EXHIBIT 10.1

                         REGISTRATION RIGHTS AGREEMENT



                           Dated as of June 22, 1998



                                                                    EXHIBIT 10.1

          REGISTRATION RIGHTS AGREEMENT, dated as of June 22, 1998, by McKesson
Corporation, a Delaware corporation (the "Company"), and the other undersigned
parties hereto.

          1.  Introduction; Term of Agreement The Company is a party to the
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separate Agreement and Plan of Merger (the "Merger Agreement"), dated as of June
22, 1998, among the Company, HMS Acquisition Corp., a Delaware corporation and
Hawk Medical Supply, Inc., a Delaware corporation ("Hawk"), pursuant to which
the Company has agreed, among other things, to acquire through merger Hawk and,
in connection therewith, to issue to the stockholders and warrant holders of
Hawk (the "Stockholders") shares of common stock of the Company (the "Common
Stock") as specified in the Merger Agreement. This Agreement shall become
effective upon the Effective Time (as defined in the Merger Agreement). This
Agreement shall terminate and be of no further force and effect on the second
anniversary date of the Effective Time. Certain capitalized terms used in this
Agreement are defined in section 3 hereof; references to sections shall be to
sections of this Agreement.

          2.  Registration under Securities Act, etc.
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               2.1  Registration on Request.
                    ----------------------- 

               (a)  Demand Request. Upon the written request of an Initiating
                    --------------
Holder (on its own and/or on behalf of the other Stockholders), requesting that
the Company effect the registration under the Securities Act of all or part of
such Initiating Holder's Registrable Securities or the Registrable Securities
owned by other Stockholders and specifying the intended method or methods of
disposition thereof (a "Demand Request"), the Company will, as promptly as
reasonably practicable but in no event later than 20 days after such request,
give written notice of such requested registration to all registered holders of
Registrable Securities who would be entitled to participate in such
registration, and thereupon the Company will, subject to the terms of this
Agreement, use its best efforts to effect the registration under the Securities
Act of:

                         (i)  the Registrable Securities which the Company has
          been so requested to register by such Initiating Holder (on its own
          and/or on behalf of the other Stockholders) for disposition in
          accordance with the intended method or methods of disposition stated
          in such request;

                         (ii) all other Registrable Securities the holders of
          which shall have made a written request to the Company for
          registration thereof within 30 days after the giving of such written
          notice by the Company (which request shall specify the intended method
          or methods of disposition of such Registrable Securities);

 
                         (iii) all shares of Common Stock which the Company may
          elect to register in connection with the offering of Registrable
          Securities pursuant to this section 2.1; and

                         (iv)  all shares of Common Stock which the Company may
          be required to register in connection with "piggyback" or incidental
          registration rights granted to any other Person;

all to the extent requisite to permit the disposition (in accordance with the
intended method or methods of distribution specified in the Demand Request) of
the Registrable Securities and the additional shares of Common Stock, if any, so
to be registered, provided, however, that each such Demand Request shall be for
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not less than 400,000 shares of Common Stock.  Subject to the provisions of
section 2.1(d), each Initiating Holder (on its own and/or on behalf of the other
Stockholders) will have the right pursuant to this section 2.1(a) to make one
Demand Request (i.e., an aggregate of two Demand Requests).

          Without limiting the generality of the foregoing, an Initiating Holder
shall have the right to request registration pursuant to this section 2.1 and
specify that one of the methods of disposition of Registrable Securities shall
be a block trade or trades involving Registrable Securities held by such
Initiating Holder and/or other Stockholders and that, in connection therewith,
the Company shall file with the Commission a registration statement under Rule
415 covering all of the Registrable Securities to be sold in the block trade or
trades.  In such case, the Company shall file an appropriate shelf registration
statement with the Commission as promptly as reasonably practicable and in
accordance with the provisions of section 2.3.  Subject to the provisions of
section 2.1(d), any shelf registration which involves a block trade or block
trades as an intended method of disposition, whether or not any such block trade
is made, shall be considered as the exercise of one of the two Demand Requests
permitted by this section 2.1(a).

          Notwithstanding anything herein to the contrary, it is understood and
agreed that an Initiating Holder may at any time on or after the earlier of (i)
30 days prior to the date on which it is agreed by the parties that the
restricted period under Accounting Series Release No. 135 would expire and (ii)
October 1, 1998 (the "Commencement Date") make a Demand Request for registration
pursuant to this section 2.1(a) and, in the event an Initiating Holder makes
such a request, the Company shall use its best efforts to file a registration
statement with the Commission with respect to such request not later than the
thirtieth day following such request.

          (b) Registration Statement Form.  Registrations under this section 2.1
              ---------------------------                                       
shall be on such appropriate registration form of the Commission (i) as shall be
selected by the Company and, as shall be reasonably acceptable to the Initiating

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Holder of the Registrable Securities so to be registered and (ii) as shall
permit the disposition of such Registrable Securities in accordance with the
intended method or methods of disposition specified in the request for such
registration.

          (c) Expenses.  The Company will pay all Registration Expenses in
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connection with any registration requested pursuant to this section 2.1
(including any registration deemed not to be "effected" under section 2.1).

          (d) Effective Registration Statement.  A registration requested
              --------------------------------                           
pursuant to this section 2.1 shall not be deemed to have been effected (and
therefore not requested for purposes of the limitations in section 2.1(a) on the
number of requests for registration that can be made pursuant to section 2.1(a))
(i) unless a registration statement with respect thereto has become effective,
provided that a registration which does not become effective after the Company
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has filed a registration statement with respect thereto solely by reason of the
refusal to proceed of the Initiating Holder (other than a refusal to proceed
based upon the advice of counsel relating to a matter with respect to the
Company) shall be deemed to have been effected by the Company at the request of
the Initiating Holder unless the Initiating Holder shall have elected to pay all
Registration Expenses in connection with such registration, (ii) if, after it
has become effective, such registration becomes subject to any stop order,
injunction or other order or requirement of the Commission or other governmental
agency or court for any reason, or (iii) if the conditions to closing specified
in the purchase agreement or underwriting agreement entered into in connection
with such registration are not satisfied, other than by reason of some act or
omission by the Initiating Holder or any other holder of Registrable Securities.

          (e) Selection of Underwriters.  If a requested registration pursuant
              -------------------------                                       
to this section 2.1 involves an underwritten offering, the underwriter or
underwriters thereof shall be selected by the Initiating Holder from a list of
underwriters to be agreed upon by the Initiating Holder and the Company.

          (f) Priority in Requested Registrations.  If a requested registration
              -----------------------------------                              
pursuant to this section 2.1 involves an underwritten offering, and the managing
underwriter shall advise the Company in writing (with a copy to each holder of
Registrable Securities requesting registration) that, in its opinion, the number
of securities requested to be included in such registration (including
securities of the Company which are not Registrable Securities) exceeds the
number which can be sold in such offering within a price range acceptable to the
holders of a majority of the Registrable Securities requested to be included in
such registration, the Company will include in such registration, to the extent
of the number which the Company is so advised can be sold in such offering, (i)
first, Registrable Securities requested to be included in such registration by
the Initiating Holder, (ii) second, Registrable Securities requested to be
included in 

                                      -3-

 
such registration by any other holder of Registrable Securities, pro rata among
                                                                 --- ----
such other holders requesting such registration on the basis of the number of
such securities requested to be included by such holders and (iii) third,
subject to section 2.1(a) hereof, securities the Company proposes to sell and
other securities of the Company included in such registration by other holders
who may have "piggyback" or incidental registration rights.

