<PAGE>

                                                                   EXHIBIT 10.35

                               SUBSIDIARY GUARANTY

                  This SUBSIDIARY GUARANTY is entered into as of February 13,
2004 by THE UNDERSIGNED (each a "Guarantor" and collectively, "Guarantors") in
favor of and for the benefit of Credit Suisse First Boston as Collateral Agent
for and representative of (in such capacity herein called "Guarantied Party")
the Agents (as hereinafter defined) and the financial institutions party to the
Credit Agreement ("Lenders") referred to below, and, subject to subsection 3.12,
for the benefit of the other Beneficiaries (as hereinafter defined).

                                    RECITALS

                  A.       Express Scripts, Inc., a Delaware corporation
("Company"), has entered into that certain Credit Agreement dated as of February
13, 2004 with the financial institutions listed therein as Lenders, Credit
Suisse First Boston, and Citigroup Global Markets Inc., as Joint Lead Arrangers,
Credit Suisse First Boston, as Administrative Agent and Collateral Agent,
Citigroup Global Markets Inc., as Syndication Agent and Bank of America, Bank
One, N.A. and U.S. Bank National Association, as Co-Documentation Agent
(collectively "Agents") and Lenders (as amended, supplemented or otherwise
modified from time to time, the "Credit Agreement"; capitalized terms defined
therein and not otherwise defined herein being used herein as therein defined).

                  B.       A portion of the proceeds of the Loans may be
advanced to Guarantors and thus the Guarantied Obligations (as hereinafter
defined) are being incurred for and will inure to the benefit of Guarantors
(which benefits are hereby acknowledged).

                  C.       It is a condition precedent to the making of the
initial Loans under the Credit Agreement that Company's obligations thereunder
be guarantied by Guarantors.

                  D.       Guarantors are willing irrevocably and
unconditionally to guaranty such obligations of Company.

                  NOW, THEREFORE, based upon the foregoing and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, and in order to induce Lenders and Guarantied Party to enter into
the Credit Agreement and to make Loans and other extensions of credit
thereunder, Guarantors hereby agree as follows:

SECTION 1. DEFINITIONS

                  1.1      CERTAIN DEFINED TERMS. As used in this Guaranty, the
following terms shall have the following meanings unless the context otherwise
requires:

                  "Beneficiaries" means Guarantied Party, Agents and Lenders.

                  "Guarantied Obligations" has the meaning assigned to that term
         in subsection 2.1.

                  "Guaranty" means this Subsidiary Guaranty, as it may be
         amended, supplemented or otherwise modified from time to time.

<PAGE>

                  "payment in full", "paid in full" or any similar term means
         payment in full of the Guarantied Obligations, including all principal,
         interest, costs, fees and expenses (including reasonable legal fees and
         expenses) of Beneficiaries as required under the Loan Documents.

                  1.2      INTERPRETATION.

                  (a)      References to "Sections" and "subsections" shall be
to Sections and subsections, respectively, of this Guaranty unless otherwise
specifically provided.

                  (b)      In the event of any conflict or inconsistency between
the terms, conditions and provisions of this Guaranty and the terms, conditions
and provisions of the Credit Agreement, the terms, conditions and provisions of
this Guaranty shall prevail.

SECTION 2. THE GUARANTY

                  2.1      GUARANTY OF THE GUARANTIED OBLIGATIONS. Subject to
the provisions of subsection 2.2(a), Guarantors jointly and severally hereby
irrevocably and unconditionally guaranty the due and punctual payment in full of
all Guarantied Obligations when the same shall become due, whether at stated
maturity, by required prepayment, declaration, acceleration, demand or otherwise
(including amounts that would become due but for the operation of the automatic
stay under Section 362(a) of the Bankruptcy Code, 11 U.S.C. Section 362(a)). The
term "Guarantied Obligations" is used herein in its most comprehensive sense and
includes:

                  (a)      any and all Obligations of Company, in each case now
         or hereafter made, incurred or created, whether absolute or contingent,
         liquidated or unliquidated, whether due or not due, and however arising
         under or in connection with the Credit Agreement and the other Loan
         Documents, including those arising under successive borrowing
         transactions under the Credit Agreement which shall either continue the
         Obligations of Company or from time to time renew them after they have
         been satisfied and including interest which, but for the filing of a
         petition in bankruptcy with respect to Company, would have accrued on
         any Guarantied Obligations, whether or not a claim is allowed against
         Company for such interest in the related bankruptcy proceeding; and

                  (b)      those expenses set forth in subsection 2.8 hereof.

