<PAGE>

                                                                   EXHIBIT 10.18

                                   AGREEMENT
                                   ---------

     This Agreement ("Agreement"), dated as of June 19, 2000, is between Express
Scripts, Inc., a Delaware corporation ("ESI"), and PlanetRx.com, Inc., a
Delaware corporation ("PlanetRx").

                                    RECITALS
                                    --------

     Whereas, ESI and PlanetRx entered into that certain Agreement dated as of
August 31, 1999 ("Previous Agreement").

     Whereas, ESI and PlanetRx mutually desire to terminate the Previous
Agreement and enter into this Agreement.

     In consideration of the agreements, covenants and conditions set forth
herein, intending to be legally bound, the parties hereto agree as follows:


Section 1.  Definitions.

     Whenever used in this Agreement with initial letters capitalized, the
following terms will have the following specified meanings:

     "Affiliate" means, with respect to a party, any Person that, directly or
indirectly, Controls, or is Controlled by, or is under common Control with, such
party; provided, however, that with respect to ESI, the term shall not include
       --------  -------
New York Life Insurance Company or its subsidiaries.

     "Change in Control of PlanetRx" means the following:

          (i) a Person becomes the "beneficial owner" (as defined in Rule 13d-3
     under the Securities Exchange Act of 1934, as amended), directly or
     indirectly, of securities of PlanetRx representing fifty percent (50%) or
     more of the combined voting power for the election of directors of
     PlanetRx's then outstanding securities;

          (ii) any consolidation, reorganization or merger of PlanetRx in which
     PlanetRx is not the continuing or surviving corporation or pursuant to
     which shares of common stock of PlanetRx would be converted into cash,
     securities or other property, other than a merger or reorganization of
     PlanetRx in which the holders of common stock immediately prior to the
     merger or reorganization have the same proportionate ownership of common
     stock of the surviving corporation immediately after the merger or
     reorganization;

          (iii) the shareholders of PlanetRx approve a plan of complete
     liquidation of PlanetRx; or

          (iv) the shareholders of PlanetRx approve an agreement for the sale or
     disposition by the Company of all or substantially all of the Company's
     assets or any transaction having a similar effect.

     "Confidential Information" means all trade secrets, know-how and nonpublic
information that relates to research, development, trade secrets, inventions,
source code, technical data, software programming, concepts, designs,
procedures, manufacturing, purchasing, accounting, engineering, marketing,
merchandising, selling, business plans or strategies and other proprietary or
confidential
<PAGE>

information, protectable under the laws of the United States or any other
nation, state or jurisdiction (including, but not limited to, any foreign
equivalents thereto).

     "Control" means the possession, directly or indirectly, of the power to
direct or cause the direction of the management and policies of a Person,
whether by contract or through the ownership of voting securities, including the
ownership of more than fifty percent (50%) of the equity, partnership or similar
interest in such Person.

     "Effective Date" means the date on which ESI receives the payment described
in Section 4 hereof.

     "ESI Member" means any individual who is entitled to benefits under a
prescription drug benefit plan provided by ESI, or a Person Controlled by ESI,
to an ESI Plan Sponsor or directly to such individual.

     "ESI Networks" means any or all of the networks of retail pharmacies
contracted with ESI to dispense prescription drugs to ESI Members. A pharmacy
network that is contracted by an ESI Plan Sponsor and merely administered by ESI
for such ESI Plan Sponsor shall not be deemed to be an ESI Network for purposes
of this Agreement.

     "ESI Plan Sponsor" means a sponsor of a health plan (such as an insurance
company, health maintenance organization, employer, Taft-Hartley plan, or other
Person, or a third party administrator acting on behalf of such a plan sponsor,
including a sponsor of a "cash and carry" or discounted card program) who
contracts with ESI or one of its Affiliates to provide a prescription drug
benefit to members of such health plan.

     "Equity Transaction" means, collectively, the transactions described in
that certain Asset Contribution and Reorganization Agreement dated as of August
31, 1999, among ESI, yourPharmacy.com, Inc., PlanetRx, PRX Holdings, Inc. and
PRX Acquisition Corp.

     "IP Right" means any copyright, trademark, patent, trade secret, moral
right or other intellectual property or proprietary right of any kind (including
applications therefor and, in the case of patents, any continuation or
divisional patent applications claiming priority thereto), whether arising under
the laws of the United States or any other nation, state or jurisdiction
(including any foreign equivalents thereto).

     "Internet" means the Internet or the World Wide Web (or any successor or
other online network including those using delivery over television, cable, set
top boxes, intranets, extranets and personal digital assistants).

     "Internet Pharmacy" means both Pure-Play Internet Pharmacies and Non-Pure-
Play Internet Pharmacies.

     "Non-Pure-Play Internet Pharmacy" means the Internet division or operations
owned and operated by pharmacy chains, traditional independent brick and mortar
pharmacies (having one or more physical locations), and other retail merchants
(such as supermarket chains and discount stores) that dispense prescription
drugs from a physical retail location and who, as an adjunct to their
traditional pharmacy operations also accept prescription orders via the Internet
and mail or deliver the Pharmaceutical Products to their customers.  As a matter
of clarification, a pharmacy that first had a brick and mortar location (even if
only one location) for retail pick-up, then adds the capability of accepting
prescription orders via the Internet as an adjunct to their traditional
operation, shall fall within this
<PAGE>

definition of Non-Pure-Play Internet Pharmacy. A Pure-Play Internet Pharmacy
that opens or acquires a material number of physical retail pharmacy locations
shall be considered a Non-Pure-Play Internet Pharmacy.

     "PBM Competitor" means a third party which engages in any of the following
activities, whether or not constituting such party's principal line of business:
contracting with health plan sponsors to provide (a) prescription drug benefits
via mail order, (b) point-of-sale electronic processing of pharmacy claims, (c)
formulary development and administration, or (d) for the development and/or
maintenance of retail pharmacy networks for fulfillment of consumer orders for
Pharmaceutical Products for members of a prescription drug benefit plan;
provided, that an insurance company, HMO or other Person whose principal
--------
business involves offering policies or plans of comprehensive health care and
which engages in such activities solely for the benefit of its policyholders or
members of its comprehensive health plans shall not be deemed to be a PBM
Competitor for purposes of this Agreement.

     "Person" means any individual, corporation, partnership, limited liability
company, trust, association or other entity or organization, including any
governmental or political subdivision or any agency or instrumentality thereof.

     "Pharmaceutical Products" means any product that under law may not be
dispensed except pursuant to a prescription order written by a licensed medical
professional and dispensed by a licensed pharmacy.

     "PlanetRx Site" means the website currently located at www.PlanetRx.com and
any successor site.

     "Pure-Play Internet Pharmacy" means a pharmacy which receives orders from
customers primarily through the Internet and is not a Non-Pure-Play Internet
Pharmacy.

Section 2.  Termination of Previous Agreement; Waiver.

     2.1  On the Effective Date, the Previous Agreement shall be deemed to be
terminated in its entirety, and the Internet Pharmacy Provider Agreement dated
as of August 31, 1999 by and between ESI and PlanetRx (the "Previous Internet
Pharmacy Agreement") shall be replaced in its entirety by the Amended and
Restated Internet Pharmacy Provider Agreement attached hereto as Exhibit I (the
                                                                 ---------
"New Internet Pharmacy Agreement"), which the parties shall execute and deliver
on such Effective Date.

     2.2  In exchange for the consideration set forth in this Agreement, ESI and
PlanetRx each hereby waives, releases and forever discharges the other of and
from any and all manner of action or actions, cause or causes of action, in law
or in equity, suits, debts, liens, contracts, agreements, promises, liability,
claims, demands, damages, loss, cost or expense, of any nature whatsoever, known
or unknown, fixed or contingent (hereinafter called "Claims"), which either now
has or may hereafter have against the other by reason of any matter, cause or
thing whatsoever from the beginning of time to the date hereof, including,
without limiting the generality of the foregoing, any Claims arising out of,
based upon or relating to the Previous Agreement.  These terms represent a full
and final settlement of any and all claims arising out of the Previous Agreement
and the Previous Internet Pharmacy Agreement, or arising out of any transaction
or relationship between ESI and PlanetRx of any kind whatsoever.