          (g) Delay Periods.  The Company shall be entitled to postpone the
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filing of any registration statement otherwise required to be prepared and filed
by the Company pursuant to this section 2.1, or suspend the use of any effective
registration statement under this section 2.1, for a reasonable period of time,
but not in excess of 90 days (a "Delay Period"), if (i) such postponement or
suspension is required by applicable law arising from events outside of the
control of the Company or (ii) any senior executive officer of the Company
determines that in such senior executive officer's reasonable good faith
judgment the registration and distribution of the Registrable Securities covered
or to be covered by such registration statement would materially interfere with
any pending material financing, acquisition, corporate reorganization, business
combination, joint venture, strategic alliance, commercial alliance or customer
contract involving the Company or any of its subsidiaries or would require
premature disclosure thereof and promptly gives the Initiating Holder written
notice of such determination, and an approximation of the period of the
anticipated delay; provided, however, that (i) the aggregate number of days
included in all Delay Periods during any consecutive 12 months shall not exceed
the aggregate of 180 days and (ii) a period of at least 90 days shall elapse
between the termination of any Delay Period and the commencement of the
immediately succeeding Delay Period.  Immediately upon receipt of a written
notice of suspension, each holder of Registrable Securities shall cease all
disposition efforts with respect to Registrable Securities held by such holder.
If the Company shall so postpone the filing of a registration statement, the
Holders of Registrable Shares to be registered shall automatically be deemed to
have withdrawn the request for registration and such request shall not be
counted for purposes of determining the number of Demand Requests for
registration to which the Initiating Holder of Registrable Shares is entitled
pursuant to this section 2.1.  The time period for which the Company is required
to maintain the effectiveness of any registration statement shall be extended by
the aggregate Delay Periods during such registration.  The Company shall not be
entitled to initiate a Delay Period unless it shall (A) to the extent permitted
by agreements with other security holders of the Company, concurrently prohibit
sales by such other security holders under registration statements covering
securities held by such other security holders and (B) in the case of a delay
arising as a result of premature disclosure, in accordance with the Company's
policies from time to time in effect, forbid purchases and sales in the open
market by senior executives of the Company.  Notwithstanding the foregoing, in
the case of a Demand Request made within 15 days 

                                      -4-

 
from and including the Commencement Date (and, if the filing of the registration
statement is postponed as provided in this sentence, in the case of any Demand
Request made in substitution for such Demand Request until a registration
statement has been filed pursuant to this Section 2.1), (i) the Company shall
only be entitled to exercise its postponement rights under this paragraph (g) by
reason of a pending material acquisition, corporate reorganization, business
combination, joint venture, strategic alliance, commercial alliance or customer
contract (but not by reason of a pending material financing transaction)
involving the Company or any of its subsidiaries or if required by applicable
law arising from events outside of the control of the Company; provided,
                                                               --------
however, in the case of a pending material joint venture, strategic alliance,
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commercial alliance or customer contract the applicable Delay Period shall be no
longer than fifty (50) days, and, (ii) for a period of 60 days following the
filing with the Commission of the registration statement relating to the
Registrable Securities covered by such Demand Request, the Company shall not be
entitled to exercise its suspension rights under this paragraph (g), except as
required by applicable law arising from events outside of the control of the
Company. In addition, in the case of a Demand Request other than a Demand
Request described in the preceding sentence, for a period of 60 days following
the filing with the Commission of the registration statement relating to the
Registrable Securities covered by such Demand Request, the Company shall only be
entitled to exercise its suspension rights under this paragraph (g) by reason of
a pending material acquisition, corporate reorganization, business combination,
joint venture, strategic alliance, commercial alliance or customer contract (but
not by reason of a pending material financing transaction) involving the Company
or any of its subsidiaries or if required by applicable law arising from events
outside of the control of the Company.

               2.2  Incidental Registration.
                    ----------------------- 

               (a)  Right to Include Registrable Securities. If the Company at
                    ---------------------------------------
any time proposes to register any of its shares of Common Stock (other than in
connection with a registration of securities which are convertible or
exchangeable into Common Stock) under the Securities Act (other than by a
registration on Form S-4 or S-8, or any successor or similar forms and other
than pursuant to section 2.1), whether or not for sale for its own account, it
will each such time give prompt written notice to all holders of Registrable
Securities of its intention to do so and of such holders' rights under this
section 2.2. Upon the written request of any such holder made within 30 days
after the receipt of any such notice (which request shall specify the
Registrable Securities intended to be disposed of by such holder and the
intended method or methods of disposition thereof), the Company will, subject to
the terms of this Agreement, use its best efforts to effect the registration
under the Securities Act of all Registrable Securities which the Company has
been so requested to register by the holders thereof, to the extent requisite to
permit the disposition (in accordance with the intended method or methods of
distribution thereof specified in the requests of such holders) of the
Registrable Securities

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so to be registered, by inclusion of such Registrable Securities in the
registration statement which covers the securities which the Company proposes to
register; provided that if, at any time after giving written notice of its
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intention to register any securities and prior to the effective date of the
registration statement filed in connection with such registration, the Company
shall determine for any reason either not to register or to delay registration
of such securities, the Company may, at its election, give written notice of
such determination to each holder of Registrable Securities and, thereupon, (i)
in the case of a determination not to register, shall be relieved of its
obligation to register any Registrable Securities in connection with such
registration (but not from its obligation to pay the Registration Expenses in
connection therewith), without prejudice, however, to the rights of any holder
or holders of Registrable Securities entitled to do so to request that such
registration be effected as a registration under section 2.1, and (ii) in the
case of a determination to delay registering, shall be permitted to delay
registering any Registrable Securities, for the same period as the delay in
registering such other securities. No registration effected under this section
2.2 shall relieve the Company of its obligation to effect any registration upon
request under section 2.1, nor shall any such registration hereunder be deemed
to have been effected pursuant to section 2.1. The Company will pay all
Registration Expenses in connection with each registration of Registrable
Securities requested pursuant to this section 2.2, and each holder whose
Registrable Securities are included in a registration requested pursuant to this
section 2.2 will pay any underwriting discounts and commissions and fees of such
holder's counsel in connection therewith.

