Section 15 of the Act or Section 20 of the Exchange Act to
the same extent as the foregoing indemnity from the Company to such Underwriter
but only with reference to information relating to such Underwriter furnished in
writing to the Company by or on behalf of such Underwriter through you expressly
for use in the Registration Statement (or any amendment thereto), the Prospectus
(or any amendment or supplement thereto) or any preliminary prospectus.

          (d)  In case any action shall be commenced involving any person in
respect of which indemnity may be sought pursuant to Section 8(a), 8(b) or 8(c)
(the "indemnified party"), the indemnified party shall promptly notify the
person against whom such indemnity may be sought (the "indemnifying party") in
writing and the indemnifying party shall assume the defense of such action,
including the employment of counsel reasonably satisfactory to the indemnified
party and the payment of all fees and expenses of such counsel, as incurred
(except that in 
<PAGE>
 
                                      -19-

the case of any action in respect of which indemnity may be sought pursuant to
both Sections 8(a), 8(b) and 8(c), the Underwriters shall not be required to
assume the defense of such action pursuant to this Section 8(d), but may employ
separate counsel and participate in the defense thereof, but the fees and
expenses of such counsel, except as provided below, shall be at the expense of
such Underwriter). Any indemnified party shall have the right to employ separate
counsel in any such action and participate in the defense thereof, but the fees
and expenses of such counsel shall be at the expense of the indemnified party
unless (i) the employment of such counsel shall have been specifically
authorized in writing by the indemnifying party, (ii) the indemnifying party
shall have failed to assume the defense of such action or employ counsel
reasonably satisfactory to the indemnified party or (iii) the named parties to
any such action (including any impleaded parties) include both the indemnified
party and the indemnifying party, and the indemnified party shall have been
advised by such counsel that there may be one or more legal defenses available
to it which are different from or additional to those available to the
indemnifying party (in which case the indemnifying party shall not have the
right to assume the defense of such action on behalf of the indemnified party).
In any such case, the indemnifying party shall not, in connection with any one
action or separate but substantially similar or related actions in the same
jurisdiction arising out of the same general allegations or circumstances, be
liable for (i) the fees and expenses of more than one separate firm of attorneys
(in addition to any local counsel) for all Underwriters, their officers and
directors and all persons, if any, who control any Underwriter within the
meaning of either Section 15 of the Act or Section 20 of the Exchange Act, (ii)
the fees and expenses of more than one separate firm of attorneys (in addition
to any local counsel) for the Company, its directors, its officers who sign the
Registration Statement and all persons, if any, who control the Company within
the meaning of either such Section and (iii) the fees and expenses of more than
one separate firm of attorneys (in addition to any local counsel) for all
Selling Stockholders and all persons, if any, who control any Selling
Stockholder within the meaning of either such Section, and all such fees and
expenses shall be reimbursed as they are incurred. In the case of any such
separate firm for the Underwriters, their officers and directors and such
control persons of any Underwriters, such firm shall be designated in writing by
Donaldson, Lufkin & Jenrette Securities Corporation. In the case of any such
separate firm for the Company and such directors, officers and control persons
of the Company, such firm shall be designated in writing by the Company. In the
case of
<PAGE>
 
                                      -20-

any such separate firm for the Selling Stockholders and such control persons of
any Selling Stockholders, such firm shall be designated in writing by 399
Venture Partners, Inc. The indemnifying party shall indemnify and hold harmless
the indemnified party from and against any and all losses, claims, damages,
liabilities and judgments by reason of any settlement of any action effected
with its written consent. No indemnifying party shall, without the prior written
consent of the indemnified party, effect any settlement or compromise of, or
consent to the entry of judgment with respect to, any pending or threatened
action in respect of which the indemnified party is or could have been a party
and indemnity or contribution may be or could have been sought hereunder by the
indemnified party, unless such settlement, compromise or judgment (i) includes
an unconditional release of the indemnified party from all liability on claims
that are or could have been the subject matter of such action and (ii) does not
include a statement as to or an admission of fault, culpability or a failure to
act, by or on behalf of the indemnified party.

          (e)  To the extent the indemnification provided for in this Section 8
is unavailable to an indemnified party or insufficient in respect of any losses,
claims, damages, liabilities or judgments referred to therein, then each
indemnifying party, in lieu of indemnifying such indemnified party, shall
contribute to the amount paid or payable by such indemnified party as a result
of such losses, claims, damages, liabilities and judgments (i) in such
proportion as is appropriate to reflect the relative benefits received by the
Company and the Selling Stockholders on the one hand and the Underwriters on the
other hand from the offering of the Shares or (ii) if the allocation provided by
clause 8(e)(i) above is not permitted by applicable law, in such proportion as
is appropriate to reflect not only the relative benefits referred to in clause
8(e)(i) above but also the relative fault of the Company and the Selling
Stockholders on the one hand and the Underwriters on the other hand in
connection with the statements or omissions which resulted in such losses,
claims, damages, liabilities or judgments, as well as any other relevant
equitable considerations.  The relative benefits received by the Company and the
Selling Stockholders on the one hand and the Underwriters on the other hand
shall be deemed to be in the same proportion as the total net proceeds from the
offering (after deducting underwriting discounts and commissions, but before
deducting expenses) received by the Selling Stockholders, and the total
underwriting discounts and commissions received by the Underwriters, bear to the
total price to the public of the Shares, in each case as set forth in the table
on the cover page of the Prospectus.  
<PAGE>
 