                  2.2      LIMITATION ON AMOUNT GUARANTIED; CONTRIBUTION BY
GUARANTORS. (a) Anything contained in this Guaranty to the contrary
notwithstanding, if any Fraudulent Transfer Law (as hereinafter defined) is
determined by a court of competent jurisdiction to be applicable to the
obligations of any Guarantor under this Guaranty, such obligations of such
Guarantor hereunder shall be limited to a maximum aggregate amount equal to the
largest amount that would not render its obligations hereunder subject to
avoidance as a fraudulent transfer or conveyance under Section 548 of Title 11
of the United States Code or any applicable provisions of comparable state law
(collectively, the "Fraudulent Transfer Laws"), in each case after giving effect
to all other liabilities of such Guarantor, contingent or otherwise, that are
relevant under the Fraudulent Transfer Laws (specifically excluding, however,
any liabilities of

                                      -2-
<PAGE>

such Guarantor (x) in respect of intercompany indebtedness to Company or other
affiliates of Company to the extent that such indebtedness would be discharged
in an amount equal to the amount paid by such Guarantor hereunder and (y) under
any guaranty of Subordinated Indebtedness which guaranty contains a limitation
as to maximum amount similar to that set forth in this subsection 2.2(a),
pursuant to which the liability of such Guarantor hereunder is included in the
liabilities taken into account in determining such maximum amount) and after
giving effect as assets to the value (as determined under the applicable
provisions of the Fraudulent Transfer Laws) of any rights to subrogation,
reimbursement, indemnification or contribution of such Guarantor pursuant to
applicable law or pursuant to the terms of any agreement (including any such
right of contribution under subsection 2.2(b).

                  (b)      Guarantors under this Guaranty together desire to
allocate among themselves in a fair and equitable manner, their obligations
arising under this Guaranty. Accordingly, in the event any payment or
distribution is made on any date by any Guarantor under this Guaranty (a
"Funding Guarantor") that exceeds its Fair Share (as defined below) as of such
date, that Funding Guarantor shall be entitled to a contribution from each of
the other Guarantors in the amount of such other Guarantor's Fair Share
Shortfall (as defined below) as of such date, with the result that all such
contributions will cause each Guarantor's Aggregate Payments (as defined below)
to equal its Fair Share as of such date. "Fair Share" means, with respect to a
Guarantor as of any date of determination, an amount equal to (i) the ratio of
(x) the Adjusted Maximum Amount (as defined below) with respect to such
Guarantor to (y) the aggregate of the Adjusted Maximum Amounts with respect to
all Guarantors multiplied by (ii) the aggregate amount paid or distributed on or
before such date by all Funding Guarantors under this Guaranty in respect of the
obligations guarantied. "Fair Share Shortfall" means, with respect to a
Guarantor as of any date of determination, the excess, if any, of the Fair Share
of such Guarantor over the Aggregate Payments of such Guarantor. "Adjusted
Maximum Amount" means, with respect to a Guarantor as of any date of
determination, the maximum aggregate amount of the obligations of such Guarantor
under this Guaranty determined as of such date, in the case of any Guarantor, in
accordance with subsection 2.2(a); provided that, solely for purposes of
calculating the "Adjusted Maximum Amount" with respect to any Guarantor for
purposes of this subsection 2.2(b), any assets or liabilities of such Guarantor
arising by virtue of any rights to subrogation, reimbursement or indemnification
or any rights to or obligations of contribution hereunder shall not be
considered as assets or liabilities of such Guarantor. "Aggregate Payments"
means, with respect to a Guarantor as of any date of determination, an amount
equal to (i) the aggregate amount of all payments and distributions made on or
before such date by such Guarantor in respect of this Guaranty (including in
respect of this subsection 2.2(b)) minus (ii) the aggregate amount of all
payments received on or before such date by such Guarantor from the other
Guarantors as contributions under this subsection 2.2(b). The amounts payable as
contributions hereunder shall be determined as of the date on which the related
payment or distribution is made by the applicable Funding Guarantor. The
allocation among Guarantors of their obligations as set forth in this subsection
2.2(b) shall not be construed in any way to limit the liability of any Guarantor
hereunder.

                  2.3      PAYMENT BY GUARANTORS; APPLICATION OF PAYMENTS.
Subject to the provisions of subsection 2.2(a), Guarantors hereby jointly and
severally agree, in furtherance of

                                      -3-
<PAGE>

the foregoing and not in limitation of any other right which any Beneficiary
may have at law or in equity against any Guarantor by virtue hereof, that upon
the failure of Company to pay any of the Guarantied Obligations when and as the
same shall become due, whether at stated maturity, by required prepayment,
declaration, acceleration, demand or otherwise (including amounts that would
become due but for the operation of the automatic stay under Section 362(a) of
the Bankruptcy Code, 11 U.S.C. Section 362(a)), Guarantors will upon demand pay,
or cause to be paid, in cash, to Guarantied Party for the ratable benefit of
Beneficiaries, an amount equal to the sum of the unpaid principal amount of all
Guarantied Obligations then due as aforesaid, accrued and unpaid interest on
such Guarantied Obligations (including interest which, but for the filing of a
petition in bankruptcy with respect to Company, would have accrued on such
Guarantied Obligations, whether or not a claim is allowed against Company for
such interest in the related bankruptcy proceeding) and all other Guarantied
Obligations then owed to Beneficiaries as aforesaid. All such payments shall be
applied promptly from time to time by Guarantied Party as provided in subsection
2.4D of the Credit Agreement.