          (b) Priority in Incidental Registrations.  If (i) a registration
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pursuant to this section 2.2 involves an underwritten offering of the securities
so being registered, whether or not for sale for the account of the Company, to
be distributed (on a firm commitment basis) by or through one or more
underwriters of recognized standing under underwriting terms appropriate for
such a transaction, and (ii) the managing underwriter of such underwritten
offering shall inform the Company and holders of the Registrable Securities
requesting such registration by letter of its belief that the number of
securities requested to be included in such registration exceeds the number
which can be sold in (or during the time of) such offering, then the Company
will include in such registration:

                    (i)   first, all the securities the Company proposes to sell
          for its own account,

                    (ii)  second, all securities of any other holder who has
          made a demand for registration,

                    (iii) third, all securities of any holder who is entitled to
          incidental registration rights under the registration rights agreement
          dated 

                                      -6-

 
          as of September 22, 1997 by and between the Company and 399 Venture
          Partners, Inc.(the Amerisource Agreement"), and

                    (iv) fourth, to the extent that the number of securities
          which the Company and any such other holders proposed to include
          pursuant to clauses (i), (ii) and (iii) is less than the number of
          securities which the Company has been advised can be sold in such
          offering, the number of (x) such Registrable Securities requested to
          be included in such registration by the holders of Registrable
          Securities pursuant to section 2.2(a) hereof and (y) other equity
          securities of the Company requested to be included in such
          registration by holders of such securities who are entitled to
          incidental registration rights under any other registration rights
          agreements with the Company shall be allocated pro rata among all such
                                                         --- ----               
          holders on the basis of the relative number of Registrable Securities
          and other equity securities each such holder has requested to be
          included in such registration.

               2.3  Registration Procedures. If and whenever the Company is
                    -----------------------
required to effect the registration of any Registrable Securities under the
Securities Act as provided in sections 2.1 and 2.2, the Company shall, as
expeditiously as reasonably possible:

                    (i)  prepare and file with the Commission the requisite
          registration statement to effect such registration (including such
          audited financial statements as may be required by the Securities Act
          or the rules and regulations promulgated thereunder) and thereafter
          cause such registration statement to become and remain effective for a
          period of at least 120 days, provided however that the Company may
                                       --------                             
          discontinue any registration of its securities which are not
          Registrable Securities (and, under the circumstances specified in
          section 2.2(a), its securities which are Registrable Securities) at
          any time prior to the effective date of the registration statement
          relating thereto;

                    (ii) prepare and file with the Commission such amendments
          and supplements to such registration statement and the prospectus used
          in connection therewith as may be necessary to keep such registration
          statement effective for a period of at least 120 days and to comply
          with the provisions of the Securities Act with respect to the
          disposition of all securities covered by such registration statement
          until the earlier of such time as all of such securities have been
          disposed of in accordance with the intended methods of disposition by
          the seller or sellers 

                                      -7-

 
          thereof set forth in such registration statement or such other time as
          is required by the Securities Act;

                    (iii) furnish to each seller of Registrable Securities
          covered by such registration statement and each underwriter, if any,
          of the securities being sold by such seller such number of conformed
          copies of such registration statement and of each such amendment and
          supplement thereto (in each case including all exhibits), such number
          of copies of the prospectus contained in such registration statement
          (including each preliminary prospectus and any summary prospectus) and
          any other prospectus filed pursuant to Rule 424 under the Securities
          Act, in conformity with the requirements of the Securities Act, and
          such other documents, as such seller and underwriter, if any, may
          reasonably request;

                    (iv)  use its best efforts to register or qualify all
          Registrable Securities and other securities covered by such
          registration statement under such other state securities laws or blue
          sky laws of such jurisdictions as any seller thereof and any
          underwriter of the securities being sold by such seller shall
          reasonably request, to keep such registrations or qualifications in
          effect for so long as such registration statement remains in effect,
          and take any other action which may be reasonably necessary or
          advisable to enable such seller and underwriter to consummate the
          disposition in such jurisdictions of the securities owned by such
          seller, except that the Company shall not for any such purpose be
          required to qualify generally to do business as a foreign corporation
          in any jurisdiction wherein it would not but for the requirements of
          this subsection (iv) be obligated to be so qualified or to consent to
          general service of process in any such jurisdiction;

                    (v)   furnish to each seller of Registrable Securities a
          signed counterpart, addressed to such seller and the underwriters, if
          any, of:

                          (X)  an opinion of counsel for the Company (which
               shall be outside counsel if outside counsel is rendering such
               opinion in the transaction and otherwise may be the Company's
               inside counsel), dated the effective date of such registration
               statement (or, if such registration includes an underwritten
               public offering, an opinion dated the date of the closing under
               the underwriting agreement), customary for a transaction of such
               type, and

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                              (Y) a "comfort" letter (or, in the case of any
                    such Person which does not satisfy the conditions for
                    receipt of a "comfort" letter specified in Statement on
                    Auditing Standards No. 72, as amended by Statements on
                    Auditing Standards Nos. 76 and 86, an "agreed upon
                    procedures" letter), dated the effective date of such
                    registration statement (and, if such registration includes
                    an underwritten public offering, a letter of like kind dated
                    the date of the closing under the underwriting agreement),
                    signed by the independent public accountants who have
                    certified the Company's financial statements included in
                    such registration statement, covering substantially the same
                    matters with respect to such registration statement (and the
                    prospectus included therein) and, in the case of the
                    accountants' letter, with respect to events subsequent to
                    the date of such financial statements, as are customarily
                    covered in opinions of issuer's counsel and in accountants'
                    letters delivered to the underwriters in underwritten public
                    offerings of securities (with, in the case of an "agreed
                    upon procedures" letter, such modifications or deletions as
                    may be required under Statement on Auditing Standards No.
                    75) and, in the case of the accountants' letter, such other
                    financial matters customarily covered in a transaction of
                    such type;

                         (vi) notify the holders of Registrable Securities and
          the managing underwriter or underwriters, if any, promptly:

                              (V) when the registration statement, the
                    prospectus or any prospectus supplement related thereto or
                    post-effective amendment to the registration statement has
                    been filed, and, with respect to the registration statement
                    or any post-effective amendment thereto, when the same has
                    become effective:

                              (W) of any request by the Commission for
                    amendments or supplements to the registration statement or
                    the prospectus or for additional information;

                              (X) of the issuance by the Commission of any stop
                    order suspending the effectiveness of the registration
                    statement or the initiation of any proceedings by any Person
                    for that purpose;

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                                (Y) if at any time the representations and
                    warranties of the Company made as contemplated by section
                    2.4 below cease to be true and correct; and

                                (Z) of the receipt by the Company of any
                    notification with respect to the suspension of the
                    qualification of any Registrable Securities for sale under
                    the securities or blue sky laws of any jurisdiction or the
                    initiation or threat of any proceeding for such purpose;

                         (vii)  notify each seller of Registrable Securities
          covered by such registration statement, at any time when a prospectus
          relating thereto is required to be delivered under the Securities Act,
          upon the Company's discovery that, or upon the happening of any event
          as a result of which, the prospectus included in such registration
          statement, as then in effect, includes an untrue statement of a
          material fact or omits to state any material fact required to be
          stated therein or necessary to make the statements therein not
          misleading in the light of the circumstances under which they were
          made, and at the request of any such seller promptly prepare and
          furnish to such seller and each underwriter, if any, a reasonable
          number of copies of a supplement to or an amendment of such prospectus
          as may be necessary so that, as thereafter delivered to the purchasers
          of such securities, such prospectus shall not include 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 not
          misleading in the light of the circumstances under which they were
          made;