                                      -21-

The relative fault of the Company and the Selling Stockholders on the one hand
and the Underwriters on the other hand shall be determined by reference to,
among other things, whether the untrue or alleged untrue statement of a material
fact or the omission or alleged omission to state a material fact relates to
information supplied by the Company or the Selling Stockholders on the one hand
or the Underwriters on the other hand and the parties' relative intent,
knowledge, access to information and opportunity to correct or prevent such
statement or omission.

          The Company, the Selling Stockholders and the Underwriters agree that
it would not be just and equitable if contribution pursuant to this Section 8(e)
were determined by pro rata allocation (even if the Underwriters were treated as
one entity for such purpose) or by any other method of allocation which does not
take account of the equitable considerations referred to in the immediately
preceding paragraph.  The amount paid or payable by an indemnified party as a
result of the losses, claims, damages, liabilities or judgments referred to in
the immediately preceding paragraph shall be deemed to include, subject to the
limitations set forth above, any legal or other expenses incurred by such
indemnified party in connection with investigating or defending any matter,
including any action, that could have given rise to such losses, claims,
damages, liabilities or judgments.  Notwithstanding the provisions of this
Section 8, no Underwriter shall be required to contribute any amount in excess
of the amount by which the total price at which the Shares underwritten by it
and distributed to the public were offered to the public exceeds the amount of
any damages which such Underwriter has otherwise been required to pay by reason
of such untrue or alleged untrue statement or omission or alleged omission.  No
person guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Act) shall be entitled to contribution from any person who was not
guilty of such fraudulent misrepresentation.  The Selling Stockholders' and the
Underwriters' obligations to contribute pursuant to this Section 8(e) are
several in proportion to the respective number of Shares purchased or sold by
each of the Selling Stockholders or Underwriters hereunder, and not joint.

          (f)  The remedies provided for in this Section 8 are not exclusive and
shall not limit any rights or remedies which may otherwise be available to any
indemnified party at law or in equity.

          (g)  Each Selling Stockholder hereby accepts the jurisdiction of any
state or federal court in the state of New 
<PAGE>
 
                                      -22-

York in such action, and waives, to the fullest extent permitted by applicable
law, any defense based upon lack of personal jurisdiction or venue. A copy of
any such process shall be sent or given to such Selling Stockholder, at the
address for notices specified in Section 12 hereof.

          SECTION 9.  Conditions of Underwriters' Obligations.  The several
                      ---------------------------------------              
obligations of the Underwriters to purchase the Shares under this Agreement are
subject to the satisfaction of each of the following conditions:


          (a)  All the representations and warranties of the Company contained
     in this Agreement shall be true and correct on the Closing Date with the
     same force and effect as if made on and as of the Closing Date.

          (b)  If the Company is required to file a Rule 462(b) Registration
     Statement after the effectiveness of this Agreement, such Rule 462(b)
     Registration Statement shall have become effective by 10:00 P.M., New York
     City time, on the date of this Agreement; and no stop order suspending the
     effectiveness of the Registration Statement shall have been issued and no
     proceedings for that purpose shall have been commenced or shall be pending
     before or contemplated by the Commission.

          (c)  You shall have received on the Closing Date a certificate dated
     the Closing Date, signed by Kurt J. Hilzinger and Michael D. DiCandilo, in
     their capacities as the Senior Vice President, Chief Operating Officer and
     Chief Financial Officer and Vice President and Controller of the Company,
     confirming the matters set forth in Sections 6(t), 9(a) and 9(b) and that
     the Company has complied in all material respects with all of the
     agreements and satisfied all of the conditions herein contained and
     required to be complied with or satisfied by the Company on or prior to the
     Closing Date.

          (d)  Since the respective dates as of which information is given in
     the Prospectus other than as set forth in the Prospectus (exclusive of any
     amendments or supplements thereto subsequent to the date of this
     Agreement), (i) there shall not have occurred  any change or any
     development involving a prospective change in the condition, financial or
     otherwise, or the earnings, business, management or operations of the
     Company and its subsidiaries, taken as a whole, (ii) there shall not have
     been any change or any development involving a prospective change 
<PAGE>
 
                                      -23-

     in the capital stock or in the long-term debt of the Company or any of its
     subsidiaries and (iii) neither the Company nor any of its subsidiaries
     shall have incurred any liability or obligation, direct or contingent, the
     effect of which, in any such case described in clause 9(d)(i), 9(d)(ii) or
     9(d)(iii), in your judgment, is material and adverse to the Company and its
     subsidiaries taken as a whole and, in your judgment, makes it impracticable
     to market the Shares on the terms and in the manner contemplated in the
     Prospectus.