                  2.4      LIABILITY OF GUARANTORS ABSOLUTE. Each Guarantor
agrees that its obligations hereunder are irrevocable, absolute, independent and
unconditional and shall not be affected by any circumstance which constitutes a
legal or equitable discharge of a guarantor or surety other than payment in full
of the Guarantied Obligations. In furtherance of the foregoing and without
limiting the generality thereof, each Guarantor agrees as follows:

                  (a)      This Guaranty is a guaranty of payment when due and
         not of collectibility.

                  (b)      Guarantied Party may enforce this Guaranty upon the
         occurrence of an Event of Default under the Credit Agreement
         notwithstanding the existence of any dispute between Company and any
         Beneficiary with respect to the existence of such Event of Default.

                  (c)      The obligations of each Guarantor hereunder are
         independent of the obligations of Company under the Loan Documents and
         the obligations of any other guarantor (including any other Guarantor)
         of the obligations of Company under the Loan Documents, and a separate
         action or actions may be brought and prosecuted against such Guarantor
         whether or not any action is brought against Company or any of such
         other guarantors and whether or not Company is joined in any such
         action or actions.

                  (d)      Payment by any Guarantor of a portion, but not all,
         of the Guarantied Obligations shall in no way limit, affect, modify or
         abridge any Guarantor's liability for any portion of the Guarantied
         Obligations which has not been paid. Without limiting the generality of
         the foregoing, if Guarantied Party is awarded a judgment in any suit
         brought to enforce any Guarantor's covenant to pay a portion of the
         Guarantied Obligations, such judgment shall not be deemed to release
         such Guarantor from its covenant to pay the portion of the Guarantied
         Obligations that is not the subject of such suit, and such judgment
         shall not, except to the extent satisfied by such Guarantor, limit,
         affect, modify or abridge any other Guarantor's liability hereunder in
         respect of the Guarantied Obligations.

                                      -4-
<PAGE>

                  (e)      Any Beneficiary, upon such terms as it deems
         appropriate, without notice or demand and without affecting the
         validity or enforceability of this Guaranty or giving rise to any
         reduction, limitation, impairment, discharge or termination of any
         Guarantor's liability hereunder, from time to time may (i) renew,
         extend, accelerate, increase the rate of interest on, or otherwise
         change the time, place, manner or terms of payment of the Guarantied
         Obligations, (ii) settle, compromise, release or discharge, or accept
         or refuse any offer of performance with respect to, or substitutions
         for, the Guarantied Obligations or any agreement relating thereto
         and/or subordinate the payment of the same to the payment of any other
         obligations; (iii) request and accept other guaranties of the
         Guarantied Obligations and take and hold security for the payment of
         this Guaranty or the Guarantied Obligations; (iv) release, surrender,
         exchange, substitute, compromise, settle, rescind, waive, alter,
         subordinate or modify, with or without consideration, any security for
         payment of the Guarantied Obligations, any other guaranties of the
         Guarantied Obligations, or any other obligation of any Person
         (including any other Guarantor) with respect to the Guarantied
         Obligations; (v) enforce and apply any security now or hereafter held
         by or for the benefit of such Beneficiary in respect of this Guaranty
         or the Guarantied Obligations and direct the order or manner of sale
         thereof, or exercise any other right or remedy that such Beneficiary
         may have against any such security, in each case as such Beneficiary in
         its discretion may determine consistent with the Credit Agreement and
         any applicable security agreement, including foreclosure on any such
         security pursuant to one or more judicial or nonjudicial sales, whether
         or not every aspect of any such sale is commercially reasonable, and
         even though such action operates to impair or extinguish any right of
         reimbursement or subrogation or other right or remedy of any Guarantor
         against Company or any security for the Guarantied Obligations; and
         (vi) exercise any other rights available to it under the Loan
         Documents.

                  (f)      This Guaranty and the obligations of Guarantors
         hereunder shall be valid and enforceable and shall not be subject to
         any reduction, limitation, impairment, discharge or termination for any
         reason (other than payment in full of the Guarantied Obligations),
         including the occurrence of any of the following, whether or not any
         Guarantor shall have had notice or knowledge of any of them: (i) any
         failure or omission to assert or enforce or agreement or election not
         to assert or enforce, or the stay or enjoining, by order of court, by
         operation of law or otherwise, of the exercise or enforcement of, any
         claim or demand or any right, power or remedy (whether arising under
         the Loan Documents, at law, in equity or otherwise) with respect to the
         Guarantied Obligations or any agreement relating thereto, or with
         respect to any other guaranty of or security for the payment of the
         Guarantied Obligations; (ii) any rescission, waiver, amendment or
         modification of, or any consent to departure from, any of the terms or
         provisions (including provisions relating to events of default) of the
         Credit Agreement, any of the other Loan Documents or any agreement or
         instrument executed pursuant thereto, or of any other guaranty or
         security for the Guarantied Obligations, in each case whether or not in
         accordance with the terms of the Credit Agreement or such Loan Document
         or any agreement relating to such other guaranty or security; (iii) the
         Guarantied Obligations, or any agreement relating thereto, at any time
         being found to be illegal, invalid or unenforceable in any respect;
         (iv) the application of payments received