Section 3.  ESI Grant.

     3.1  Subject to the terms and conditions of this Agreement and the New
Internet Pharmacy
<PAGE>

Agreement, PlanetRx shall continue to be a participating pharmacy in the ESI
Networks for non-objecting ESI Plan Sponsors during the term hereof.

     3.2  Subject to the terms and conditions of this Agreement and the New
Internet Pharmacy Agreement, PlanetRx shall be the "Preferred" Internet Pharmacy
in the ESI Networks, except for such ESI Networks in which PlanetRx declines to
participate.  For purposes of the foregoing, "Preferred" shall mean that
PlanetRx shall be the recommended Internet Pharmacy vendor to ESI Plan Sponsors
(although no level of promotion of PlanetRx is guaranteed by ESI).
Notwithstanding the foregoing:  (i) ESI may permit Non-Pure-Play Internet
Pharmacies into ESI Networks, and list such Non-Pure-Play Internet Pharmacies as
participants in the applicable ESI Networks; (ii) ESI may recommend specific
Non-Pure-Play Internet Pharmacies to ESI Plan Sponsors if and only if the
applicable ESI Plan Sponsor seeks an alternative Internet Pharmacy (i.e.,
alternative to PlanetRx); (iii) ESI may permit other Pure-Play Internet
Pharmacies into applicable ESI Networks if and then only for a specific ESI Plan
Sponsor that requests that such specific Pure-Play Internet Pharmacy participate
in its applicable ESI Network, and (iv) ESI may honor contractual obligations of
a business or entity acquired by ESI under agreements with third parties
existing at the time of such acquisition until such agreements can be lawfully
terminated without financial or other penalty.

     3.3  In the event of (i) a Change in Control of PlanetRx, or (ii) the
acquisition of 30% or more of PlanetRx's voting stock by a PBM Competitor,
PlanetRx shall notify ESI in writing of the occurrence (or proposed occurrence)
thereof and ESI shall have the right, within 30 days of receipt of such notice,
to terminate Section 3.2 hereof by giving PlanetRx written notice of said
termination.  In such case, said termination shall be effective 30 days after
receipt of notice thereof by PlanetRx.

Section 4.  Payment.

     PlanetRx shall pay ESI eight million dollars ($8,000,000) on July 5, 2000,
by wire transfer in immediately available funds, as PlanetRx's payment in full
of all obligations under this Agreement and the Previous Agreement (i.e., said
payment includes the Operating Fee payable to ESI under the Previous Agreement
for the period April 1 to June 30, 2000).

Section 5.  PlanetRx Stock; Restrictions.

     ESI shall retain the shares of PlanetRx Common Stock received under the
Equity Transaction agreement.  ESI agrees that prior to January 1, 2001, ESI
shall not, without the prior written consent of PlanetRx, directly or
indirectly, offer, sell, offer to sell, contract to sell, pledge, grant any
option to purchase or otherwise dispose of or transfer (or announce any offer,
sale, offer of sale, contract of sale, pledge, grant of any option to purchase
or other disposition or transfer) any such shares of PlanetRx Common Stock or
any securities into which such shares may be converted or exchanged; provided,
however, that ESI may transfer such shares or securities in a private
transaction in accordance with an exemption from registration under applicable
securities laws if, prior to such transfer, the transferee agrees in writing
with PlanetRx to be bound by the restrictions set forth in this Section 5 with
respect to such shares.

Section 6.  Technology Deposit.

     The parties hereto shall negotiate in good faith and use their best efforts
to execute and deliver, on or before July 31, 2000, a mutually acceptable
Depository Agreement, which shall require PlanetRx to promptly deposit the
source code for and a working copy of the then current versions of all software
developed by PlanetRx that is incorporated into the PlanetRx Site in accordance
with the terms of said Depository Agreement.  Such Depository Agreement shall
grant ESI a non-exclusive, non-transferable, non-sublicensable, irrevocable,
worldwide, royalty free, fully paid up license to any PlanetRx IP Rights
<PAGE>

relating to such software solely for ESI's use for its own website, provided ESI
shall agree not to use said license unless and until PlanetRx (i) ceases to do
business or otherwise terminates its operation on the PlanetRx Site, (ii) files
for or converts to a case for relief under Chapter 7 of the United States
Bankruptcy Code ("Bankruptcy Code") or a liquidating plan has been confirmed and
gone effective in a case under Chapter 11 of the Bankruptcy Code in which
PlanetRx is the debtor and such plan provides for the liquidation of the
business of PlanetRx, or (iii) liquidates, dissolves or otherwise winds-up its
affairs.  The source code and working copy of the software shall be delivered to
ESI by the depository agent immediately upon the occurrence of any of the
foregoing events.  In addition, the Depository Agreement shall not require any
future performance on the part of PlanetRx (other than the delivery of the
source code and working copy of the software at the outset).

Section 7.  Nondisclosure.

      7.1  A party (the "Receiving party") receiving any Confidential
Information of the other party (the "Disclosing party") will exercise a
reasonable degree of care, but in no event less than the same degree of care
that it uses to protect its own confidential information of a like nature, to
keep confidential and not disclose such Confidential Information and not to use
such Confidential Information except as authorized by this Agreement. Without
limiting the generality of the foregoing, the Receiving Party shall disclose the
Confidential Information of the other party only to those of its employees and
contractors (a) who have a need to know the Confidential Information in order to
exercise its license to such Confidential Information, and (b) who are
contractually bound to terms and conditions protecting against the unauthorized
disclosure or use of Confidential Information.

     7.2  The obligations set forth in Section 7.1 above shall not apply to any
Confidential Information to the extent it: (a) is approved by prior written
authorization of the Disclosing party for release by the Receiving party; (b) is
disclosed in order to comply with a judicial order issued by a court of
competent jurisdiction, in which event the Receiving party shall give prior
written notice to the Disclosing party of such disclosure as soon as practicable
and shall cooperate with the Disclosing party in using all reasonable efforts to
obtain an appropriate protective order or equivalent, provided that the
information shall continue to be Confidential Information to the extent it is
covered by such protective order or equivalent; (c) becomes generally available
to the public through any means other than a breach by the Receiving party of
its obligations under this Agreement; (d) was in the possession of the Receiving
party without obligation of confidentiality prior to receipt or disclosure under
this Agreement as evidenced by written records made prior to such receipt or
disclosure; (e) is developed independently by the Receiving party without the
use of or benefit from any of the Confidential Information of the other party or
without breach of this Agreement, as evidenced by records of the Receiving
party; or (f) is required to be disclosed by any national securities exchange,
by government rule or regulation (e.g., in connection with a securities filing)
or by any other provisions of applicable law, provided that the Receiving party
gives the Disclosing party advance written notice (to the extent practicable) of
the disclosure and cooperates with the Disclosing party in any reasonable
attempt to limit the scope of the required disclosure.  In any dispute over
whether information is Confidential Information under this Agreement, it will be
the burden of the Receiving party to show that such contested information falls
within the exceptions set forth in this Section 7.

Section 8.  Representations and Warranties

     8.1  Representations and Warranties of PlanetRx.  PlanetRx hereby
          -------------------------------------------
represents and warrants to ESI:

               (a) Authorization. All corporate action on the part of PlanetRx,
                   -------------
          its officers, directors and stockholders necessary for the
          authorization, execution and delivery of this Agreement by and
<PAGE>

          between PlanetRx and ESI, and the performance of all obligations of
          PlanetRx hereunder has been taken, and this Agreement, when executed
          and delivered by PlanetRx, will constitute valid and legally binding
          obligations of PlanetRx, enforceable against PlanetRx in accordance
          with its terms except as limited by applicable bankruptcy, insolvency,
          reorganization, moratorium, fraudulent conveyance, and other laws of
          general application affecting enforcement of creditors' rights
          generally, as limited by laws relating to the availability of specific
          performance, injunctive relief, or other equitable remedies.