          (e)  All the representations and warranties of each Selling
     Stockholder contained in this Agreement shall be true and correct on the
     Closing Date with the same force and effect as if made on and as of the
     Closing Date and you shall have received on the Closing Date a certificate
     dated the Closing Date from each Selling Stockholder to such effect and to
     the effect that such Selling Stockholder has complied in all material
     respects with all of the agreements and satisfied all of the conditions
     herein contained and required to be complied with or satisfied by such
     Selling Stockholder on or prior to the Closing Date.

          (f)  Cahill Gordon & Reindel, counsel for the Underwriters, shall have
     furnished to you their written opinion, dated the Closing Date, with
     respect to the matters covered in paragraphs (i), the last clause of (ii)
     relating to the description of the Shares, (iii) and the first clause of
     (vi) relating to compliance as to form of subsection (g) below as well as
     such other related matters as you may reasonably request, and such counsel
     shall have received such papers and information as they may reasonably
     request to enable them to pass upon such matters;

          (g)  Dechert Price & Rhoads, counsel for the Company, shall have
     furnished to you their written opinion, dated the Closing Date, in form and
     substance satisfactory to you, to the effect that:

                  (i)  The Company has been duly incorporated and is validly
          existing as a corporation in good standing under the laws of Delaware,
          with corporate power and corporate authority to own its properties and
          conduct its business as described in the Prospectus;

                  (ii) The Company has an authorized capital stock as
          incorporated by reference in the Prospectus, and all of the issued
          shares of capital stock of the Com-
<PAGE>
 
                                      -24-

          pany (including the Shares being delivered on the Closing Date by the
          Selling Stockholders) have been duly and validly authorized and issued
          and are fully paid and non-assessable; and the Shares conform in all
          material respects to the description of the Common Stock incorporated
          by reference in the Prospectus;

                  (iii)  This Agreement has been duly authorized, executed and
          delivered by the Company;

                  (iv)   The Company is not an "investment company" or an entity
          "controlled by an "investment company", as such terms are defined in
          the Investment Company Act;

                  (v)    The documents incorporated by reference in the
          Prospectus and any further amendment or supplement thereto made by the
          Company prior to the Closing Date (other than any exhibits to such
          documents, the financial statements including the notes thereto and
          related schedules and other financial data contained or incorporated
          by reference therein, as to which such counsel need express no
          opinion), when they became effective or were filed with the
          Commission, as the case may be, complied as to form in all material
          respects with the requirements of the Exchange Act, as applicable, and
          the rules and regulations of the Commission thereunder; and a
          statement to the effect that although they are not passing upon and do
          not assume any responsibility for the accuracy, completeness or
          fairness of the statements contained in such documents and have not
          made any independent check or verification thereof, on the basis of
          the foregoing (relying as to materiality, to the extent they deem
          appropriate, upon the statements of officers and other representatives
          of the Company), no facts have come to their attention that have
          caused them to believe that any of such documents (other than any
          exhibits to such documents, the financial statements including the
          notes thereto and related schedules and other financial data contained
          or incorporated by reference therein, as to which such counsel need
          express no opinion), when such documents became effective or were so
          filed, as the case may be, contained, in the case of a registration
          statement which became effective under the Act, an untrue statement of
          a material fact or omitted to state a material fact re-
<PAGE>
 
                                      -25-

          quired to be stated therein or necessary to make the statements
          therein not misleading, or contained, in the case of other documents
          which were filed under the Exchange Act with the Commission, an untrue
          statement of a material fact or omitted to state a material fact
          necessary in order to make the statements therein, in the light of the
          circumstances under which they were made when such documents were so
          filed, not misleading; and