                                      -5-
<PAGE>

         from any source (other than payments received pursuant to the other
         Loan Documents or from the proceeds of any security for the Guarantied
         Obligations) to the payment of indebtedness other than the Guarantied
         Obligations, even though any Beneficiary might have elected to apply
         such payment to any part or all of the Guarantied Obligations; (v) any
         Beneficiary's consent to the change, reorganization or termination of
         the corporate structure or existence of Company or any of its
         Subsidiaries and to any corresponding restructuring of the Guarantied
         Obligations; (vi) any failure to perfect or continue perfection of a
         security interest in any collateral which secures any of the Guarantied
         Obligations; (vii) any defenses, set-offs or counterclaims which
         Company may allege or assert against any Beneficiary in respect of the
         Guarantied Obligations, including failure of consideration, breach of
         warranty, payment, statute of frauds, statute of limitations, accord
         and satisfaction and usury; and (viii) any other act or thing or
         omission, or delay to do any other act or thing, which may or might in
         any manner or to any extent vary the risk of any Guarantor as an
         obligor in respect of the Guarantied Obligations.

                  2.5      WAIVERS BY GUARANTORS. Each Guarantor hereby waives,
for the benefit of Beneficiaries:

                  (a)      any right to require any Beneficiary, as a condition
         of payment or performance by such Guarantor, to (i) proceed against
         Company, any other guarantor (including any other Guarantor) of the
         Guarantied Obligations or any other Person, (ii) proceed against or
         exhaust any security held from Company, any such other guarantor or any
         other Person, (iii) proceed against or have resort to any balance of
         any deposit account or credit on the books of any Beneficiary in favor
         of Company or any other Person, or (iv) pursue any other remedy in the
         power of any Beneficiary whatsoever;

                  (b)      any defense arising by reason of the incapacity, lack
         of authority or any disability or other defense of Company including
         any defense based on or arising out of the lack of validity or the
         unenforceability of the Guarantied Obligations or any agreement or
         instrument relating thereto or by reason of the cessation of the
         liability of Company from any cause other than payment in full of the
         Guarantied Obligations;

                  (c)      any defense based upon any statute or rule of law
         which provides that the obligation of a surety must be neither larger
         in amount nor in other respects more burdensome than that of the
         principal;

                  (d)      any defense based upon any Beneficiary's errors or
         omissions in the administration of the Guarantied Obligations, except
         behavior which amounts to bad faith;

                  (e)      (i) any principles or provisions of law, statutory or
         otherwise, which are or might be in conflict with the terms of this
         Guaranty and any legal or equitable discharge of such Guarantor's
         obligations hereunder, (ii) the benefit of any statute of limitations
         affecting such Guarantor's liability hereunder or the enforcement
         hereof, (iii) any rights to set-offs, recoupments and counterclaims,
         and (iv) promptness, diligence and any

                                      -6-
<PAGE>

         requirement that any Beneficiary protect, secure, perfect or insure any
         security interest or lien or any property subject thereto;

                  (f)      notices, demands, presentments, protests, notices of
         protest, notices of dishonor and notices of any action or inaction,
         including acceptance of this Guaranty, notices of default under the
         Credit Agreement or any agreement or instrument related thereto,
         notices of any renewal, extension or modification of the Guarantied
         Obligations or any agreement related thereto, notices of any extension
         of credit to Company and notices of any of the matters referred to in
         subsection 2.4 and any right to consent to any thereof; and

                  (g)      any defenses or benefits that may be derived from or
         afforded by law which limit the liability of or exonerate guarantors or
         sureties, or which may conflict with the terms of this Guaranty.

                  2.6      GUARANTORS' RIGHTS OF SUBROGATION, CONTRIBUTION, ETC.
Each Guarantor hereby waives, until the Guarantied Obligations shall have been
indefeasibly paid in full and the Commitments shall have terminated and all
Letters of Credit shall have expired or been cancelled, any claim, right or
remedy, direct or indirect, that such Guarantor now has or may hereafter have
against Company or any of its assets in connection with this Guaranty or the
performance by such Guarantor of its obligations hereunder, in each case whether
such claim, right or remedy arises in equity, under contract, by statute under
common law or otherwise and including (a) any right of subrogation,
reimbursement or indemnification that such Guarantor now has or may hereafter
have against Company, (b) any right to enforce, or to participate in, any claim,
right or remedy that any Beneficiary now has or may hereafter have against
Company, and (c) any benefit of, and any right to participate in, any collateral
or security now or hereafter held by any Beneficiary. In addition, until the
Guarantied Obligations shall have been indefeasibly paid in full and the
Commitments shall have terminated and all Letters of Credit shall have expired
or been cancelled, each Guarantor shall withhold exercise of any right of
contribution such Guarantor may have against any other guarantor (including any
other Guarantor) of the Guarantied Obligations (including any such right of
contribution under subsection 2.2(b)). Each Guarantor further agrees that, to
the extent the waiver or agreement to withhold the exercise of its rights of
subrogation, reimbursement, indemnification and contribution as set forth herein
is found by a court of competent jurisdiction to be void or voidable for any
reason, any rights of subrogation, reimbursement or indemnification such
Guarantor may have against Company or against any collateral or security, and
any rights of contribution such Guarantor may have against any such other
guarantor, shall be junior and subordinate to any rights any Beneficiary may
have against Company, to all right, title and interest any Beneficiary may have
in any such collateral or security, and to any right any Beneficiary may have
against such other guarantor. If any amount shall be paid to any Guarantor on
account of any such subrogation, reimbursement, indemnification or contribution
rights at any time when all Guarantied Obligations shall not have been paid in
full, such amount shall be held in trust for Guarantied Party on behalf of
Beneficiaries and shall forthwith be paid over to Guarantied Party for the
benefit of Beneficiaries to be credited and applied against the Guarantied
Obligations, whether matured or unmatured, in accordance with the terms hereof.