                         (viii) make every reasonable effort to obtain the
          withdrawal of any order suspending the effectiveness of the
          registration statement as promptly as possible;

                         (ix)   otherwise use its best efforts to comply with
          all applicable rules and regulations of the Commission, and, if
          required, make available to its security holders, as soon as
          reasonably practicable, an earnings statement covering the period of
          at least twelve months, but not more than eighteen months, beginning
          with the first day of the Company's first full calendar quarter after
          the effective date of such registration statement, which earnings
          statement shall satisfy the provisions of Section 11(a) of the
          Securities Act and Rule 158 thereunder, and use its best efforts to
          furnish to each such seller at least one business day prior to the
          filing thereof a copy of any amendment or supplement to such
          registration statement or prospectus and shall not file any thereof to
          which any such 

                                      -10-

 
          seller shall have reasonably objected on the grounds that such
          amendment or supplement does not comply in all material respects with
          the requirements of the Securities Act or of the rules or regulations
          thereunder;

                         (x)  provide and cause to be maintained a transfer
          agent and registrar for all Registrable Securities covered by such
          registration statement from and after a date not later than the
          effective date of such registration statement; and

                         (xi) use its best efforts to list all Registrable
          Securities covered by such registration statement on any securities
          exchange on which any of the securities of the same class as the
          Registrable Securities are then listed.

          The Company will not file any registration statement or amendment
thereto or any prospectus or any supplement thereto to which the holders of at
least a majority of the Registrable Securities covered by such registration
statement or the underwriter or underwriters, if any, shall reasonably object.

          The Company may require each seller of Registrable Securities as to
which any registration is being effected to furnish the Company such information
regarding such seller and the distribution of such securities as the Company may
from time to time reasonably request in writing.

          Each holder of Registrable Securities agrees by acquisition of such
Registrable Securities that, upon receipt of any notice from the Company of the
occurrence of any event of the kind described in paragraph (vii) of this section
2.3, such holder will forthwith discontinue such holder's disposition of
Registrable Securities pursuant to the registration statement relating to such
Registrable Securities until such holder's receipt of the copies of the
supplemented or amended prospectus contemplated by paragraph (vii) of this
section 2.3 and, if so directed by the Company, will deliver to the Company (at
the Company's expense) all copies, other than permanent file copies, then in
such holder's possession of the prospectus relating to such Registrable
Securities current at the time of receipt of such notice.  In the event the
Company shall give any such notice, the period mentioned in paragraph (ii) of
this section 2.3 shall be extended by the length of the period from and
including the date when each seller of any Registrable Securities covered by
such registration statement shall have received such notice to the date on which
each such seller has received the copies of the supplemented or amended
prospectus contemplated by paragraph (vii) of this section 2.3.

               2.4. Underwritten Offerings:
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               (a)  Requested Underwritten Offerings.  If requested by the
                    --------------------------------                      
underwriters for any underwritten offering by holders of Registrable Securities
pursuant to a registration requested under section 2.1, the Company will enter
into an underwriting or similar agreement with such underwriters for such
offering, such agreement to be reasonably satisfactory in substance and form to
the Company, each such holder and the underwriters, and to contain such
representations and warranties by the Company and such other terms as are
generally prevailing in agreements of this type, including, without limitation,
indemnities to the effect and to the extent provided in section 2.6.  The
holders of the Registrable Securities will cooperate with the Company in the
negotiation of the underwriting or similar agreement and will give consideration
to the reasonable suggestions of the Company regarding the form thereof,
provided that nothing herein contained shall diminish the foregoing obligations
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of the Company.  The holders of Registrable Securities to be distributed by such
underwriters shall be parties to such underwriting agreement and may, at their
option, require that any or all of the representations and warranties by, and
the other agreements on the part of, the Company to and for the benefit of such
underwriters shall also be made to and for the benefit of such holders of
Registrable Securities and that any or all of the conditions precedent to the
obligations of such underwriters under such underwriting agreement be conditions
precedent to the obligations of such holders of Registrable Securities.  No
underwriting or similar agreement shall require any holder of Registrable
Securities to make any representations or warranties to or agreements with the
Company or the underwriters other than representations and warranties or
agreements regarding such holder, such holder's Registrable Securities and such
holder's intended method or methods of distribution and any other representation
required by law or to make any agreements with the Company or the underwriters
with respect to indemnification of any Person or the contribution obligations of
any Person that would impose any obligation which is broader than the indemnity
furnished by such holder pursuant to the provisions of section 2.6.  In
addition, the holders of Registrable Securities shall cooperate with the Company
in an effort to provide that any such agreement will contain a provision
modifying the indemnification of the underwriter to the effect that the Company
will not be liable to any Person who participates as an underwriter in the
offering or sale of Registrable Securities with respect to any preliminary
prospectus, to the extent that any such loss, claim, damage or liability of such
underwriter results from such underwriter having sold Registrable Securities to
a person to whom there was not sent or given, at or prior to the written
confirmation of such sale, a copy of the final prospectus, if the Company has
previously furnished copies thereof to such underwriter and such final
prospectus as then amended or supplemented, has corrected any such misstatement
or omission.

               (b)  Incidental Underwritten Offerings. If the Company at any
                    ---------------------------------
time proposes to register any of its securities under the Securities Act as
contemplated by section 2.2 and such securities are to be distributed by or
through one or more

                                      -12-

 
underwriters, the Company will, if requested by any holder of Registrable
Securities as provided in section 2.2 and subject to the provisions of section
2.2(b), use its best efforts to arrange for such underwriters to include all the
Registrable Securities to be offered and sold by such holder among the
securities to be distributed by such underwriters. The holders of Registrable
Securities to be distributed by such underwriters shall be parties to the
underwriting agreement between the Company and such underwriters and may, at
their option, require that any or all of the representations and warranties by,
and the other agreements on the part of, the Company to and for the benefit of
such underwriters shall also be made to and for the benefit of such holders of
Registrable Securities and that any or all of the conditions precedent to the
obligations of such underwriters under such underwriting agreement be conditions
precedent to the obligations of such holders of Registrable Securities. Any such
holder of Registrable Securities shall not be required to make any
representations or warranties to or agreements with the Company or the
underwriters other than representations, warranties or agreements regarding such
holder, such holder's Registrable Securities and such holder's intended method
or methods of distribution and any other representation required by law or to
make any agreements with the Company or the underwriters with respect to
indemnification of any Person or the contribution obligations of any Person that
would impose any obligation which is broader than the indemnity furnished by
such holder pursuant to the provisions of section 2.6. In addition, the holders
of Registrable Securities shall cooperate with the Company in an effort to
provide that any such agreement will contain a provision modifying the
indemnification of the underwriter to the effect that the Company will not be
liable to any Person who participates as an underwriter in the offering or sale
of Registrable Securities with respect to any preliminary prospectus, to the
extent that any such loss, claim, damage or liability of such underwriter
results from such underwriter having sold Registrable Securities to a person to
whom there was not sent or given, at or prior to the written confirmation of
such sale, a copy of the final prospectus, if the Company has previously
furnished copies thereof to such underwriter and such final prospectus as then
amended or supplemented, has corrected any such misstatement or omission.