                  (vi)   The Registration Statement and the Prospectus and any
          further amendments and supplements thereto made by the Company prior
          to the Closing Date (other than any exhibits to such documents, any
          documents referred to in the first clause of (v) above and the
          financial statements including the notes thereto and related schedules
          and the other financial data contained or incorporated by reference
          therein, as to which such counsel need express no opinion) comply as
          to form in all material respects with the requirements of the Act and
          the rules and regulations thereunder; a statement to the effect that,
          although they are not passing upon and do not assume any
          responsibility for the accuracy, completeness or fairness of the
          statements contained in the Registration Statement or the Prospectus
          (except as set forth in the last clause of (ii) above), and have not
          made any independent check or verification thereof, on the basis of
          the foregoing (relying as to materiality, to the extent they deem
          appropriate, upon the statements of officers and other representatives
          of the Company), no facts have come to their attention that have
          caused them to believe that, as of its effective date, the
          Registration Statement or any further amendment thereto made by the
          Company prior to the Closing Date (other than the financial statements
          including the notes thereto and related schedules and the other
          financial data contained or incorporated by reference therein, as to
          which such counsel need express no opinion) contained an untrue
          statement of a material fact or omitted to state a material fact
          required to be stated therein or necessary to make the statements
          therein not misleading or that, as of its date, the Prospectus and any
          further amendment or supplement thereto made by the Company prior to
          the Closing Date (other than the financial statements including the
          notes thereto and related schedules and other financial data contained
          or incorporated by 
<PAGE>
 
                                      -26-

          reference therein, as to which such counsel need express no opinion)
          contained an untrue statement of a material fact or omitted to state a
          material fact necessary to make the statements therein, in the light
          of the circumstances under which they were made, not misleading or
          that, as of the Closing Date, either the Registration Statement or the
          Prospectus or any further amendment or supplement thereto made by the
          Company prior to the Closing Date (other than the financial statements
          including the notes thereto and related schedules and the other
          financial data contained or incorporated by reference therein, as to
          which such counsel need express no opinion) contains an untrue
          statement of a material fact or omits to state a material fact
          necessary to make the statements therein, in the light of the
          circumstances under which they were made, not misleading.

          In rendering such opinion, such counsel may state that their opinion
     is limited to the laws of the United States of America, the State of New
     York and the General Corporation Law of the State of Delaware, and that
     such counsel expresses no opinion with respect to the effect of any laws or
     regulations relating to the Drug Enforcement Agency, the Food and Drug
     Administration, state boards of pharmacy and departments of health, the
     Pharmaceutical Drug Marketing Act, the Department of Transportation or
     government procurement laws and regulations.  In rendering its statements
     included in (vi) above, such counsel may state that they have participated
     in conferences with officers and other representatives of the Company,
     representatives of the independent public accountants of the Company and
     representatives of the Underwriters, at which the contents of the
     Registration Statement and the Prospectus and related matters were
     discussed.

          (h)  William D. Sprague, Esq., Vice President, General Counsel and
     Secretary for the Company, shall have furnished to you his written opinion,
     dated the Closing Date in form and substance satisfactory to you, to the
     effect that:

                  (i) The Company has been duly qualified as a foreign
          corporation for the transaction of business and is in good standing
          under the laws of each other jurisdiction in which it owns or leases
          properties or conducts any business so as to require such
          qualification, or is subject to no material liability or 
<PAGE>
 
                                      -27-



          disability by reason of failure to be so qualified in any such
          jurisdiction (such counsel being entitled to rely in respect of the
          opinion in this clause upon opinions of local counsel and in respect
          of matters of fact upon certificates of officers of the Company,
          provided that such counsel shall state that they believe that both you
          and they are justified in relying upon such opinions and
          certificates);

                  (ii)   Each subsidiary of the Company has been duly
          incorporated and is validly existing as a corporation in good standing
          under the laws of its jurisdiction of incorporation; and all of the
          issued shares of capital stock of each such subsidiary have been duly
          and validly authorized and issued, are fully paid and non-assessable,
          and (except as set forth in the Prospectus) are owned directly or
          indirectly by the Company, free and clear of all liens, encumbrances,
          equities or claims (such counsel being entitled to rely in respect of
          the opinion in this clause upon opinions of local counsel and in
          respect of matters of fact upon certificates of officers of the
          Company or its subsidiaries, provided that such counsel shall state
          that they believe that both you and they are justified in relying upon
          such opinions and certificates);

                  (iii)  To the best of such counsel's knowledge and other than
          as set forth in the Prospectus, there are no legal or governmental
          proceedings pending to which the Company or any of its subsidiaries is
          a party or of which any property of the Company or any of its
          subsidiaries is the subject which could reasonably be expected to be
          determined adversely to the Company or any of its subsidiaries and
          would individually or in the aggregate have a material adverse effect
          on the current or future consolidated financial position,
          stockholders' equity or results of operations of the Company and its
          subsidiaries taken as a whole; and, to the best of such counsel's
          knowledge, no such proceedings are threatened or contemplated by
          governmental authorities or threatened by others;

                  (iv)   The sale of the Shares being delivered at the Closing
          Date and the compliance by the Company with all of the provisions of
          this Agreement and the consummation of the transactions herein
          contemplated will not conflict with or result in a breach or vio
<PAGE>
 