                                      -7-
<PAGE>

                  2.7      SUBORDINATION OF OTHER OBLIGATIONS. Any indebtedness
of Company or any Guarantor now or hereafter held by any Guarantor (the "Obligee
Guarantor") is hereby subordinated in right of payment to the Guarantied
Obligations, and any such indebtedness collected or received by the Obligee
Guarantor after an Event of Default has occurred and is continuing shall be held
in trust for Guarantied Party on behalf of Beneficiaries and shall forthwith be
paid over to Guarantied Party for the benefit of Beneficiaries to be credited
and applied against the Guarantied Obligations but without affecting, impairing
or limiting in any manner the liability of the Obligee Guarantor under any other
provision of this Guaranty.

                  2.8      EXPENSES. Guarantors jointly and severally agree to
pay, or cause to be paid, on demand, and to save Beneficiaries harmless against
liability for, any and all costs and expenses (including reasonable fees and
disbursements of counsel and reasonable allocated costs of internal counsel)
incurred or expended by any Beneficiary in connection with the enforcement of or
preservation of any rights under this Guaranty.

                  2.9      CONTINUING GUARANTY. This Guaranty is a continuing
guaranty and shall remain in effect until all of the Guarantied Obligations
shall have been paid in full and the Commitments shall have terminated and all
Letters of Credit shall have expired or been cancelled. Each Guarantor hereby
irrevocably waives any right to revoke this Guaranty as to future transactions
giving rise to any Guarantied Obligations.

                  2.10     RIGHTS CUMULATIVE. The rights, powers and remedies
given to Beneficiaries by this Guaranty are cumulative and shall be in addition
to and independent of all rights, powers and remedies given to Beneficiaries by
virtue of any statute or rule of law or in any of the other Loan Documents or
any agreement between any Guarantor and any Beneficiary or Beneficiaries or
between Company and any Beneficiary or Beneficiaries. Any forbearance or failure
to exercise, and any delay by any Beneficiary in exercising, any right, power or
remedy hereunder shall not impair any such right, power or remedy or be
construed to be a waiver thereof, nor shall it preclude the further exercise of
any such right, power or remedy.

                  2.11     BANKRUPTCY; POST-PETITION INTEREST; REINSTATEMENT OF
GUARANTY. (a) So long as any Guarantied Obligations remain outstanding, no
Guarantor shall, without the prior written consent of Guarantied Party acting
pursuant to the instructions of Requisite Lenders, commence or join with any
other Person in commencing any bankruptcy, reorganization or insolvency
proceedings of or against Company. The obligations of Guarantors under this
Guaranty shall not be reduced, limited, impaired, discharged, deferred,
suspended or terminated by any proceeding, voluntary or involuntary, involving
the bankruptcy, insolvency, receivership, reorganization, liquidation or
arrangement of Company or by any defense which Company may have by reason of the
order, decree or decision of any court or administrative body resulting from any
such proceeding.

                  (b)      Each Guarantor acknowledges and agrees that any
interest on any portion of the Guarantied Obligations which accrues after the
commencement of any proceeding referred to in clause (a) above (or, if interest
on any portion of the Guarantied Obligations ceases to accrue by operation of
law by reason of the commencement of said proceeding, such interest as would
have accrued on such portion of the Guarantied Obligations if said proceedings
had not

                                      -8-
<PAGE>

been commenced) shall be included in the Guarantied Obligations because it is
the intention of Guarantors and Beneficiaries that the Guarantied Obligations
which are guarantied by Guarantors pursuant to this Guaranty should be
determined without regard to any rule of law or order which may relieve Company
of any portion of such Guarantied Obligations. Guarantors will permit any
trustee in bankruptcy, receiver, debtor in possession, assignee for the benefit
of creditors or similar person to pay Guarantied Party, or allow the claim of
Guarantied Party in respect of, any such interest accruing after the date on
which such proceeding is commenced.

                  (c)      In the event that all or any portion of the
Guarantied Obligations are paid by Company, the obligations of Guarantors
hereunder shall continue and remain in full force and effect or be reinstated,
as the case may be, in the event that all or any part of such payment(s) are
rescinded or recovered directly or indirectly from any Beneficiary as a
preference, fraudulent transfer or otherwise, and any such payments which are so
rescinded or recovered shall constitute Guarantied Obligations for all purposes
under this Guaranty.