               (b) Compliance with Other Instruments. The execution, delivery
                   ---------------------------------
          and performance of this Agreement and the consummation of the
          transactions contemplated hereby will not result in any violation of
          or be in conflict with or constitute, with or without the passage of
          time and giving of notice, a default under any provision of PlanetRx's
          or any of its subsidiaries' charter or bylaws or any instrument,
          judgment, order, writ, decree or contract to which PlanetRx or any of
          its subsidiaries is a party or by which PlanetRx or any of its
          subsidiaries is bound, or any provision of any federal or state
          statute, rule or regulation applicable to PlanetRx or any of its
          subsidiaries, the effect of which would have a material adverse effect
          on the ability of PlanetRx or any of its subsidiaries to perform its
          obligations under this Agreement or result in the creation of any
          lien, charge or encumbrance upon any assets of PlanetRx or any of its
          subsidiaries.


     8.2  Representations and Warranties of ESI.  ESI hereby represents and
          -------------------------------------
warrants to PlanetRx:

               (a) Authorization. All corporate action on the part of ESI, its
                   -------------
          officers, directors and stockholders necessary for the authorization,
          execution and delivery of this Agreement, and the performance of all
          obligations of ESI hereunder has been taken, and this Agreement, when
          executed and delivered by ESI, will constitute valid and legally
          binding obligations of ESI, enforceable against ESI in accordance with
          its terms except as limited by applicable bankruptcy, insolvency,
          reorganization, moratorium, fraudulent conveyance, and other laws of
          general application affecting enforcement of creditors' rights
          generally, as limited by laws relating to the availability of specific
          performance, injunctive relief, or other equitable remedies.

               (b) Compliance with Other Instruments. The execution, delivery
                   ---------------------------------
          and performance of this Agreement and the consummation of the
          transactions contemplated hereby will not result in any violation of
          or be in conflict with or constitute, with or without the passage of
          time and giving of notice, a default under any provision of ESI's or
          any of its subsidiaries' charter or bylaws or any instrument,
          judgment, order, writ, decree or contract to which ESI or any of its
          subsidiaries is a party or by which ESI or any of its subsidiaries is
          bound, or any provision of any federal or state statute, rule or
          regulation applicable to ESI or any of its subsidiaries, the effect of
          which would have a material adverse effect on the ability of ESI or
          any of its subsidiaries to perform its obligations under this
          Agreement or result in the creation of any lien, charge or encumbrance
          upon any assets of ESI or any of its subsidiaries.

Section 9.  Outsourcing Agreement

     The parties will engage in discussions regarding entering into an
outsourcing agreement pursuant to which PlanetRx would be permitted to fill mail
pharmacy prescriptions for ESI, at ESI's sole discretion.
<PAGE>

Section 10.  Effectiveness and Term; Termination; Survival

     10.1  Effectiveness and Term.  This Agreement shall become effective on the
           ----------------------
Effective Date and the term hereof shall continue for a period of 5 years from
such Effective Date, unless terminated earlier in accordance with the terms
hereof; provided, however, that if the Effective Date does not occur on or
        --------  -------
before July 6, 2000, (i) this Agreement shall be deemed to be null and void and
of no force and effect, and ESI shall have all its rights and remedies under the
Previous Agreement, and (ii) nothing contained in this Agreement shall be
considered prejudicial to ESI with respect to its rights or remedies under the
Previous Agreement or otherwise compromise any of such rights or remedies.

     10.2  Termination.  The following shall be events of default under this
           -----------
Agreement, and shall give ESI the right to immediately terminate this Agreement:

                 (a) If PlanetRx is in material breach of any of its obligations
           under this Agreement or the Equity Transaction agreements (including
           any material breach or inaccuracy of its representations or
           warranties that has a material adverse effect on the ability of
           PlanetRx to perform its obligations under this Agreement or the
           Equity Transaction agreements), which breach PlanetRx does not cure
           within sixty (60) days after ESI gives PlanetRx written notice
           thereof;

                 (b) PlanetRx engages in prescribing medicine or referring
           consumers to physicians or other medical or dental professionals to
           obtain prescriptions for Pharmaceutical Products;

                 (c) PlanetRx fails to maintain its privacy structure in
           accordance with state and federal regulatory requirements and
           industry standards, as may be reflected in certification standards of
           organizations such as Trust e, BBB, VIPPS, the NABP or similar
           organizations and at a level comparable to that maintained by other
           Internet Pharmacies.

     10.3  Survival.  Sections 2.2 and 7 shall survive the termination of this
           --------
Agreement. Section 6 shall survive termination of this Agreement due to
PlanetRx's breach if the Depository Agreement is not executed and delivered
prior to said termination.

Section 11.  General.

     11.1  Relationship.  The parties are independent contractors under this
           ------------
Agreement.  Each party acknowledges and agrees that it is not and will not be
during the term an employee or an agent of the other party.  Nothing in this
Agreement will be deemed to constitute, create, give effect to or otherwise
recognize a joint venture, partnership, franchise or business entity of any
kind.

     11.2  Assignment.  This Agreement shall be binding upon and inure to the
           ----------
benefit of the parties hereto, and the legal representatives, successors in
interest and permitted assigns, respectively, of each such party.  This
Agreement shall not be assigned in whole or in part by any party without the
prior written consent of the other party, such consent not to be unreasonably
withheld except to an entity that acquires all or substantially all of the
business or assets of such party, subject to Section 3.3.
<PAGE>

     11.3  Change in Existing Law.  In the event that there is a change in law
           ----------------------
or regulation, a change in interpretation of existing law or regulation, or new
enforcement of existing law or regulation such that any provision of this
Agreement shall be deemed illegal, invalid or unenforceable, or impractical, the
parties shall in good faith renegotiate such affected terms so as to put the
parties in as close to the same economic position as they would have been in had
the affected provisions not been deemed illegal, invalid or unenforceable.

     11.4  Notices.  All notices, requests, demands, applications, services of
           -------
process, and other communications that are required to be or may be given under
this Agreement shall be in writing and shall be deemed to have been duly given
if sent by telecopy or facsimile transmission, answer back requested, or
delivered by courier or mailed, certified first class mail, postage prepaid,
return receipt requested, to the parties to this Agreement at the following
addresses:

     If to ESI:  Express Scripts, Inc.
                 13900 Riverport Drive
                 Maryland Heights, Missouri  63043
                 Attention: President
                 Fax:  314-770-1581

     With a copy to:  Express Scripts, Inc.
                      13900 Riverport Drive
                      Maryland Heights, Missouri  63043
                      Attention: General Counsel
                      Fax:  314-702-7120

     If to PlanetRx:  PlanetRx.com, Inc.
                      349 Oyster Point Blvd., Suite 201
                      South San Francisco, California, 94080
                      Attention:  General Counsel
                      Fax:  650-616-1585

or to such other address as the party shall have furnished to the other party by
notice given in accordance with this Section 11.4.  Such notice shall be
effective (i) if delivered in person or by courier, upon actual receipt by the
intended recipient, or (ii) if sent by telecopy or facsimile transmission, on
the date of transmission unless transmitted after normal business hours, in
which case on the following date, or (iii) if mailed, upon the date of first
attempted delivery.

     11.5  Waiver.  No provision of this Agreement shall be deemed to be waived
           ------
and no breach excused unless such waiver or consent shall be in writing and
signed by the party that is claimed to have waived or consented.  The failure of
a party at any time, or from time to time, to require performance by the other
party of any provision hereof shall in no way affect the rights of such party
thereafter to enforce the same nor shall the waiver by a party of any breach of
any provision hereof by the other party constitute a waiver of any succeeding
breach of such provision, or a waiver of any provision itself, or a waiver of
any other provisions hereof.