                                      -28-

          lation of any of the terms or provisions of, or constitute a default
          under, any indenture, mortgage, deed of trust, loan agreement or other
          agreement or instrument known to such counsel to which the Company or
          any of its subsidiaries is a party or by which the Company or any of
          its subsidiaries is bound or to which any of the property or assets of
          the Company or any of its subsidiaries is subject, nor will such
          action result in any violation of the provisions of the Certificate of
          Incorporation or By-laws of the Company or any statute or any order,
          rule or regulation known to such counsel of any court or governmental
          agency or body having jurisdiction over the Company or any of its
          subsidiaries or any of their properties except, in each case (other
          than with respect to such Certificate of Incorporation or By-laws),
          for such conflicts, violations, breaches or defaults which would not
          result in a material adverse change in the business, prospects,
          financial conditions or results of operations of the Company and its
          subsidiaries taken as a whole;

                  (v)    No consent, approval, authorization, order,
          registration or qualification of or with any such court or
          governmental agency or body is required for the sale of the Shares or
          the consummation by the Company of the transactions contemplated by
          this Agreement, except the registration under the Act of the Shares,
          and such consents, approvals, authorizations, registrations or
          qualifications as may be required under state or foreign securities or
          Blue Sky laws in connection with the purchase and distribution of the
          Shares by the Underwriters or under the rules of the National
          Association of Securities Dealers, Inc.;

                  (vi)   Neither the Company nor any of its subsidiaries is in
          violation of its Certificate of Incorporation or By-laws or in default
          in the performance or observance of any material obligation,
          agreement, covenant or condition contained in any indenture, mortgage,
          deed of trust, loan agreement, lease or other agreement or instrument
          to which it is a party or by which it or any of its properties may be
          bound which breach or default (other than with respect to such
          Certificate of Incorporation or By-laws) would have a material adverse
          effect on the Company and its subsidiaries taken as a whole;
<PAGE>
 
                                      -29-

                  (vii)   The documents incorporated by reference in the
          Prospectus or any further amendment or supplement thereto made by the
          Company prior to the Closing Date (other than any exhibits to such
          documents, the financial statements including the notes thereto and
          related schedules and other financial data contained or incorporated
          by reference therein, as to which such counsel need express no
          opinion), when they became effective or were filed with the
          Commission, as the case may be, complied as to form in all material
          respects with the requirements of the Act or the Exchange Act, as
          applicable, and the rules and regulations of the Commission
          thereunder; although he does not assume any responsibility for the
          accuracy, completeness or fairness of the statements contained in such
          documents, no facts have come to his attention that have caused him to
          believe that any of such documents, when such documents became
          effective or were so filed, as the case may be, contained, in the case
          of a registration statement which became effective under the Act, an
          untrue statement of a material fact or omitted to state a material
          fact required to be stated therein or necessary to make the statements
          therein not misleading, or, in the case of other documents which were
          filed under the Exchange Act with the Commission, an untrue statement
          of a material fact or omitted to state a material fact necessary in
          order to make the statements therein, in the light of the
          circumstances under which they were made when such documents were so
          filed, not misleading; and

                  (viii)  The Registration Statement and the Prospectus and any
          further amendments and supplements thereto made by the Company prior
          to the Closing Date (other than any exhibits to such documents, any
          documents incorporated by reference in the Prospectus or any further
          amendment or supplement thereto made by the Company prior to the
          Closing Date and the financial statements including the notes thereto
          and related schedules and the other financial data contained or
          incorporated by reference therein, as to which such counsel need
          express no opinion) comply as to form in all material respects with
          the requirements of the Act and the rules and regulations thereunder;
          although he does not assume any responsibility for the accuracy,
          completeness or fairness of the statements contained in the
          Registration Statement or 
<PAGE>
 
                                      -30-

          the Prospectus, no facts have come to his attention that have caused
          him to believe that, as of its effective date, the Registration
          Statement or any further amendment thereto made by the Company prior
          to the Closing Date (other than the financial statements including the
          notes thereto and related schedules and the other financial data
          contained or incorporated by reference therein, as to which such
          counsel need express no opinion) contained an untrue statement of a
          material fact or omitted to state a material fact required to be
          stated therein or necessary to make the statements therein not
          misleading or that, as of its date, the Prospectus or any further
          amendment or supplement thereto made by the Company prior to the
          Closing Date (other than the financial statements including the notes
          thereto and related schedules and the other financial data contained
          or incorporated by reference therein, as to which such counsel need
          express no opinion) contained an untrue statement of a material fact
          or omitted to state a material fact necessary to make the statements
          therein, in the light of the circumstances under which they were made,
          not misleading or that, as of the Closing Date, either the
          Registration Statement or the Prospectus or any further amendment or
          supplement thereto made by the Company prior to the Closing Date
          (other than the financial statements including the notes thereto and
          related schedules and the other financial data contained or
          incorporated by reference therein, as to which such counsel need
          express no opinion) contains an untrue statement of a material fact or
          omits to state a material fact necessary to make the statements
          therein, in the light of the circumstances under which they were made,
          not misleading; and, to the best of his knowledge, there is not any
          amendment to the Registration Statement required to be filed or any
          contracts or other documents of a character required to be filed as an
          exhibit to the Registration Statement or required to be incorporated
          by reference into the Prospectus or required to be described in the
          Registration Statement or the Prospectus which are not filed or
          incorporated by reference or described as required.