               (c)  Holdback Agreements.
                    ------------------- 

                         (i)  Each holder of Registrable Securities agrees by
          acquisition of such Registrable Securities, if and to the extent so
          required by the managing underwriter, not to sell, make any short sale
          of, loan, grant any option for the purchase of, effect any sale or
          distribution of or otherwise dispose of any securities of the Company,
          during the 7 days prior to and the 90 days after any underwritten
          registration pursuant to section 2.1 or 2.2 has become effective,
          except as part of such underwritten registration, whether or not such
          holder participates in such registration, provided that the foregoing
                                                    --------                   
          restrictions shall not apply (x) with regard to any Stockholder in a
          distribution of Registrable Securities to its partners or to the
          transfer to any 

                                      -13-

 
          Affiliate of such Persons, or to any bona fide pledge of such
          Registrable Securities, provided that such Affiliate or other
          transferee and/or lender or creditor acknowledges in writing that it
          is bound by the provisions of this section 2.4(c) and (y) unless the
          senior executive officers and directors of the Company agree to be so
          restricted. Each holder of Registrable Securities agrees that the
          Company may instruct its transfer agent to place stop transfer
          notations in its records to enforce this section 2.4(c).

                         (ii) The Company agrees (X) if so required by the
          managing underwriter not to sell, make any short sale of, loan, grant
          any option for the purchase of, effect any sale or distribution of or
          otherwise dispose of its equity securities or securities convertible
          into or exchangeable or exercisable for any of such securities during
          the seven days prior to and the 90 days after any underwritten
          registration pursuant to section 2.1 or 2.2 has become effective,
          except as part of such underwritten registration and except pursuant
          to registrations on Form S-4, S-8, or any successor or similar forms
          thereto, and (Y) to cause each holder of its securities purchased from
          the Company at any time after the date of this Agreement (other than
          in a public offering) to agree not to sell, make any short sale of,
          loan, grant any option for the purchase of, effect any sale or
          distribution of or otherwise dispose of such securities during such
          periods.

               (d)  Participation in Underwritten Offerings.  No Person may
                    ---------------------------------------                
participate in any underwritten offering hereunder unless such Person (i) agrees
to sell such Person's securities on the basis provided in any underwriting
arrangements approved, subject to the terms and conditions hereof, by the
Company and the holders of a majority of Registrable Securities to be included
in such underwritten offering and the Initiating Holder, if applicable, and (ii)
completes and executes all questionnaires, indemnities, underwriting agreements
and other documents (other than powers of attorney) required under the terms of
such underwriting arrangements.  Notwithstanding the foregoing, no underwriting
agreement (or other agreement in connection with such offering) shall require
any holder of Registrable Securities to make any representations or warranties
to or agreements with the Company or the underwriters other than representations
and warranties regarding such holder, such holder's Registrable Securities and
such holder's intended method or methods of distribution and any other
representation required by law or to make any agreements with the Company or the
underwriters with respect to indemnification of any Person or the contribution
obligations of any Person that would impose any obligation which is broader than
the indemnity furnished by such holder pursuant to the provisions of section
2.6.

               2.5  Preparation: Reasonable Investigation. In connection with
                    --------------------------------------
the preparation and filing of each registration statement under the Securities
Act pursuant

                                      -14-

 
to this Agreement, the Company will give the holders of Registrable Securities
registered under such registration statement, their underwriters, if any, and
their respective counsel and accountants, the opportunity to participate in the
preparation of such registration statement, each prospectus included therein or
filed with the Commission, and each amendment thereof or supplement thereto, and
will give each of them such reasonable access during normal business hours to
its books and records and such opportunities to discuss the business of the
Company with its officers and the independent public accountants who have
certified its financial statements as shall be necessary, in the opinion of such
holders' and such underwriters' respective counsel, to conduct a reasonable
investigation within the meaning of the Securities Act.

               2.6  Indemnification.
                    --------------- 

               (a)  Indemnification by the Company. In the event of any
                    ------------------------------
registration of any securities of the Company under the Securities Act pursuant
to section 2.1 or 2.2, the Company will, and hereby does agree to, indemnify and
hold harmless the holder of any Registrable Securities covered by such
registration statement and its partners, if any, its and their respective
directors, officers, partners, agents and Affiliates, each other Person who
participates as an underwriter in the offering or sale of such securities and
each other Person, if any, who controls such holder or any such underwriter
within the meaning of the Securities Act, against any losses, claims, damages or
liabilities, joint or several, to which such holder or partner thereof or any
such director or officer or partner or agent or Affiliate or underwriter or
controlling person may become subject under the Securities Act or otherwise,
insofar as such losses, claims, damages or liabilities (or actions or
proceedings, whether commenced or threatened, in respect thereof) arise out of
or are based upon any untrue statement or alleged untrue statement of any
material fact contained in any registration statement under which such
securities were registered under the Securities Act, any preliminary prospectus,
final prospectus or summary prospectus contained therein, or any amendment or
supplement thereto, or 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, and the Company will reimburse such holder, its
respective partners and each such director, officer, partner, agent, Affiliate,
underwriter and controlling person for any legal or any other expenses
reasonably incurred by them in connection with investigating or defending any
such loss, claim, liability, action or proceeding, provided, that the Company
                                                   --------
shall not be liable in any such case to the extent that any such loss, claim,
damage, liability (or action or proceeding in respect thereof) or expense arises
out of or is based upon an untrue statement or alleged untrue statement or
omission or alleged omission made in such registration statement, any such
preliminary prospectus, final prospectus, summary prospectus, amendment or
supplement in reliance upon and in conformity with written information furnished
to the Company through an instrument duly executed by such holder, specifically
stating that it is for use in the preparation thereof. Such indemnity

                                      -15-

 
shall remain in full force and effect regardless of any investigation made by or
on behalf of such holder or partner thereof or any such director, officer,
partner, agent, Affiliate, underwriter or controlling person and shall survive
the transfer of such securities by such holder. The indemnity agreement
contained in this section 2.6 shall not apply to amounts paid in settlement of
any such loss, claim, damage, liability, action or proceeding if such settlement
is effected without the consent of the Company.