     11.6  Severability.  This Agreement will be enforced to the fullest extent
           ------------
permitted by applicable law.  If for any reason any provision of this Agreement
is held to be invalid or unenforceable to any extent, then: (a) such provision
will be interpreted, construed or reformed to the extent reasonably required to
render the same valid, enforceable and consistent with the original intent
underlying such provision; (b) such provision will be void to the extent it is
held to be invalid or unenforceable; (c) such provision will remain in effect to
the extent that it is not invalid or unenforceable; and (d) such invalidity or
unenforceability will not affect any other provision of this Agreement or any
other agreement between the parties.
<PAGE>

     11.7  Remedies.  Except as otherwise expressly provided in this Agreement,
           --------
each and all of the rights and remedies provided in this Agreement, and each and
all of the remedies allowed at law and in equity, will be cumulative, and the
exercise of one right or remedy will not be exclusive of the right to exercise
or resort to any and all other rights or remedies provided in this Agreement or
at law or in equity.

     11.8  Injunctive Relief.  The parties acknowledge that a material breach of
           -----------------
Section 7 of this Agreement would cause irreparable harm, the extent of which
would be difficult to ascertain. Accordingly, they agree that, in addition to
any other legal remedies to which the non-breaching party may be entitled, such
party will be entitled to obtain immediate injunctive relief in the event of a
material breach of this Agreement.

     11.9  Governing Law.  This Agreement will be governed by and construed
           -------------
according to the laws of the State of Delaware without regard to its choice of
law provisions.  The parties consent to the jurisdiction of such courts and
waive any right to assert that any such court constitutes an inconvenient or
improper forum.

     11.10  Publicity.  Neither party shall, without the approval of the other,
            ---------
make any press release or other public announcement concerning the transactions
contemplated by the Agreements, except as and to the extent that any such party
shall be so obligated by law or by the rules, regulations or policies of any
national securities exchange or association or governmental entity, in which
case the other party shall be advised and the parties shall use reasonable
efforts to cause a mutually agreeable release or announcement to be issued;
provided, however, that the parties hereby acknowledge and agree that
communications among employees of the parties and their attorneys,
representatives and agents necessary to consummate the transactions contemplated
hereby shall not be deemed a public announcement for purposes of this Section
11.10.  Upon the execution and delivery of this Agreement, the parties hereto
will cooperate in respect of the immediate issuance of a mutually acceptable
press release relating to the transactions contemplated by the Agreements.

     11.11  Entire Agreement.  All Exhibits to this Agreement are incorporated
            ----------------
in and constitute a part of this Agreement.  This Agreement, including the
Exhibits and Schedules hereto, each as amended from time to time, constitute the
entire understanding between the parties in relation to the subject matter
hereof and supersede all prior discussions, agreements and representations
related to this subject matter, whether oral or written and whether or not
executed by a party.  Unless otherwise provided in this Agreement, no
modification, amendment or other change may be made to this Agreement or any
part thereof unless reduced to writing and executed by authorized
representatives of all parties.

     11.12  Counterparts.  This Agreement may be executed in two or more
            ------------
counterparts, each of which will be deemed an original, but all of which
together will constitute one and the same instrument.

     11.13  Titles and Subtitles.  The titles and subtitles used in this
            --------------------
Agreement and in the Exhibits and Schedules hereto are used for convenience only
and are not to be considered in construing or interpreting this Agreement.

     11.14  Force Majeure.  Neither party shall be responsible for a failure to
            -------------
meet its obligations under this Agreement to the extent caused by the following:
(i) materially inaccurate data submitted by the other party; (ii) any failure of
equipment, facilities or services not controlled or supplied by such party; or
(iii) failure(s) caused by acts of God, acts of nature, riots and other major
civil disturbances, strike by such party's personnel, sabotage, injunctions or
applicable laws or regulations, in each case without breach by such party of any
obligations under this Agreement with regard to either such event or such
failure.  ESI or PlanetRx, as applicable, agrees to use its commercially
reasonable efforts to restore performance of its obligations under this
Agreement as soon as reasonably practicable following any such event.

                  (Remainder of Page Intentionally Left Blank)
<PAGE>

(Signature Page of Agreement dated as of June 19, 2000, between Express Scripts,
                         Inc., and PlanetRx.com, Inc.,)

     IN WITNESS WHEREOF, the parties have duly entered into this Agreement as of
the date first written above.

ESI:                                         PlanetRx:


EXPRESS SCRIPTS, INC.                        PLANETRX.COM, INC.


By: /s/ George Paz                           By: /s/ Michael Beindorff

Name: George Paz                             Name: Michael Beindorff

Title: Senior Vice President                 Title: Chief Executive Officer
and Chief Financial Officer
<PAGE>

                                   Exhibit I
                                   ---------

                           FORM OF INTERNET PHARMACY
                           -------------------------
                               PROVIDER AGREEMENT
                               ------------------

     THIS INTERNET PHARMACY PROVIDER AGREEMENT ("Agreement") is effective as of
this 5th day of July, 2000 (the "Effective Date"), by and between Express
Scripts, Inc., a Delaware corporation ("ESI"), and  PlanetRx.com, Inc. a
Delaware corporation ("Provider").

                                    RECITALS

     A.  ESI provides and manages prescription drug programs for its clients,
     which programs include claims administration, mail service dispensing and
     other pharmacy benefit management services.

     B.  Provider, a Web-based pharmacy, wishes to provide Internet Pharmacy
     services to eligible members of certain prescription drug programs by
     participating in one or more of ESI's pharmacy networks, all in accordance
     with and subject to the terms and conditions set forth herein.

                              TERMS AND CONDITIONS

1. DEFINITIONS   For purposes of this Agreement, the following capitalized
   -----------
     terms shall have the meanings set forth below:

     "Average Wholesale Price" or "AWP" means the average wholesale price of a
     prescription drug based upon the most current information provided to ESI
     by drug pricing services such as First Databank, Redbook or other source
     generally recognized in the retail prescription drug industry selected by
     ESI.

     "Benefit Plan" means a health care plan pursuant to which prescription drug
     benefits are available to Members.

     "Copayment" means that portion of the total charge for each prescription
     drug that a Member is required to pay to Provider in accordance with that
     Member's Prescription Drug Program and the provisions of Section 2.A
     hereof, whether designated as a "copayment" or "deductible" under the
     applicable Prescription Drug Program.

     "Covered  Medications" means those prescription drugs, supplies and other
     items prescribed by an authorized, licensed medical practitioner that are
     covered by a Benefit Plan.

     "DAW Code" means the "dispense as written" codes as developed by the NCPDP,
     as may be revised from time to time.

     "Formulary" means a list of preferred drugs developed by ESI or a Sponsor
     and revised periodically, which drugs physicians are encouraged to
     prescribe and pharmacists are encouraged to dispense, consistent with their
     professional judgment and applicable medical and pharmaceutical laws and
     procedures, and which Members are encouraged to use.  ESI will send
     Formulary information to the Provider on-line at time of claim
     adjudication, or in such other manner as ESI deems appropriate.
<PAGE>

     "Internet Pharmacy" means a pharmacy which does not have a physical
     location for patrons to visit for retail sales but that receives orders
     from customers only through the Internet, but does not include the Internet
     division or operations of pharmacy chains and other retail merchants (such
     as supermarket chains and discount stores) that dispense prescription drugs
     and who, as an adjunct to their traditional pharmacy operations also accept
     prescription orders via the Internet and mail or deliver the Pharmaceutical
     Products to their customers.

     "MAC" means the maximum allowable cost that ESI will pay Provider for
     generic drugs and multi-source brand drugs where a generic drug is
     available (except in cases where the prescriber or Member insist upon
     receiving the multi-source brand drug.  MAC is determined by ESI, in its
     sole discretion, based on industry wholesale trends and related current
     pricing data for generic drugs.

     "Internet" means the Internet or the World Wide Web (or any successor or
     other online network including those using delivery over television, cable,
     set top boxes, intranets, extranets and personal digital assistants).