          (i)  Counsel for each of the Selling Stockholders, Karen Kirchen for
     399 Venture Partners, Inc. and Stephen E. Dietz for Citigroup Foundation,
     each shall have furnished to you her or his written opinion with respect 
<PAGE>
 
                                      -31-


     to each of the Selling Stockholders for whom she or he is acting as
     counsel, dated the Closing Date, in form and substance satisfactory to you,
     to the effect that:

                  (i)   This Agreement has been duly executed and delivered by
          or on behalf of such Selling Stockholder; and the sale of the Shares
          to be sold by such Selling Stockholder hereunder and thereunder and
          the compliance by such Selling Stockholder with all of the provisions
          of this Agreement and the consummation of the transactions herein
          contemplated will not conflict with or result in a breach or violation
          of any terms or provisions of, or constitute a default under, any
          indenture, mortgage, deed of trust, loan agreement or other agreement
          or instrument known to such counsel after due inquiry to which such
          Selling Stockholder is a party or by which such Selling Stockholder is
          bound, or to which any of the property or assets of such Selling
          Stockholder is subject, nor will such action result in any violation
          of the provisions of the Certificate of Incorporation or By-laws of
          such Selling Stockholder if such Selling Stockholder is a corporation
          or any statute, order, rule or regulation known to such counsel of any
          court or governmental agency or body having jurisdiction over such
          Selling Stockholder or the property of such Selling Stockholder (where
          the consequences of such conflict, breach, violation or default would
          affect the ability of such Selling Stockholder to sell its Shares to
          the Underwriters pursuant to this Agreement or materially affect the
          ability of such Selling Stockholder to perform its obligations under
          this Agreement);

                  (ii)  No consent, approval, authorization or order of any
          court or the State of Delaware (as it relates to the Delaware General
          Corporate Law, the State of New York or any federal governmental body
          or agency) is required for the consummation of the transactions
          contemplated by this Agreement in connection with the Shares to be
          sold by such Selling Stockholder hereunder, except such consents,
          approvals, authorization or orders which have been duly obtained and
          are in full force and effect, such as have been obtained under the Act
          and such as may be required by the National Association of Securities
          Dealers, Inc., under state securities or Blue Sky 
<PAGE>
 
                                      -32-

          laws in connection with the purchase and distribution of such Shares
          by the Underwriters;

                  (iii)   Good and valid title to such Shares, free and clear of
          all liens, encumbrances, equities or claims, in each case created by
          the Selling Stockholders, has been transferred to each of the several
          Underwriters who have purchased such Shares in good faith and without
          notice of any such lien, encumbrance, equity or claim or any other
          adverse claim within the meaning of the Uniform Commercial Code.


          In rendering such opinion, such counsel may state that they express no
     opinion as to the laws of any jurisdiction outside the United States and in
     rendering the opinion in subparagraph (iii) such counsel may rely upon a
     certificate of such Selling Stockholder in respect of matters of fact as to
     ownership of, and liens, encumbrances, equities or claims on the Shares
     sold by such Selling Stockholder, provided that such counsel shall state
     that they believe that both you and they are justified in relying upon such
     certificate.

          The opinions described above shall be rendered to you at the request
     of the Company and the Selling Stockholders and shall so state therein.

          In giving such opinions, Dechert Price & Rhoads and William D. Sprague
     may state that their opinion and belief are based upon their participation
     in the preparation of the Registration Statement and Prospectus and any
     amendments or supplements thereto and documents incorporated therein by
     reference and review and discussion of the contents thereof, but is without
     independent check or verification except as specified.  In giving such
     opinions, Cahill Gordon & Reindel may state that their opinion and belief
     are based upon their participation in the preparation of the Registration
     Statement and Prospectus and any amendments or supplements thereto (other
     than the documents incorporated therein by reference) and review and
     discussion of the contents thereof (including the documents incorporated
     therein by reference), but are without independent check or verification
     except as specified.

          (j)  You shall have received, on each of the date hereof and the
     Closing Date, a letter dated the date hereof or the Closing Date, as the
     case may be, in form and substance satisfactory to you, from Ernst & Young,
     in-
<PAGE>
 
                                      -33-

     dependent public accountants, containing the information and statements of
     the type ordinarily included in accountants' "comfort letters" to
     Underwriters with respect to the financial statements and certain financial
     information contained in or incorporated by reference into the Registration
     Statement and the Prospectus.