                  2.12     NOTICE OF EVENTS. As soon as Guarantor obtains
knowledge thereof, Guarantor shall give Guarantied Party written notice of any
condition or event which has resulted in (a) a material adverse change in the
financial condition of Guarantor or Company or (b) any Event of Default or
Potential Event of Default.

                  2.13     SET OFF. In addition to any other rights any
Beneficiary may have under law or under this Guaranty, such Beneficiary is
authorized at any time or from time to time while an Event of Default has
occurred and is continuing, without notice (any such notice being hereby
expressly waived), to set off and to appropriate and to apply any and all
deposits (general or special, including indebtedness evidenced by certificates
of deposit, whether matured or unmatured) and any other indebtedness of such
Beneficiary owing to Guarantor and any other property of Guarantor held by any
Beneficiary to or for the credit or the account of Guarantor against and on
account of the Guarantied Obligations and liabilities of Guarantor to any
Beneficiary under this Guaranty.

SECTION 3. MISCELLANEOUS

                  3.1      SURVIVAL OF WARRANTIES. All agreements,
representations and warranties made herein shall survive the execution and
delivery of this Guaranty and the other Loan Documents and any increase in the
Commitments under the Credit Agreement.

                  3.2      NOTICES. Any communications between Guarantied Party
and any Guarantor and any notices or requests provided herein to be given may be
given by mailing the same, postage prepaid, or by telex, facsimile transmission
or cable to each such party at its address set forth in the Credit Agreement, on
the signature pages hereof or to such other addresses as each such party may in
writing hereafter indicate. Any notice, request or demand to or upon Guarantied
Party or any Guarantor shall not be effective until received.

                  3.3      SEVERABILITY. In case any provision in or obligation
under this Guaranty shall be invalid, illegal or unenforceable in any
jurisdiction, the validity, legality and

                                      -9-
<PAGE>

enforceability of the remaining provisions or obligations, or of such provision
or obligation in any other jurisdiction, shall not in any way be affected or
impaired thereby.

                  3.4      AMENDMENTS AND WAIVERS. No amendment, modification,
termination or waiver of any provision of this Guaranty, and no consent to any
departure by any Guarantor therefrom, shall in any event be effective without
the written concurrence of Guarantied Party and, in the case of any such
amendment or modification, each Guarantor against whom enforcement of such
amendment or modification is sought. Any such waiver or consent shall be
effective only in the specific instance and for the specific purpose for which
it was given.

                  3.5      HEADINGS. Section and subsection headings in this
Guaranty are included herein for convenience of reference only and shall not
constitute a part of this Guaranty for any other purpose or be given any
substantive effect.

                  3.6      APPLICABLE LAW; RULES OF CONSTRUCTION. THIS GUARANTY
AND THE RIGHTS AND OBLIGATIONS OF GUARANTORS AND BENEFICIARIES HEREUNDER SHALL
BE GOVERNED BY, AND SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE
INTERNAL LAWS OF THE STATE OF NEW YORK. The rules of construction set forth in
subsection 1.3 of the Credit Agreement shall be applicable to this Guaranty
mutatis mutandis.

                  3.7      SUCCESSORS AND ASSIGNS. This Guaranty is a continuing
guaranty and shall be binding upon each Guarantor and its respective successors
and assigns. This Guaranty shall inure to the benefit of Beneficiaries and their
respective successors and assigns. No Guarantor shall assign this Guaranty or
any of the rights or obligations of such Guarantor hereunder without the prior
written consent of all Lenders. Any Beneficiary may, without notice or consent,
assign its interest in this Guaranty in whole or in part. The terms and
provisions of this Guaranty shall inure to the benefit of any transferee or
assignee of any Loan, and in the event of such transfer or assignment the rights
and privileges herein conferred upon such Beneficiary shall automatically extend
to and be vested in such transferee or assignee, all subject to the terms and
conditions hereof.

                  3.8      CONSENT TO JURISDICTION AND SERVICE OF PROCESS. ALL
JUDICIAL PROCEEDINGS BROUGHT AGAINST ANY GUARANTOR ARISING OUT OF OR RELATING TO
THIS GUARANTY, OR ANY OBLIGATIONS HEREUNDER, MAY BE BROUGHT IN ANY STATE OR
FEDERAL COURT OF COMPETENT JURISDICTION IN THE STATE, COUNTY AND CITY OF NEW
YORK. BY EXECUTING AND DELIVERING THIS AGREEMENT, EACH GUARANTOR, FOR ITSELF AND
IN CONNECTION WITH ITS PROPERTIES, IRREVOCABLY

                  (I) ACCEPTS GENERALLY AND UNCONDITIONALLY THE NONEXCLUSIVE
         JURISDICTION AND VENUE OF SUCH COURTS;

                  (II) WAIVES ANY DEFENSE OF FORUM NON CONVENIENS WITH RESPECT
         TO ANY STATE OR FEDERAL COURT OF COMPETENT JURISDICTION IN THE STATE,
         COUNTY AND CITY OF NEW YORK;