     "Member" means a subscriber and his or her eligible dependents to whom
     benefits are available pursuant to a Prescription Drug Program.

     "NCPDP" means the National Council for Prescription Drug Programs, or any
     successor organization.

     "Operating Agreement" means the Agreement entered into by Provider and ESI,
     dated as of June 19, 2000.

     "Prescription Drug Program" means prescription drug program services
     provided to a Sponsor pursuant to an agreement with ESI, including any
     Formulary.

     "Provider Manual" is a written description of ESI's generally applicable
     practices, policies, rules and procedures provided by ESI for pharmacies
     dispensing Covered Medications to Members, including such provisions as are
     specific to Internet Pharmacies.  The Provider Manual may be revised from
     time to time by ESI in its sole discretion.

     "Sponsor" means any health maintenance organization (HMO), insurance
     company, employer or other organization having principal financial
     responsibility for payment of Covered Medications provided to Members under
     a Prescription Drug Program, or a person or entity (such as a third party
     administrator) contracting on behalf of such an entity, or a person or
     entity sponsoring a "cash and carry" or discounted card program.

     "Usual and Customary Retail Price" means the Provider's usual and customary
     retail price of a Covered Medication in a cash transaction (in the quantity
     dispensed) on the date that it is dispensed, including any discounts or
     special promotions offered on such date.
<PAGE>

2.   PHARMACY SERVICES
     -----------------

     A.   Provider shall provide Internet Pharmacy services to Members through
          its Internet Pharmacy website in connection with ESI's Prescription
          Drug Programs, and agrees to perform the following:

          1. Verification of Eligibility. Verify on-line with ESI that the
             ---------------------------
             Member submitting the prescription request is eligible for benefits
             under the Prescription Drug Program.  Provider shall require the
             Member provide a health plan identification number.

          2. Dispensing.  Dispense Covered Medications to each Member (not to
             ----------
             exceed a one month's supply) in accordance with all applicable laws
             and regulations and the applicable Prescription Drug Program.  Any
             prescription for a Member for a Covered Medication greater than
             one-month's supply shall be transferred to ESI for fulfillment
             unless otherwise mutually agreed to by the parties.  The parties
             will develop procedures for the transfer of such prescription
             orders to ESI.  Initially, however, Provider will create an order
             for each Member request for such a prescription; obtain approval
             from the credit card issuer for the amount of the Copayment; and
             remit the Copayment to ESI when received, net of the credit card
             issuer's fee.

          3. Claims Processing.  Submit each and every prescription drug claim
             -----------------
             for a Member to ESI in a current and industry accepted NCPDP
             telecommunications format for processing and payment in accordance
             with the requirements set forth in the Provider Manual, which
             submission shall include, among other things, (a) the DAW Code, (b)
             the nationally determined unique provider identifier, when such
             identifier is readily available (or the DEA number) or such other
             identifier agreed to by ESI for the prescribing medical
             practitioner, and (c) the NDC number for the original package size
             from which the Covered Medication was dispensed. If a claim cannot
             be transmitted on-line, Provider will make reasonable attempts to
             retransmit the claim. In no event shall a claim be submitted later
             than 30 days after the prescription is filled. All messages and DUR
             information transmitted by ESI for paid or rejected claims will be
             displayed for the dispensing pharmacist at the time of claim
             processing. Provider will respond to on-line messages received from
             ESI.

          4. Copayments.  Charge Members and collect the applicable Copayment
             -----------
             indicated on-line or if on-line processing is unavailable, then as
             outlined in the Provider Manual, subject to the provisions of
             Section 2.B. hereof regarding coupons.  Copayments for Members may
             not be waived or discounted without ESI's consent, nor may Provider
             accept coupons issued by any person other than ESI in lieu of
             collecting the Copayment in cash (including charge or debit cards)
             for Members submitting prescriptions for Covered Medications.  In
             no event (including but not limited to nonpayment by ESI or ESI's
             insolvency) shall Provider bill, charge, collect a deposit from, or
             seek any other fees, taxes or surcharges or any other compensation
             from any Member for any Covered Medications or services provided in
             connection herewith other than (i) the applicable Copayment (and in
             no event shall ESI be liable for any Copayment), and (ii) standard
             shipping charges, which shall not be less favorable than the
             charges to Provider customers that are not Members.  This Section
             2.A.4 shall survive termination of this Agreement, regardless of
             the cause of termination, and shall be construed for the benefit of
             Members.
<PAGE>

          5. Verification of Dispensing.  Maintain order detail and method of
             --------------------------
             shipment records (or other evidence specifically approved by ESI)
             for each Covered Medication dispensed to Members.

          6. Consultation Services.  Provide reasonable consultation services
             ---------------------
             with regard to Covered Medications that the Member is taking.
             Reasonable consultation services shall include, at a minimum, such
             consultation as is required under applicable federal or state law
             or regulation.

     B.   Standards of Service.  Provider shall perform the services required of
          --------------------
          it under this Agreement with at least the same standard of care, skill
          and diligence that is customarily used by pharmacies, including VIPPS
          certified internet pharmacies, in the community and that Provider uses
          in serving other customers.   Provider shall not engage in prescribing
          prescription drugs or in referring Members to physicians or other
          medical or dental professionals for prescriptions for Covered
          Medications.  Provider agrees that the administrative and billing
          practices applied and the prices charged for products and services
          that are not Covered Medications provided to Members shall be no less
          favorable than such practices applied or such prices charged to other
          customers.  Provider shall not refuse to provide services required
          under a Benefit Plan or attempt to disenroll any Member.  Further,
          Provider agrees to implement and maintain a tracking program for
          orders identified by Members as lost in the mail.  Provider will
          comply with the Pharmacy Practice Standards promulgated from time to
          time by the Pharmaceutical Care Management Association (PCMA), whether
          or not Provider is a member of such association, or, if such
          association ceases to promulgate such standards, the comparable
          standards of any generally recognized successor organization that
          promulgates standards for mail and/or Internet pharmacies.

     C.   Compliance with Applicable Law; Permits and Licenses.  Provider shall
          ----------------------------------------------------
          be bound by and comply with the provisions of all applicable laws,
          rules and regulations of the state board of pharmacy and other
          governmental bodies having jurisdiction over Provider, including non-
          resident pharmacy requirements.  Where required by a Sponsor that is a
          health maintenance organization, this Agreement shall be subject to
          the Federal Health Maintenance Organization Act, 42 U.S.C. 300 et.
          seq., or any successor statutes and the rules and regulations
          thereunder, and to the comparable laws and regulations of any
          applicable state, which laws, rules and regulations shall take
          precedence over this Agreement to the extent of any inconsistency.
          Provider shall maintain at all times all required federal, state and
          local licenses, non-resident pharmacy registrations and licenses,
          certificates and permits that are necessary to allow Provider to
          dispense Covered Medications to Members.  Provider shall notify ESI in
          writing immediately in the event of any suspension, revocation,
          restriction or limitation on any such license, registration,
          certificate or permit.

     D.   Drug Utilization Review; Compliance with Formularies and Provider
          -----------------------------------------------------------------
          Manual.  Provider shall (1) cooperate with ESI's procedures for drug
          ------
          utilization review and generic substitution, as set forth from time to
          time in the Provider Manual; (2) comply with ESI's procedures for
          calling prescribers to facilitate generic substitution and Formulary
          compliance, and other programs established by a Sponsor; and (3)
          comply with the Provider Manual.  Provider shall use commercially
          reasonable efforts to comply with the applicable Formulary when
          dispensing Covered Medications to Members.  Without limiting the
          generality of the foregoing, in no event will Provider (i) attempt to
          switch a
<PAGE>

          Member's prescription to a drug that is not a Formulary drug on the
          applicable Formulary, except for generic substitution opportunities or
          where required by medical necessity. Provider agrees that ESI's
          manufacturer agreements, therapeutic programs and formularies take
          precedence with the manufacturers over any such agreements or programs
          to which Provider is a party with respect to Covered Medications
          dispensed to Members. Provider will not implement any substitution
          program for Members of Prescription Drug Programs that is inconsistent
          with such Prescription Drug Program, including the applicable
          Formulary.