               (b)  Indemnification by the Sellers. The Company may require, as
                    ------------------------------
a condition to including any Registrable Securities in any registration
statement filed pursuant to section 2.3, that the Company shall have received an
undertaking reasonably satisfactory to it from the prospective seller of such
Registrable Securities, to indemnify severally and hold harmless (in the same
manner and to the same extent as set forth in subsection (a) of this section
2.6) the Company, each director of the Company, each officer of the Company and
each other person, if any, who controls the Company within the meaning of the
Securities Act, with respect to any statement or alleged statement in or
omission or alleged omission from such registration statement, any preliminary
prospectus, final prospectus or summary prospectus contained therein, or any
amendment or supplement thereto, if such statement or alleged statement or
omission or alleged omission was made in reliance upon and in conformity with
written information furnished to the Company through an instrument duly executed
by such seller specifically stating that it is for use in the preparation of
such registration statement, preliminary prospectus, final prospectus, summary
prospectus, amendment or supplement. Any such indemnity shall remain in full
force and effect, regardless of any investigation made by or on behalf of the
Company or any such director, officer or controlling person and shall survive
the transfer of such securities by such seller. The indemnity agreement provided
for in this section 2.6(b) shall not apply to amounts paid in settlement of any
such loss, claim, damage, liability, action or proceeding if such settlement is
effected without the consent of such seller (which consent shall not be
unreasonably withheld). The parties hereto hereby acknowledge and agree that,
unless otherwise expressly agreed to in writing by holders of Registrable
Securities to the contrary, for all purposes of this Agreement the only
information furnished or to be furnished to the Company for use in any
registration statement, any preliminary prospectus, final prospectus or summary
prospectus contained therein, or any amendment or supplement thereto are
statements specifically relating to (i) the beneficial ownership of shares of
Common Stock by such holders and its Affiliates, (ii) the name and address of
such holder and (iii) the method or methods of distribution of such holders. The
indemnity provided for under this section 2.6(b) shall be limited in amount to
the net amount of proceeds actually received by such seller from the sale of
Registrable Securities pursuant to such registration statement.

               (c)  Notices of Claims, etc. Promptly after receipt by an
                    ----------------------
indemnified party of notice of the commencement of any action or proceeding
involving a claim referred to in the preceding subsections of this section 2.6,
such indemnified party

                                      -16-

 
will, if a claim in respect thereof is to be made against an indemnifying party,
give written notice to the latter of the commencement of such action, provided
                                                                      --------
that the failure of any indemnified party to give notice as provided herein
shall not relieve the indemnifying party of its obligations under the preceding
subsections of this section 2.6, except to the extent that the indemnifying
party is actually prejudiced by such failure to give notice. In case any such
action is brought against an indemnified party, unless in such indemnified
party's reasonable judgment a conflict of interest between such indemnified and
indemnifying parties may exist in respect of such claim, the indemnifying party
shall be entitled to participate in and to assume the defense thereof, jointly
with any other indemnifying party similarly notified, to the extent that the
indemnifying party may wish, with counsel reasonably satisfactory to such
indemnified party, and after notice from the indemnifying party to such
indemnified party of its election so to assume the defense thereof, the
indemnifying party shall not be liable to such indemnified party for any legal
or other expenses subsequently incurred by the latter in connection with the
defense thereof other than reasonable costs of investigation. No indemnifying
party shall, without the consent of the indemnified party, consent to entry of
any judgment or enter into any settlement of any such action which does not
include as an unconditional term thereof the giving by the claimant or plaintiff
to such indemnified party of a release from all liability, or a covenant not to
sue, in respect to such claim or litigation. No indemnified party shall consent
to entry of any judgment or enter into any settlement of any such action the
defense of which has been assumed by an indemnifying party without the consent
of such indemnifying party.

               (d)  Indemnification Payments. The indemnification required by
                    ------------------------
this section 2.6 shall be made by periodic payments of the amount thereof during
the course of the investigation or defense, as and when bills are received or
expense, loss, damage or liability is incurred.

               (e)  Contribution.  If the indemnification provided for in the
                    ------------                                             
preceding subsections of this section 2.6 is unavailable to an indemnified party
in respect of any expense, loss, claim, damage or liability 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 expense, loss, claim, damage or liability in such proportion as
is appropriate to reflect the relative benefits and the relative fault of the
Company on the one hand and the holder or underwriter, as the case may be, on
the other in connection with the distribution of the Registrable Securities and
the statements or omissions which result in any expense, loss, damage or
liability, as well as any other relevant equitable considerations.  The relative
fault of the Company on the one hand and of the holder or underwriter, as the
case may be, on the other shall be determined by reference to, among other
things, whether the untrue or alleged untrue statement of a material fact or
omission to state a material fact relates to information supplied by the
Company, by the holder or by the underwriter and the parties' relative 

                                      -17-

 
intent, knowledge, access to information and opportunity to correct or prevent
such statement or omission.

          The Company and the holders of Registrable Securities agree that it
would not be just and equitable if contribution pursuant to this subsection (e)
were determined by pro rata allocation (even if the holders and any underwriters
                   --- ----                                                     
were treated as one entity for such purpose) or by any other method of
allocation that 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 and liabilities
referred to in the immediately preceding paragraph shall be deemed to include,
subject to the limitations set forth in the preceding sentence and subsection
(c) of this section 2.6, any legal or other expenses reasonably incurred by such
indemnified party in connection with investigating or defending any such action
or claim.

          Notwithstanding the provisions of this subsection (e), no holder of
Registrable Securities or underwriter shall be required to contribute any amount
in excess of the amount by which (i) in the case of any such holder the net
proceeds received by such holder from the sale of Registrable Securities or (ii)
in the case of an underwriter, the total price at which the Registrable
Securities purchased by it and distributed to the public were offered to the
public exceeds, in any such case, the amount of any damages that such holder or
underwriter has otherwise been required to pay by reason of such untrue or
alleged untrue statement or omission.  No Person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation.  No party shall be liable for contribution under
this section 2.6 except to the extent and under such circumstances as such party
would have been liable to indemnify under this section 2.6 if such
indemnification were enforceable under applicable law.

               2.7  Limitations on Registrations of Registrable Securities. The
                    ------------------------------------------------------
Company shall not be required to effect any registration of Registrable
Securities pursuant to Section 2.1 or 2.2 hereof (other than with respect to a
registration pursuant to Section 2.1 of Registrable Securities of an Initiating
Holder) if it shall deliver (i) to the requesting holder of Registrable
Securities an opinion of counsel (which opinion and counsel shall be reasonably
satisfactory to such Initiating Holder, or other requesting holder of
Registrable Securities, if applicable) to the effect that all Registrable
Securities held by such Initiating Holder, or other requesting holder of
Registrable Securities, if applicable, may be sold immediately in the public
market without registration under the Securities Act and any applicable state
securities laws and (ii) to the Company's stock transfer agent a letter of
instruction removing any stop order and restrictive legends on such Registrable
Securities.

                                      -18-

 
               2.8  Restrictions Imposed by Amerisource Agreement. Each holder
                    ---------------------------------------------
of Registrable Securities agrees that, as required by Section 2.4(c) of the
Amerisource Agreement, notwithstanding any other provision of this Agreement,
such holder shall not sell, make any short sale of, loan, grant any option for
the purchase of, effect any public sale or distribution of or otherwise dispose
of any equity securities or securities convertible into or exchangeable or
exercisable for any of such securities during the seven days prior to and the 90
days after any underwritten registration pursuant to Section 2.1 (demand
requests) or 2.2 (incidental registration) of the Amerisource Agreement has
become effective, other than the right of such holder of Registrable Securities
to include Registrable Securities in such registration pursuant to Section 2.2
hereof; provided that the foregoing restrictions shall not apply (x) with regard
to any Stockholder in a distribution of Registrable Securities to its partners
or to the transfer to any Affiliate of such Persons, or to any bona fide pledge
of such Registrable Securities, provided that such Affiliate or other transferee
and/or lender or creditor acknowledges in writing that it is bound by the
provisions of this Section 2.8 and (y) unless the senior executive officers and
directors of the Company agree to be so restricted. Each holder of Registrable
Securities agrees that the Company may instruct its transfer agent to place stop
transfer notations in its records to enforce this Section 2.8.