          (k)  The Company shall have delivered to you the agreements specified
     in Section 2 hereof which agreements shall be in full force and effect on
     the Closing Date.

          (l)  The Company and the Selling Stockholders shall not have failed on
     or prior to the Closing Date to perform or comply in any material respect
     with any of the agreements herein contained and required to be performed or
     complied with by the Company or the Selling Stockholders, as the case may
     be, on or prior to the Closing Date.


          SECTION 10.  Effectiveness of Agreement and Termination.  This
                       ------------------------------------------       
Agreement shall become effective upon the execution and delivery of this
Agreement by the parties hereto.


          This Agreement may be terminated at any time on or prior to the
Closing Date by you by written notice to the Company and the Selling
Stockholders if any of the following has occurred:  (i) any outbreak or
escalation of hostilities or other national or international calamity or crisis
or change in economic conditions or in the financial markets of the United
States or elsewhere that, in your judgment, is material and adverse and, in your
judgment, makes it impracticable to market the Shares on the terms and in the
manner contemplated in the Prospectus, (ii) the suspension or material
limitation of trading in securities or other instruments on the New York Stock
Exchange, the American Stock Exchange, the Chicago Board of Options Exchange,
the Chicago Mercantile Exchange, the Chicago Board of Trade or the Nasdaq
National Market or limitation on prices for securities or other instruments on
any such exchange or the Nasdaq National Market, (iii) the suspension of trading
of any securities of the Company on any exchange or in the over-the-counter
market, (iv) the enactment, publication, decree or other promulgation of any
federal or state statute, regulation, rule or order of any court or other
governmental authority which in your opinion materially and adversely affects,
or will materially and adversely affect, the business, prospects, financial
condition or results of operations of the Company and its subsidiaries, taken as
a whole, (v) the declaration of a banking moratorium by either federal or New
York State authorities or (vi) the taking of any action by any fed-
<PAGE>
 
                                      -34-

eral, state or local government or agency in respect of its monetary or fiscal
affairs which in your opinion has a material adverse effect on the financial
markets in the United States.

          If on the Closing Date any one or more of the Underwriters shall fail
or refuse to purchase the Shares which it has or they have agreed to purchase
hereunder on such date and the aggregate number of Shares which such defaulting
Underwriter or Underwriters agreed but failed or refused to purchase is not more
than one-tenth of the total number of Shares to be purchased on such date by all
Underwriters, each non-defaulting Underwriter shall be obligated severally, in
the proportion which the number of Shares set forth opposite its name in
Schedule I bears to the total number of Shares which all the non-defaulting
Underwriters have agreed to purchase, or in such other proportion as you may
specify, to purchase the Shares which such defaulting Underwriter or
Underwriters agreed but failed or refused to purchase on such date; provided
that in no event shall the number of Shares which any Underwriter has agreed to
purchase pursuant to Section 2 hereof be increased pursuant to this Section 10
by an amount in excess of one-ninth of such number of Shares without the written
consent of such Underwriter.  If on the Closing Date any Underwriter or
Underwriters shall fail or refuse to purchase Shares and the aggregate number of
Shares with respect to which such default occurs is more than one-tenth of the
aggregate number of Shares to be purchased by all Underwriters and arrangements
satisfactory to you, the Company and the Selling Stockholders for purchase of
such Shares are not made within 48 hours after such default, this Agreement will
terminate without liability on the part of any non-defaulting Underwriter, the
Company or the Selling Stockholders.  In any such case which does not result in
termination of this Agreement, either you, the Company or the Selling
Stockholders shall have the right to postpone the Closing Date, but in no event
for longer than seven days, in order that the required changes, if any, in the
Registration Statement and the Prospectus or any other documents or arrangements
may be effected.  Any action taken under this paragraph shall not relieve any
defaulting Underwriter from liability in respect of any default of any such
Underwriter under this Agreement.

          SECTION 11.  Agreements of the Selling Stockholders.  Each Selling
                       --------------------------------------               
Stockholder agrees with you and the Company:

          (a)  To pay or to cause to be paid all transfer taxes payable in
     connection with the transfer of the Shares to be sold by such Selling
     Stockholder to the Underwriters.
<PAGE>
 
                                     -35-


          (b)  To do and perform all things to be done and performed by such
     Selling Stockholder under this Agreement prior to the Closing Date and to
     satisfy all conditions precedent to the delivery of the Shares to be sold
     by such Selling Stockholder pursuant to this Agreement.


          SECTION 12.  Miscellaneous.  Notices given pursuant to any provision
                       -------------                                          
of this Agreement shall be addressed as follows:  (i) if to the Company, to
AmeriSource Health Corporation, 300 Chester Field Parkway, Malvern, Pennsylvania
19355, Attention:  General Counsel, (ii) if to 399 Venture Partners, Inc. to 399
Park Avenue, 14th Floor, Zone 4, New York, NY  10043, Attention:  Helene Shavin,
(iii) if to Citigroup Foundation to 425 Park Avenue, 2nd Floor, New York, NY
10043, Attention:  Stephen E. Dietz and (iii) if to any Underwriter or to you,
to you c/o Donaldson, Lufkin & Jenrette Securities Corporation, 277 Park Avenue,
New York, New York 10172, Attention:  Syndicate Department, or in any case to
such other address as the person to be notified may have requested in writing.