     E.   Hours of Service.   Provider shall operate and be available to Members
          ----------------
          on-line 24 hours a day, 7 days a week.

     F.   Member Communications.  All outbound communications from Provider to
          ---------------------
          ESI Members (identifiable as such by Provider) (other than those
          customarily occurring between a pharmacist and a patient with respect
          to the dispensing of Pharmaceutical Products or those reasonably
          necessary to fulfill a Member's order) shall require ESI's prior
          written approval, provided, however, that in the event that Provider
          shall request consent for a specific promotion, ESI shall provide a
          response to such request within one (1) business day.

3.  PROVIDER COMPENSATION
    ---------------------

     A.   Reimbursement Pricing -- 30-Day Prescriptions.  In addition to any
          ----------------------------------------------
          Copayments, Provider shall receive payments from ESI for pharmacy
          services described in Section 2 hereof, for prescriptions for
          medication for a 30-day supply of medication or less, in accordance
          with the payment schedule set forth in the applicable Exhibit A, or in
                                                                ---------
          any special pricing rider for a specific ESI network to which Provider
          may agree (less the applicable Copayments).  Payments shall be based
          upon the prescription drug claims submitted to ESI pursuant to Section
          2.A.3 hereof.  The parties agree to negotiate in good faith
          adjustments to the transfer pricing/reimbursement fees for a
          particular network if, during the term, ESI recontracts one or more of
          its retail pharmacy networks (e.g., PerxCare, PerxSelect or any
          successors thereto), as necessary to maintain the positive rate
          differential between Provider and the retail network pharmacies.

     B.   Payment Schedule for Reimbursement Pricing.  ESI shall pay Provider
          ------------------------------------------
          for approved claims for pharmacy services prescribed in Section 2
          hereof for prescriptions for medication for a 30-day supply of
          medication or less, on a twice monthly payment cycle; approved claims
          will be paid on average of thirty (30) days from date of acceptance.
          Rejected or disputed claims must be resubmitted within 30 days of the
          initial rejection.  ESI may deny payment for any claim not submitted
          within these time periods.  Further, Provider and ESI hereby agree
          that ESI may refuse to pay any claim not submitted in accordance with
          the provisions of this Section 3.A. and of Section 2.A.3 hereof.
          Except with respect to Copayments, Provider shall look solely to ESI
          for compensation for Covered Medications and other services provided
          to Members pursuant to this Agreement.  ESI will not reverse any of
          its approvals for properly submitted claims with respect to which
          Provider has complied with the terms of this Agreement.

     C.   Fulfillment Pricing.  For prescriptions ordered by a Member through
          --------------------
          Provider but fulfilled/dispensed by ESI ("Fulfillment Claims"),
          Provider shall receive payments from ESI equal to ESI's drug
          ingredient cost upon ESI's collection of payment from the
<PAGE>

          applicable Sponsor. Provider shall bear the risk of loss for the
          inability of ESI to collect from the Sponsor. If ESI is unable to
          collect from the Sponsor, ESI will assign its rights in such
          receivable to Provider. Provider will remit the Copayments on all
          Fulfillment Claims to ESI, net of any credit card issuer's fee on the
          transaction.

     D.   Payment Schedule for Fulfillment Pricing.  ESI shall pay Provider for
          ----------------------------------------
          Fulfillment Claims based on a schedule mutually agreeable to the
          parties.

     E.   Order Fees.  ESI shall pay Provider an order processing fee for
          ----------
          Fulfillment Claims of [*] per prescription, payable monthly.

     F.   Preferred Product Fees.  ESI shall pay Provider a preferred product
          ----------------------
          fee of [*] per prescription for each attempt to convert a prescription
          for a non-preferred product to a preferred product for prescriptions
          filled by Provider.  The method of communication to the Member or the
          prescriber shall be at the discretion of Provider.

     G.   Remittance Advices.  Provider agrees that it is obligated to review
          ------------------
          remittance advices to verify their accuracy, and must notify ESI in
          writing within 45 days of receipt of each such remittance advice of
          any disputed information thereon.  Upon proper notice to ESI and
          verification of amounts to be paid, if any, ESI shall only be
          responsible for remitting additional payments to a Provider in
          connection with the specific disputed remittance advice.  If Provider
          does not notify ESI in the manner and time provided herein, ESI shall
          have no further responsibility with respect to such remittance.

     H.   Taxes:  Transmission Charges.  With respect to Covered Medications
          ----------------------------
          dispensed to Members by Provider, if permitted by the terms of its
          contract with the Sponsor, ESI will bill the Sponsor for any Federal,
          state, or local sales taxes payable with respect to any sales of
          Covered Medications to a Member, and will remit to Provider any such
          taxes collected from Sponsors.  Provider shall remit any such sales
          taxes to the other taxes or surcharges associated with its performance
          under this Agreement (but not for income taxes payable on ESI's
          income).  For purposes of this section "sales tax" means any excise
          tax on Covered Medications now or hereafter in existence required to
          be collected or paid by a retail seller on consumer retail sales,
          whether designed as a sales tax, gross receipts tax, retail occupation
          tax, value added tax, or otherwise.  Provider shall be solely
          responsible for expenses included in transmitting claims to ESI.  If
          Provider transfers a prescription order to ESI for fulfillment, ESI
          shall be solely responsible for any applicable sales taxes and any
          other taxes or surcharges associated with fulfilling such prescription
          order (but not for income taxes payable on Provider's income).

4.   COMPENSATION TO ESI. For prescriptions ordered by a Member through Provider
     -------------------
     but fulfilled/dispensed by ESI because the quantity dispensed exceeded a 30
     days supply, Provider shall reimburse ESI for its drug ingredient cost and
     remit the applicable Copayment to ESI. Provider shall be responsible for
     collecting the Copayment from the Member.  Provider shall make such
     payments to ESI based on a schedule mutually agreeable to the parties.


-------------------
*  Confidential treatment has been requested for certain portions which have
been blacked out in the copy of the exhibit filed with the Securities and
Exchange Commission. The omitted information has been filed separately with the
Securities and Exchange Commission pursuant to the application for confidential
treatment.
<PAGE>

5.   LIABILITY INSURANCE; INDEMNITY
     ------------------------------

     A.   Provider shall obtain and maintain in full force and effect and
          throughout the term of this Agreement such policies of general
          liability, professional liability and other insurance of the types and
          amounts as are reasonably and customarily  carried by pharmacies with
          respect to their operations.  Provider shall obtain and maintain
          during the term of this Agreement, comprehensive general liability
          insurance coverage in the amount of at least $1,000,000 per
          occurrence, including pharmacist's professional liability insurance,
          for protection from claims for bodily injury and personal injury to
          Members from Provider's operation under this Agreement.  By signing
          this Agreement, Provider represents that these insurance requirements
          are being met.  Provider shall furnish not less than 30 days' prior
          written notice to ESI in the event of termination or material
          modification of any such policies of insurance which renders Provider
          non-compliant with the foregoing.  Upon ESI's request, Provider shall
          provide ESI with evidence of such insurance coverage satisfactory to
          ESI.  If the insurance purchased to satisfy the requirements of this
          Section is of the "claims made" variety, Provider shall purchase an
          extended period of indemnity so that ESI is protected from any and all
          claims brought against ESI for a period of not less than three years
          subsequent to the date of termination of this Agreement.

     B.   With respect to any prescription orders filled by Provider, ESI shall
          not be liable or suffer loss for any claim, injury, demand, or
          judgment of any kind whatsoever arising out of the sale, compounding,
          dispensing, manufacturing, consultation or use of any prescription
          drug or any service provided by Provider pursuant to this Agreement.
          Regardless of the insurance coverage required herein above, Provider
          shall indemnify, defend and hold harmless ESI, its officers, directors
          and employees, against the full amount of any and all loss, expense,
          claim, or damage (including expert and professional fees and attorneys
          fees) arising out of or attributable to any of the foregoing.