                                      -10-
<PAGE>

                  (III) AGREES THAT SERVICE OF ALL PROCESS IN ANY SUCH
         PROCEEDING IN ANY SUCH COURT MAY BE MADE BY REGISTERED OR CERTIFIED
         MAIL, RETURN RECEIPT REQUESTED, TO SUCH GUARANTOR AT ITS ADDRESS
         PROVIDED IN ACCORDANCE WITH SUBSECTION 3.2;

                  (IV) AGREES THAT SERVICE AS PROVIDED IN CLAUSE (III) ABOVE IS
         SUFFICIENT TO CONFER PERSONAL JURISDICTION OVER SUCH GUARANTOR IN ANY
         SUCH PROCEEDING IN ANY SUCH COURT, AND OTHERWISE CONSTITUTES EFFECTIVE
         AND BINDING SERVICE IN EVERY RESPECT;

                  (V) AGREES THAT BENEFICIARIES RETAIN THE RIGHT TO SERVE
         PROCESS IN ANY OTHER MANNER PERMITTED BY LAW OR TO BRING PROCEEDINGS
         AGAINST SUCH GUARANTOR IN THE COURTS OF ANY OTHER JURISDICTION; AND

                  (VI) AGREES THAT THE PROVISIONS OF THIS SUBSECTION 3.8
         RELATING TO JURISDICTION AND VENUE SHALL BE BINDING AND ENFORCEABLE TO
         THE FULLEST EXTENT PERMISSIBLE UNDER NEW YORK GENERAL OBLIGATIONS LAW
         SECTION 5-1402 OR OTHERWISE.

                  3.9      WAIVER OF TRIAL BY JURY. EACH GUARANTOR AND, BY ITS
ACCEPTANCE OF THE BENEFITS HEREOF, EACH BENEFICIARY EACH HEREBY AGREES TO WAIVE
ITS RESPECTIVE RIGHTS TO A JURY TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED UPON
OR ARISING OUT OF THIS GUARANTY. The scope of this waiver is intended to be all
encompassing of any and all disputes that may be filed in any court and that
relate to the subject matter of this transaction, including contract claims,
tort claims, breach of duty claims and all other common law and statutory
claims. Each Guarantor and, by its acceptance of the benefits hereof, each
Beneficiary, each (i) acknowledges that this waiver is a material inducement for
such Guarantor and Beneficiaries to enter into a business relationship, that
such Guarantor and Beneficiaries have already relied on this waiver in entering
into this Guaranty or accepting the benefits thereof, as the case may be, and
that each will continue to rely on this waiver in their related future dealings
and (ii) further warrants and represents that each has reviewed this waiver with
its legal counsel, and that each knowingly and voluntarily waives its jury trial
rights following consultation with legal counsel. THIS WAIVER IS IRREVOCABLE,
MEANING THAT IT MAY NOT BE MODIFIED EITHER ORALLY OR IN WRITING (OTHER THAN BY A
MUTUAL WRITTEN WAIVER SPECIFICALLY REFERRING TO THIS SUBSECTION 3.9 AND EXECUTED
BY GUARANTIED PARTY AND EACH GUARANTOR), AND THIS WAIVER SHALL APPLY TO ANY
SUBSEQUENT AMENDMENTS, RENEWALS, SUPPLEMENTS OR MODIFICATIONS TO THIS GUARANTY.
In the event of litigation, this Guaranty may be filed as a written consent to a
trial by the court.

                  3.10     NO OTHER WRITING. This writing is intended by
Guarantors and Beneficiaries as the final expression of this Guaranty and is
also intended as a complete and

                                      -11-
<PAGE>

exclusive statement of the terms of their agreement with respect to the matters
covered hereby. No course of dealing, course of performance or trade usage, and
no parol evidence of any nature, shall be used to supplement or modify any terms
of this Guaranty. There are no conditions to the full effectiveness of this
Guaranty.

                  3.11     FURTHER ASSURANCES. At any time or from time to time,
upon the request of Guarantied Party, Guarantors shall execute and deliver such
further documents and do such other acts and things as Guarantied Party may
reasonably request in order to effect fully the purposes of this Guaranty.

                  3.12     ADDITIONAL GUARANTORS. The initial Guarantors
hereunder shall be such of the Subsidiaries of Company as are signatories hereto
on the date hereof. From time to time subsequent to the date hereof, additional
Subsidiaries of Company may become parties hereto, as additional Guarantors
(each an "Additional Guarantor"), by executing a counterpart of this Guaranty.
Upon delivery of any such counterpart to Administrative Agent, notice of which
is hereby waived by Guarantors, each such Additional Guarantor shall be a
Guarantor and shall be as fully a party hereto as if such Additional Guarantor
were an original signatory hereof. Each Guarantor expressly agrees that its
obligations arising hereunder shall not be affected or diminished by the
addition or release of any other Guarantor hereunder, nor by any election of
Administrative Agent not to cause any Subsidiary of Company to become an
Additional Guarantor hereunder. This Guaranty shall be fully effective as to any
Guarantor that is or becomes a party hereto regardless of whether any other
Person becomes or fails to become or ceases to be a Guarantor hereunder.