          The respective indemnities, contribution agreements, representations,
warranties and other statements of the Company, the Selling Stockholders and the
several Underwriters set forth in or made pursuant to this Agreement shall
remain operative and in full force and effect, and will survive delivery of and
payment for the Shares, regardless of (i) any investigation, or statement as to
the results thereof, made by or on behalf of any Underwriter, the officers or
directors of any Underwriter, any person controlling any Underwriter, the
Company, the officers or directors of the Company, any person controlling the
Company, any Selling Stockholder or any person controlling such Selling
Stockholder, (ii) acceptance of the Shares and payment for them hereunder and
(iii) termination of this Agreement.

          If for any reason the Shares are not delivered by or on behalf of any
Seller as provided herein (other than as a result of any termination of this
Agreement pursuant to Section 10), the Selling Stockholders agree, severally but
not jointly, to reimburse the several Underwriters for all out-of-pocket
expenses (including the fees and disbursements of counsel) incurred by them.
Notwithstanding any termination of this Agreement, the Company shall be liable
for all expenses which it has agreed to pay pursuant to Section 5(i) hereof.
The Sellers also agree, jointly and severally, to reimburse the several
Underwriters, their directors and officers and any persons controlling any of
the Underwriters for any and all fees and expenses (including, without
limitation, the fees disburse-
<PAGE>
 
                                   -36-    


ments of counsel) incurred by them in connection with enforcing their rights
hereunder (including, without limitation, pursuant to Section 8 hereof).

          Except as otherwise provided, this Agreement has been and is made
solely for the benefit of and shall be binding upon the Company, the Selling
Stockholders, the Underwriters, the Underwriters' directors and officers, any
controlling persons referred to herein, the Company's directors and the
Company's officers who sign the Registration Statement and their respective
successors and assigns, all as and to the extent provided in this Agreement, and
no other person shall acquire or have any right under or by virtue of this
Agreement.  The term "successors and assigns" shall not include a purchaser of
any of the Shares from any of the several Underwriters merely because of such
purchase.

          This Agreement shall be governed and construed in accordance with the
laws of the State of New York without regard to principles of conflicts of law
hereof.

          This Agreement may be signed in various counterparts which together
shall constitute one and the same instrument.
<PAGE>
 
                                      S-1

          Please confirm that the foregoing correctly sets forth the agreement
among the Company, the Selling Stockholders and the several Underwriters.


                              Very truly yours,


                              AMERISOURCE HEALTH CORPORATION


                              By: /s/ William D. Sprague
                                  --------------------------------
                                  Title: Vice President

    
                              399 VENTURE PARTNERS, INC.


                              By: /s/ Helene Shavin
                                  --------------------------------
                                  Title: Vice President


                              CITIGROUP FOUNDATION


                              By: /s/ Alan Okada
                                  --------------------------------
                                  Title: Treasurer
<PAGE>
 
                                      S-2


DONALDSON, LUFKIN & JENRETTE
  SECURITIES CORPORATION
SALOMON SMITH BARNEY INC.
J.P. MORGAN SECURITIES INC.
FIRST UNION CAPITAL MARKETS CORP.
MCDONALD INVESTMENTS INC.
PIPER JAFFRAY INC.

Acting severally on behalf of
  themselves and the several
  Underwriters named in
  Schedule I hereto

By  DONALDSON, LUFKIN & JENRETTE
      SECURITIES CORPORATION


By:  /s/ Michael Bruder
     ------------------------------------
     Vice President
<PAGE>
 
                                   SCHEDULE I
                                   ----------


                                                           Number of Shares
Underwriters                                               to be Purchased
------------                                               ----------------

Donaldson, Lufkin & Jenrette                                     2,940,000
  Securities Corporation              
Salomon Smith Barney, Inc.                                       1,080,000
J.P. Morgan Securities Inc.                                      1,080,000
First Union Capital Markets 
  Corp.                                                            300,000
McDonald Investments Inc.                                          300,000
Piper Jaffray Inc.                                                 300,000

                                                           ----------------

                  Total                                          6,000,000
<PAGE>
 
                                   SCHEDULE II
                                   -----------

                              Selling Stockholders
                              --------------------




                                                           Number of Shares
                                                           Being Sold
                                                           ----------------

399 Venture Partners, Inc.                                     5,480,000
Citigroup Foundation                                             520,000

                                                           ----------------

                  Total                                        6,000,000