     C.   With respect to any prescription orders that are referred by Provider
          to ESI for fulfillment, Provider shall not be liable or suffer loss
          for any claim, injury, demand, or judgment of any kind whatsoever
          arising out of the sale, drug or any service provided by ESI in
          fulfilling such prescription order.  ESI shall indemnify, defend and
          hold harmless Provider, its officers, directors and employees, against
          the full amount of any and all loss, expense, claim, or damage
          (including expert and professional fees and attorneys fees) arising
          out of or attributable to any of the foregoing as related to such
          prescriptions dispensed by ESI.

     D.   If any claim, injury, demand, or judgment (collectively, an
          "Indemnified Claim"), is asserted against a person entitled to
          indemnification hereunder (an "Indemnified Party") in respect of which
          the Indemnified Party proposes to demand indemnification from the
          other party (the "Indemnifying Party") pursuant to Sections 4.B or 4.C
          above, such Indemnified Party will promptly notify the Indemnifying
          Party in writing.  No failure of an Indemnified Party to so notify the
          Indemnifying Party shall relieve the Indemnifying Party from the
          obligation to indemnify the Indemnified Party unless and to the extent
          the Indemnifying Party is actually prejudiced by such failure.  Such
          Indemnified Party will accord the Indemnifying Party the opportunity
          to assume entire control for the defense, compromise or settlement of
          any such Indemnified Claim through its own counsel and at its own
          expense; provided that no such compromise or settlement shall include
                   --------
          any non-monetary terms and conditions
<PAGE>

          applicable to such Indemnified Party without the consent of the
          Indemnified Party, which consent shall not be unreasonably withheld or
          delayed. Notwithstanding the foregoing, the Indemnified Party may
          retain its own counsel at its own expense (the Indemnifying Party
          shall only be liable for the reasonable cost of one such counsel for
          all Indemnified Parties) if (i) the Indemnifying Party, within fifteen
          (15) days after notice of any Indemnified Claim, fails to assume the
          defense of such Indemnified Claim or (ii) the representation of both
          the Indemnifying Party and the Indemnified Party would, in the
          reasonable judgment of the parties, be inappropriate due to actual or
          potential conflicting interests between them. If the Indemnifying
          Party does not assume entire control of the defense, compromise or
          settlement of such Indemnified Claim, the Indemnified Party may
          compromise or settle any such Indemnified Claim. Provider and ESI each
          agrees to reasonably cooperate with respect to the defense of any
          Indemnified Claim, at the Indemnifying Party's expense.appropriate
          taxing authority. Provider shall be solely responsible for any


6.   RECORDS
     -------

     Provider shall maintain medical, financial and administrative records
     relating to Members and their prescriptions for Covered Medications in
     accordance with applicable law and as required for quality assurance and
     peer review programs for a minimum of 5 years from the date any such
     prescription is dispensed.  The parties agree that such records shall be
     treated as confidential so as to comply with all applicable state and
     Federal laws regarding the confidentiality of patient records.  Provider
     shall permit ESI or a third party authorized by ESI to inspect, review,
     audit and reproduce, during regular business hours and without charge, any
     business, financial and prescription records maintained by Provider
     pertaining to ESI, Members or this Agreement as ESI deems necessary to
     determine compliance with the terms of this Agreement.
<PAGE>

7.   QUALITY ASSURANCE
     -----------------

     Provider shall cooperate and participate with ESI in any and all quality
     assurance procedures, peer review, credentialing process, audit systems and
     any complaint resolution procedures established by ESI or required by a
     Sponsor from time to time, and Provider shall abide by, comply with and
     carry out all determinations resulting from such processes or procedures.

8.   ADVERTISING, MARKETING AND RESERVATION OF RIGHTS
     ------------------------------------------------

     Subject to compliance with Provider's trademark quality control guidelines,
     ESI may use Provider's name, URL and description of services for purposes
     of advertising or marketing prescription drug programs in all media,
     including any website operated by ESI, subject to compliance with
     Provider's trademark quality control guidelines.  ESI reserves the
     exclusive rights to, and control of, the use of the name "Express Scripts,
     "PERx" and all other names, symbols and service marks presently existing or
     hereinafter adopted by ESI. Provider shall not advertise or use any names,
     symbols or trademarks of ESI in any advertising or promotional materials or
     otherwise without the prior written consent of ESI.  It is understood and
     agreed that any decal incorporating an ESI servicemark or logo is solely
     for on-line screen display by Provider in connection with its performance
     under this Agreement and that all such use and display shall terminate upon
     termination of the Agreement.

9.   TERM
     ----

     A.   The term of this Agreement shall commence on the Effective Date and
          continue for five (5) years, unless terminated as provided in this
          Section 9.

     B.   Notwithstanding any provision to the contrary, the parties hereto
          agree that in the event either (i) Provider, on the one hand, or (ii)
          ESI, on the other, shall default in performance of any of their
          respective obligations under this Agreement and good faith efforts to
          cure such default have not begun within 10 days after the receipt of
          written notice thereof, the nondefaulting party shall have the right
          by further written notice to the defaulting party to terminate this
          Agreement effective as of any future designated date, not less than 30
          days from the date of the termination notice.

     C.   ESI shall have the right to automatically and immediately terminate
          this Agreement upon written notice in the event that (i) Provider
          ceases to be licensed by the appropriate licensing authorities, or is
          excluded as a sanction for misconduct from participation in any
          government health care programs, (ii) Provider submits a fraudulent
          prescription drug claim or any information in support thereof, knowing
          it to be fraudulent, (iii) Provider is declared insolvent, goes into
          receivership or bankruptcy or any other action is taken on behalf of
          its  creditors, or (iv) the Operating Agreement is terminated due to
          Provider's breach of such agreement.

10.  MISCELLANEOUS
     -------------

     A.   Any notice required to be given pursuant to the terms hereof shall be
          in writing and sent by ordinary or express mail to the other party at
          the address listed below or to the last reported address of such
          party:
<PAGE>

          If to Express Scripts, Inc., to:
          Attn:  Provider Relations
          13900 Riverport Drive
          Maryland Heights, MO 63043

          with a copy to General Counsel at the same address.

          If to PlanetRx, Inc., to:

          PlanetRx.com, Inc.
          6399 Shelby View Dr. Suite 111
          Memphis, TN 38134
          Attn: Legal

          and to:

          PlanetRx, Inc.
          349 Oyster Point Blvd., Suite 201
          South San Francisco, California 94080
          Attention:  Legal
          Fax:  650-616-1505


     B.   Any reference to the parties in this Agreement shall include, apply
          to, bind and benefit the permitted assigns and successors of the
          parties and any corporation, partnership, individual, or person acting
          in a fiduciary capacity on their behalf.

     C.   This Agreement, including the Exhibit(s) and the Provider Manual,
          constitute the entire understanding of the parties hereto with respect
          to the subject matter hereof and, upon execution by the parties,
          supersedes all prior oral or written agreements between the parties
          with respect to the subject matter hereof.  No modification,
          alteration or waiver of any term, covenant or condition of this
          Agreement shall be valid unless agreed to in writing by both parties,
          except as hereinafter set forth.  Notwithstanding the foregoing,
          Provider and ESI agree that ESI may amend this Agreement to comply
          with any changes required or suggested by the appropriate regulatory
          authorities in the course of discharging their responsibilities under
          applicable laws and regulations.  ESI shall furnish Provider with
          written notice of such amendments.  In the event any such amendment
          constitutes a material  change  in the terms of the Agreement that is
          unacceptable to Provider, Provider may elect to terminate this
          Agreement by giving written notice of such election to terminate to
          ESI within 20  days of receipt of amendment, and such termination
          shall be effective  no earlier than 180 days after receipt of written
          notice by ESI.  If Provider does not so elect to terminate this
          Agreement within such 20-day period, such amendment will be deemed
          approved by Provider and ESI and shall automatically become a part of
          this Agreement.  Provider further agrees that ESI may amend the
          Provider Manual and all policies and procedures of ESI, in its sole
          discretion, and such amendment shall not require consent of Provider.