          3.   Definitions. As used herein, unless the context otherwise
               -----------
requires, the following terms have the following respective meanings.

               Affiliate:  As defined in Rule 12b-2 promulgated under the
               ---------                                                 
               Exchange Act.

               Beneficially Own or Beneficial Ownership:  With respect to any
               -----------------   --------------------                      
               securities shall mean having "beneficial ownership" of such
               securities (as determined pursuant to Rule 13d-3 under the
               Exchange Act), including pursuant to any agreement, arrangement
               or understanding, whether or not in writing.  Without duplicative
               counting of the same securities by the same holder, securities
               Beneficially Owned by a person shall include securities
               Beneficially Owned by all Affiliates of such Person and all other
               Persons with whom such person would constitute a "group" within
               the meaning of Section 13 (d) of the Exchange Act and the rules
               promulgated thereunder.

               Commission:  The Securities and Exchange Commission or any other
               ----------                                                      
               Federal agency at the time administering the Securities Act.

               Common Stock:  As defined in section 1.
               ------------                           

                                      -19-

 
               Company:  As defined in the introductory paragraph of this
               -------                                                   
               Agreement.

               Delay Period:  As defined in section 2.1(g).
               ------------                                

               Demand Request:  As defined in section 2.1(a).
               --------------                                

               Effective Time:  As defined in the Merger Agreement.
               --------------                                      

               Exchange Act:  The Securities Exchange Act of 1934, or any
               ------------                                              
               similar Federal statute, and the rules and regulations of the
               Commission thereunder, all as the same shall be in effect at the
               time.  Reference to a particular section of the Securities
               Exchange Act of 1934 shall include a reference to the comparable
               Section, if any, of any such similar federal statute.

               Initiating Holder:  Either Premier Purchasing Partners, L.P. or
               -----------------                                              
               Welsh, Carson, Anderson & Stowe VII L.P.

               Merger Agreement:  As defined in section 1.
               ----------------                           

               Person:  A corporation, an association, a partnership, an
               ------                                                   
               organization, business, an individual, a governmental or
               political subdivision thereof or a governmental agency.

               Registrable Securities:  The Common Stock issued pursuant to the
               ----------------------                                          
               transactions contemplated by the Merger Agreement and any
               securities issued or issuable with respect to any Common Stock by
               way of stock dividend or stock split or in connection with a
               combination of shares, recapitalization, merger, consolidation or
               other reorganization or otherwise.  As to any particular
               Registrable Securities, once issued, such securities shall cease
               to be Registrable Securities when (a) a registration statement
               with respect to the sale of such securities shall have become
               effective under the Securities Act and such securities have been
               disposed of in accordance with such registration statement, (b)
               they shall have been distributed to the public pursuant to Rule
               144 (or any successor provision) under the Securities Act, (c) a
               disposition of all of them by the holder thereof shall not
               require registration or qualification of them under the
               Securities Act or shall be eligible for disposition under Rule
               144, or (d) they shall have ceased to be outstanding.

                                      -20-

 
               Registration Expenses:  All expenses incident to the Company's
               ---------------------                                         
               performance of or compliance with section 2, including, without
               limitation, all registration, filing and NASD fees, all stock
               exchange listing fees, all fees and expenses of complying with
               securities or blue sky laws, all word processing, duplicating and
               printing expenses, messenger and delivery expenses, the fees and
               disbursements of counsel for the Company and of its independent
               public accountants, including the expenses of any special audits
               or "cold comfort" letters required by or incident to such
               performance and compliance, and any fees and disbursements of
               underwriters customarily paid by issuers or sellers or
               securities, but excluding underwriting discounts and commissions
               and transfer taxes, if any.

               Securities Act:  The Securities Act of 1933, or any similar
               --------------                                             
               Federal statute, and the rules and regulations of the Commission
               thereunder, all as of the same shall be in effect at the time.
               References to a particular section of the Securities Act of 1933
               shall include a reference to the comparable Section, if any, of
               any such similar Federal statute.

               Transfer:  A transfer, sale, pledge, hypothecation, encumbrance,
               --------                                                        
               assignment or other conveyance or disposition except an
               assignment by operation of law.

          4.   Rule 144. The Company shall timely file the reports required to
               --------
be filed by it under the Securities Act and the Exchange Act (including but not
limited to the reports under sections 13 and 15(d) of the Exchange Act referred
to in subparagraph (c) of Rule 144 adopted by the Commission under the
Securities Act) and the rules and regulations adopted by the Commission
thereunder and will take such further action as any holder of Registrable
Securities may reasonably request, all to the extent required from time to time
to enable such holder to sell Registrable Securities without registration under
the Securities Act within the limitation of the exemptions provided by (a) Rule
144 under the Securities Act, as such Rule may be amended form time to time, or
(b) any similar rule or regulation hereafter adopted by the Commission. Upon the
request of any holder of Registrable Securities, the Company will (a) deliver to
such holder a written statement as to whether it has complied with the
requirements of this section 4 or (b) take such action as is necessary to allow
transfer of such Registrable Securities in accordance with the provisions of
Rule 144(k) (or any successor provision) under the Securities Act, including
without limitation, if necessary, the issuance of new certificates for such
Registrable Securities bearing a legend restricting further transfer.

                                      -21-

 
          5.  Amendments and Waivers. This Agreement may be amended and the
              ----------------------
Company may take any action herein prohibited, or omit to perform any act herein
required to be performed by it, only if the Company shall have obtained the
written consent to such amendment, action or omission to act, of the holder or
holders of more than 50% of the shares of Registrable Securities and in the case
of any such amendment, action or omission to act in respect of the first
sentence of Section 4, the written consent of each holder affected thereby. Each
holder of any Registrable Securities at the time or thereafter outstanding shall
be bound by any consent authorized by this section 5, whether or not such
Registrable Securities shall have been marked to indicate such consent.

          6.  Nominees for Beneficial Owners. In the event that any Registrable
              ------------------------------
Securities are held by a nominee for the beneficial owner thereof, the
beneficial owner thereof may, at its election, be treated as the holder of such
Registrable Securities for purposes of any request or other action by any holder
or holders of Registrable Securities pursuant to this Agreement or any
determination of any number or percentage of shares of Registrable Securities
held by any holder or holders of Registrable Securities contemplated by this
Agreement. If the beneficial owner of any Registrable Securities so elects, the
Company may require assurances reasonably satisfactory to it of such owner's
beneficial ownership of such Registrable Securities.