                  3.13     COUNTERPARTS; EFFECTIVENESS. This Guaranty may be
executed in any number of counterparts and by the different parties hereto in
separate counterparts, each of which when so executed and delivered shall be
deemed to be an original for all purposes; but all such counterparts together
shall constitute but one and the same instrument. This Guaranty shall become
effective as to each Guarantor upon the execution of a counterpart hereof by
such Guarantor (whether or not a counterpart hereof shall have been executed by
any other Guarantor) and receipt by Guarantied Party of written or telephonic
notification of such execution and authorization of delivery thereof.

                  3.14     GUARANTIED PARTY AS AGENT.

                  (a)      Guarantied Party has been appointed to act as
Guarantied Party hereunder by Lenders. Guarantied Party shall be obligated, and
shall have the right hereunder, to make demands, to give notices, to exercise or
refrain from exercising any rights, and to take or refrain from taking any
action, solely in accordance with this Guaranty and the Credit Agreement;
provided that Guarantied Party shall exercise, or refrain from exercising, any
remedies hereunder in accordance with the instructions of Requisite Lenders.

                  (b)      Guarantied Party shall at all times be the same
Person that is Administrative Agent under the Credit Agreement. Written notice
of resignation by Administrative Agent pursuant to subsection 9.5 of the Credit
Agreement shall also constitute notice of resignation as Guarantied Party under
this Guaranty; removal of Administrative Agent

                                      -12-
<PAGE>

pursuant to subsection 9.5 of the Credit Agreement shall also constitute removal
as Guarantied Party under this Guaranty; and appointment of a successor Agent
pursuant to subsection 9.5 of the Credit Agreement shall also constitute
appointment of a successor Guarantied Party under this Guaranty. Upon the
acceptance of any appointment as Agent under subsection 9.5 of the Credit
Agreement by a successor Administrative Agent, that successor Administrative
Agent shall thereupon succeed to and become vested with all the rights, powers,
privileges and duties of the retiring or removed Guarantied Party under this
Guaranty, and the retiring or removed Guarantied Party under this Guaranty shall
promptly (i) transfer to such successor Guarantied Party all sums held
hereunder, together with all records and other documents necessary or
appropriate in connection with the performance of the duties of the successor
Guarantied Party under this Guaranty, and (ii) take such other actions as may be
necessary or appropriate in connection with the assignment to such successor
Guarantied Party of the rights created hereunder, whereupon such retiring or
removed Guarantied Party shall be discharged from its duties and obligations
under this Guaranty. After any retiring or removed Guarantied Party's
resignation or removal hereunder as Guarantied Party, the provisions of this
Guaranty shall inure to its benefit as to any actions taken or omitted to be
taken by it under this Guaranty while it was Guarantied Party hereunder.

                  [Remainder of page intentionally left blank]

                                      -13-
<PAGE>

                  IN WITNESS WHEREOF, each of the undersigned Guarantors has
caused this Guaranty to be duly executed and delivered by its officer thereunto
duly authorized as of the date first written above.

                                           CENTRAL FILL, INC.
                                           CFI OF NEW JERSEY, INC.
                                           CURASCRIPT PHARMACY, INC.
                                           CURASCRIPT PBM SERVICES, INC.
                                           DIVERSIFIED PHARMACEUTICAL
                                              SERVICES, INC.
                                           EXPRESS SCRIPTS SALES
                                              DEVELOPMENT CO.
                                           IBIOLOGIC, INC.
                                           IVTX, INC.
                                           VALUE HEALTH, INC.
                                           ESI MAIL PHARMACY SERVICE,
                                              INC.
                                           EXPRESS SCRIPTS UTILIZATION
                                              MANAGEMENT CO.
                                           EXPRESS SCRIPTS SPECIALTY
                                              DISTRIBUTION SERVICES, INC.
                                           ESI AIRPORT PROPERTIES, LLC
                                           ESI CLAIMS, INC.
                                           ESI ENTERPRISES, LLC
                                           ESI PARTNERSHIP
                                           ESI REALTY, LLC
                                           NATIONAL PRESCRIPTION
                                              ADMINISTRATORS, INC.
                                           PHOENIX MARKETING GROUP,
                                              L.L.C.
                                           EXPRESS SCRIPTS CANADA
                                              HOLDING CO.
                                           YOURPHARMACY.COM, INC.


                                      By:  /s/ George Paz
                                          --------------------------------------
                                          Name: George Paz
                                          Title: Vice President

                                           ESI RESOURCES, INC.
                                           ESI-GP HOLDINGS, INC.

                                      By:  /s/ Thomas L. Schaefer
                                          --------------------------------------
                                          Name: Thomas L. Schaefer
                                          Title: President

<PAGE>

                  IN WITNESS WHEREOF, the undersigned Additional Guarantor has
caused this Guaranty to be duly executed and delivered by its officer thereunto
duly authorized as of ______________, ____.
S
                                      __________________________________________
                                           (Name of Additional Guarantor)

                                      By:    ___________________________________
                                      Title: ___________________________________

                                      Address: _________________________________
                                             ___________________________________
                                             ___________________________________
                                             ___________________________________