     D.   Provider and ESI each acknowledge that in the performance of the
          services to be rendered hereunder, each Party will have access to
          certain confidential business information regarding the other,
          including but not limited to the following: trade secrets,
<PAGE>

          know-how and nonpublic information that relates to research,
          development, software programming, concepts, designs, procedures,
          purchasing, accounting, engineering, marketing, merchandising,
          selling, business plans or strategies, inventions, source code,
          pricing and other financial and contractual arrangements with Sponsors
          and vendors, manuals, marketing strategies, customer lists, Member
          information protectable under the laws of the United States or any
          other nation, state or jurisdiction (including, but not limited to,
          any foreign equivalents thereto) (collectively, the "Confidential
          Information"). The receiving party shall not disclose or use or enable
          anyone else to disclose or use, in whole or in part, any such
          Confidential Information other than for the purpose of providing the
          services to be provided hereunder and shall promptly return all
          Confidential Information to the providing party upon request. The
          obligations set forth in Section 10.D above shall not apply to any
          Confidential Information to the extent it: (a) is approved by prior
          written authorization of the disclosing party for release by the
          receiving party; (b) is disclosed in order to comply with a judicial
          order issued by a court of competent jurisdiction, in which event the
          receiving party shall give prior written notice to the disclosing
          party of such disclosure as soon as practicable and shall cooperate
          with the disclosing party in using all reasonable efforts to obtain an
          appropriate protective order or equivalent, provided that the
          information shall continue to be Confidential Information to the
          extent it is covered by such protective order or equivalent; (c)
          becomes generally available to the public through any means other than
          a breach by the receiving party of its obligations under this
          Agreement; (d) was in the possession of the receiving party without
          obligation of confidentiality prior to receipt or disclosure under
          this Agreement as evidenced by written records made prior to such
          receipt or disclosure; (e) is developed independently by the receiving
          party without the use of or benefit from any of the Confidential
          Information of the other party or without breach of this Agreement, as
          evidenced by records of the receiving party; or (f) is required to be
          disclosed by any national securities exchange, by government rule or
          regulation (e.g., in connection with a securities filing) or by any
          other provisions of applicable law, provided that the receiving party
                                              --------
          gives the disclosing party advance written notice (to the extent
          practicable) of the disclosure and cooperates with the disclosing
          party in any reasonable attempt to limit the scope of the required
          disclosure. In any dispute over whether information is Confidential
          Information under this Agreement, it will be the burden of the
          receiving party to show that such contested information falls within
          the exceptions set forth in this Section.

     E.   Provider further agrees during the term of this Agreement and for a
          period of one year thereafter it will not solicit the trade or
          patronage of any of the Sponsors or potential sponsors of ESI with
          respect to prescription drug programs, services, .products or other
          matters referred to in this Agreement without ESI's prior written
          consent.  Notwithstanding termination of this Agreement, the rights
          and obligations of the parties under this Subsection shall remain in
          full force and effect for a period of one year following termination.

     F.   This Agreement shall be construed and governed in all respects
          according to the internal laws in the State of Missouri.

     G.   The relationship created hereunder is that of independent contractors
          and nothing herein shall create or be deemed to create an agency,
          partnership or joint venture relationship between the parties.  No
          provision of this Agreement or any part of any Sponsor's Prescription
          Drug Program shall be construed to require any pharmacist to dispense
          any
<PAGE>

          Covered Medication to any Member if, in the pharmacist's reasonable
          professional judgment, such Covered Medication should not be dispensed
          to such person. In such event, Provider agrees to notify ESI of the
          circumstances of the decision not to dispense such Covered Medication.

     H.   No waiver of a breach of any covenant or condition shall be construed
          to be a waiver of any subsequent breach.  No act, delay or omission
          done, suffered, or permitted by the parties shall be deemed to exhaust
          or impair any right, remedy or power of the parties hereunder.

     I.   This Agreement will be enforced to the fullest extent permitted by
          applicable law.  If for any reason any provision of this Agreement is
          held to be invalid or unenforceable to any extent, then: (i) such
          provision will be interpreted, construed or reformed to the extent
          reasonably required to render the same valid, enforceable and
          consistent with the original intent underlying such provision; (ii)
          such provision will be void to the extent it is held to be invalid or
          unenforceable; (iii) such provision will remain in effect to the
          extent that it is not invalid or unenforceable; and (iv) such
          invalidity or unenforceability will not affect any other provision of
          this Agreement or any other agreement between the parties.

     J.   This Agreement shall not be assigned, in whole or in part, by either
          party without the prior written consent of the other, except in
          connection with an acquisition of a party or of all or substantially
          all of a party's assets, provided, that in any such case the assignee
                                   --------
          agrees in writing to be bound by all of the obligations of the
          assignor hereunder.

     IN WITNESS WHEREOF, the undersigned have executed this Provider Agreement
as of the day and year first above written.

PLANETRX.COM, INC.                           EXPRESS SCRIPTS, INC.



By:                                          By:
   -------------------------                    ------------------------
Name:                                        Name:
     -----------------------                      ----------------------
Title:                                       Title:
      ----------------------                       ---------------------
<PAGE>

                                   EXHIBIT A
                                   ---------


                                      FEES


          Reimbursement Rates.  The reimbursement rates (i.e., rates at which
          -------------------
     ESI shall pay Provider) for 30 or fewer days Internet Pharmacy
     prescriptions dispensed to ESI Members by Provider shall be the lesser of:

          (A)  The following rates for the applicable networks:

               [*]

               [*]

               [*]

               [*]

               [*]

               [*]

          or

          (B)  [*]






---------------------
*   Confidential treatment has been requested for certain portions which have
been blacked out in the copy of the exhibit filed with the Securities and
Exchange Commission. The omitted information has been filed separately with the
Securities and Exchange Commission pursuant to the application for confidential
treatment.
<PAGE>

                                   EXHIBIT B
                                   ---------

                             PERFORMANCE STANDARDS
                             ---------------------

For prescriptions dispensed by Provider, the following performance standards
will apply:

1. Mail Service Prescription Accuracy
--------------------------------------------------------------------------------

Standard
--------

While Provider strives for 100 percent accuracy, Provider guarantees [*] percent
accuracy in dispensing the correct drug, at the correct strength and at the
correct dosage, unless the error is a prescriber error. This standard will be
measured [*].

Guarantee
---------
Provider places [*] percent of the dispensing fee at risk, if performance is
below the stated standard.


2. Turnaround time for routine prescriptions
--------------------------------------------------------------------------------

Standard
--------

Provider guarantees dispensing and shipping (or return) of [*] percent of all
fillable prescriptions not subject to intervention within an average of [*]
business days of receipt of the order at Provider.  This standard will be
measured and reported [*]. "Interventions" include all calls to members or
prescribers to clarify the prescriber's direction, to obtain consent for generic
or therapeutic substitution, or otherwise.

Guarantee
---------
Provider places [*] percent of the dispensing fee at risk, if performance is
below the stated standard for [*] or more.


3. Turnaround time for prescriptions subject to intervention
--------------------------------------------------------------------------------

Standard
--------

Provider guarantees dispensing and shipping (or return) of [*] percent of all
prescriptions subject to intervention within an average of [*] business days of
receipt of the order at Provider, if the prescriber provides a response on the
initial attempts at intervention. This standard will be measured [*].

Guarantee
---------
Provider places [*] percent of the dispensing fee at risk if performance is
below the stated standard for [*] or more.




---------------------
*   Confidential treatment has been requested for certain portions which have
been blacked out in the copy of the exhibit filed with the Securities and
Exchange Commission. The omitted information has been filed separately with the
Securities and Exchange Commission pursuant to the application for confidential
treatment.