          7.  Notices. Except as otherwise provided in this Agreement, all
              -------
notices, requests and other communications to any Person provided for hereunder
shall be in writing and shall be given to such Person (a) in the case of any
Stockholder, addressed to such party care of Welsh, Carson, Anderson & Stowe,
320 Park Avenue, Suite 2500, New York, New York 10022 to the attention of Paul
B. Queally with a copy to Reboul, MacMurray, Hewitt, Maynard & Kristol, 45
Rockefeller Plaza, New York, New York 10111 to the attention of Othon Prounis,
Esq. and care of Premier, Inc., 12225 El Camino Real, San Diego, California
92130 to the attention of Bary G. Bailey with a copy to Neal, Gerber &
Eisenberg, Two North LaSalle Street, Chicago, Illinois 60602 to the attention of
Charles E. Gerber, Esq., or at such other address as such party shall have
furnished to the Company in writing, (b) in the case of any other holder of
Registrable Securities, at the address that such holder shall have furnished to
the Company in writing, or, until any such other holder so furnishes to the
Company an address, then to and at the address of the last holder of such
Registrable Securities who has furnished an address to the Company or (c) in the
case of the Company, at McKesson Corporation, One Post Street, San Francisco,
California 94104, to the attention of its General Counsel, or at such other
address, or to the attention of such other officer, as the Company shall have
furnished to each holder of Registrable Securities at the time outstanding. Each
such notice, request or other communication shall be effective (i) if given by
mail, on the second business day after such communication is deposited in the
mail with first class postage prepaid, addressed as aforesaid or (ii) if given
by any other means (including without limitation, by air courier), when
delivered at the address specified above,

                                      -22-

 
provided that any such notice, request or communication to any holder of
- ---------                                                               
Registrable Securities shall not be effective until received.

          8.  Assignment. This Agreement shall be binding upon and inure to the
              ----------
benefit of and be enforceable by the parties hereto and their respective
successors and assigns. No holder of Registrable Securities shall assign this
Agreement or any rights hereunder without the prior written consent of the
Company (which consent may be withheld for any reason in the sole discretion of
the Company), except that this Agreement and any rights hereunder may be
assigned by operation of law and may be assigned to any partner or Affiliate of
any Stockholder.

          9.  Descriptive Headings. The descriptive headings of the several
              --------------------
sections and paragraphs of this Agreement are inserted for reference only and
shall not limit or otherwise affect the meaning hereof.

          10. GOVERNING LAW. THIS AGREEMENT SHALL BE CONSTRUED AND ENFORCED IN
              -------------
ACCORDANCE WITH, AND THE RIGHTS OF THE PARTIES SHALL BE GOVERNED BY, THE LAWS OF
THE STATE OF DELAWARE WITHOUT REFERENCE TO THE PRINCIPLES OF CONFLICTS OF LAWS.

          11. Counterparts. This Agreement may be executed simultaneously in any
              ------------
number of counterparts, each of which shall be deemed an original, but all such
counterparts shall together constitute one and the same instrument.

          12. Entire Agreement. This Agreement embodies the entire agreement
              ----------------
and understanding between the Company and each other party hereto relating to
the subject matter hereof and supersedes all prior agreements and understandings
relating to such subject matter.

          13. Severability. If any provision of this Agreement, or the
              ------------
application of such provisions to any Person or circumstance, shall be held
invalid, the remainder of this Agreement, or the application of such provisions
to Persons or circumstances other than those to which it is held invalid, shall
not be affected thereby.

          14. Disposition of Shares. In the event of any public sales or
              ---------------------
distribution of the Registrable Securities effected pursuant to Section 2 of
this Agreement, the Stockholders shall use their reasonable best efforts to
effect, or cause to be effected, such public sale or distribution, so that,
without the prior written consent of the Company (which shall not be
unreasonably withheld), no participant or purchaser would Beneficially Own in
the aggregate 4% or more of all outstanding Common Stock of the Company. The
holders of Registrable Securities shall use their respective reasonable

                                      -23-

 
efforts in cooperation with the Company to effect as broad a disposition in any
such public sale or distribution as is reasonably practicable.

                                      -24-

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

                              MCKESSON CORPORATION
 
                              By: /s/ Nancy A. Miller
                                 _________________________________
                                   Name: Nancy A. Miller
                                   Title: Vice President and 
                                          Corporate Secretary

                              PREMIER PURCHASING PARTNERS, L.P.
                              By:  Premier Plans, Inc., its general partner

                              By: /s/ Robert W. O'Leary
                                 _________________________________
                                   Name: Robert W. O'Leary
                                   Title: CEO

                              WELSH, CARSON, ANDERSON & STOWE VII, L.P.
                              By:  WCAS VII Partners, L.P., its general partner

                              By: /s/ Russell Carson
                                 _________________________________
                                   Name: Russell Carson
                                   Title: General Partner

                              WCAS HEALTHCARE PARTNERS, L.P.
                              By:  WCAS HC Partners, its general partner

                              By: /s/ Russell Carson  
                                 _________________________________
                                   Name: Russell Carson
                                   Title: General Partner

                              /s/ Patrick J. Welsh
                              ____________________________________
                              Patrick J. Welsh

                              /s/ Russell L. Carson
                              ____________________________________
                              Russell L. Carson

                                      -25-

                              /s/ Bruce K. Anderson
                              _______________________________________
                              Bruce K. Anderson

                              DELAWARE CHARTER TRUST CO., as Trustee for the
                              Benefit of the IRA Rollover of Richard H. Stowe

                              /s/ Richard H. Stowe
                              _______________________________________
                              Richard H. Stowe

                              /s/ Andrew M. Paul
                              _______________________________________
                              Andrew M. Paul

                              /s/ Thomas E. McInerney
                              _______________________________________
                              Thomas E. McInerney

                              /s/ Laura VanBuren
                              _______________________________________
                              Laura VanBuren

                              /s/ James B. Hoover
                              _______________________________________
                              James B. Hoover

                              DELAWARE CHARTER TRUST CO., as Trustee for
                              the Benefit of the IRA Rollover of James B. Hoover

                              /s/  James B. Hoover
                              ______________________________________
                              James B. Hoover

                              /s/ Robert A. Minicucci
                              _______________________________________
                              Robert A. Minicucci

                              /s/ Anthony de Nicola
                              _______________________________________
                              Anthony de Nicola

                              /s/ Rudolph E. Rupert
                              _______________________________________
                              Rudolph E. Rupert

                              /s/ Paul B. Queally
                              _______________________________________
                              Paul B. Queally

                              /s/ Theodore H. Pacha
                              _______________________________________
                              Theodore H. Pacha

                                      -26-

 
                              /s/ David Nelson
                              _______________________________________
                              David Nelson

                              /s/ John Hamilton
                              _______________________________________
                              John Hamilton

                              /s/ John Rex-Waller
                              _______________________________________
                              John Rex-Waller

                              /s/ David Mawhinney
                              _______________________________________
                              David Mawhinney

                              /s/ Jeff Liesendahl
                              _______________________________________
                              Jeff Liesendahl

                              /s/ Michael Brennan
                              _______________________________________
                              Michael Brennan

                                      -27-