<PAGE>

"EXHIBIT 10.21"

[LETTERHEAD OF ABN-AMRO]

                             CASH POOLING AGREEMENT

              CASH CONCENTRATION AND BALANCE COMPENSATION FACILITY

CONFIDENTIAL
Parexel International Holding B.V.
Herman Heijermansweg 20
1077 WL Amsterdam
(the "MASTER ACCOUNT HOLDER")

                                                    Friday, September 14th, 2001

Dear Sirs,

ABN AMRO Bank N.V., (the "BANK"), acting through certain of its branches is
pleased to offer the following facilities (each a "FACILITY") to you and to the
other Account Holders with respect to your Accounts, subject to the terms and
conditions set out below.

Unless otherwise defined in this letter, terms defined in the Agreement with
respect to Interest Compensation (the "AGREEMENT") between the Bank and the
Account Holders have the same meaning in this letter. References, in relation to
an Account Holder to a "New Accountholder", to "Other Account", and to "
Account", are to those items which relate to one another and which appear
against the Account Holder's name in the Account Schedule or in any Accession
Agreement (Appendix I) or Account Agreement (Appendix II)(as they may be amended
from time to time).

CASH CONCENTRATION         A facility (the "CASH CONCENTRATION FACILITY") made
FACILITY                   available to the relevant Account Holders by the Bank
                           on the Accounts up to the relevant maximum amount in
                           euros specified in relation to those Accounts
                           together.

BALANCE COMPENSATION       A facility (the "BALANCE COMPENSATION FACILITY") made
FACILITY                   available to the relevant Account Holders by the Bank
                           on the Accounts up to the total of the credit
                           balances present on those Accounts at the same time
                           (in addition to the Cash Concentration Facility).
                           Each Account Holder individually is fully empowered
                           to use the Balance Compensation Facility, except to
                           the extent that the Account Holders and the Bank have
                           agreed relevant sub-limits on one or more of the
                           Accounts.

UTILISATION                Each Facility may be used as follows:

                           (a)      by way of a fluctuating overdraft;

                           (b)      on the relevant Account or relevant group of
                                    Accounts together; and

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                                       2

[LETTERHEAD OF ABN-AMRO]

                           (c)      up to the relevant maximum amount in euros
                                    specified in relation to that Account or
                                    group of Accounts together

PURPOSE                    (a)      Each Facility may only be used for the
                                    purposes of cash management in connection
                                    with the normal operation of the interest
                                    compensation arrangement established under
                                    the Agreement and is not available for use
                                    as working capital.

                           (b)      Without prejudice to the other provisions of
                                    this letter, the Bank needs not permit usage
                                    of a Facility where to do so would cause any
                                    Account to exceed the limit applicable to
                                    that Account.

AVAILABILITY               (a)      It is hereby expressly understood and agreed
                                    upon between the parties that each Facility
                                    is granted until further notice and may be
                                    revoked or cancelled by the Bank at any
                                    time.

                           (b)      The Bank will have the right at any time to
                                    refuse withdrawals in whole or in part under
                                    the Balance Compensation Facility, even when
                                    made to the debit of credit accounts, if the
                                    result would be that the overall debit
                                    balance on the Accounts is no longer covered
                                    fully by the credit balances and the Cash
                                    Concentration Facility on such Accounts
                                    together.

                           (c)      If the Balance Compensation Facility is
                                    actually used for any amount, the Bank is
                                    authorised to block credit balances for the
                                    same amount on the Accounts, regardless of
                                    whether the relevant Account Holder is
                                    itself the user of the Balance Compensation
                                    Facility and without prejudice to the other
                                    rights which the Bank can exercise in
                                    respect of those credit balances as pledgee
                                    or otherwise.

INTEREST                   (a)      Interest under this letter shall be payable
                                    on the Cash Concentration Facility at the
                                    relevant frequency and the relevant debit
                                    interest rate. When any part of the Cash
                                    Concentration Facility falls to be repaid,
                                    interest shall also be payable on the amount
                                    repaid.

                           (b)      If an Account Holder fails to pay any amount
                                    on the due date, the Account Holder shall on
                                    demand from time to time pay interest on the
                                    overdue amount from the due date up to the
                                    date of payment (both before and after
                                    judgment) at a rate equal to the relevant
                                    penalty interest rate.

                           (c)      Interest shall accrue from day to day and be
                                    calculated in accordance with the normal
                                    practice for euros. The Bank may debit any
                                    Account of an Account Holder with the amount
                                    of interest payable by that Account Holder.

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                                       3

[LETTERHEAD OF ABN-AMRO]

PAYMENTS                   (a)      All payments by an Account Holder must be
                                    made in accordance with the normal practice
                                    for the relevant currency without set-off or
                                    counterclaim and free of deduction on
                                    account of tax or other charges.

                           (b)      If an Account Holder is compelled by law or
                                    any competent authority to make a deduction
                                    or withholding, it shall promptly pay to the
                                    Bank or the relevant Account Affiliate such
                                    additional amount as will result in the net
                                    amount received by the Bank or the relevant
                                    Account Affiliate being equal to the full
                                    amount which would have been receivable had
                                    there been no deduction or withholding.

REPAYMENT                  (a)      It is hereby expressly understood and agreed
                                    upon between the parties that each Facility
                                    is repayable in full upon demand made, for
                                    any reason, by the Bank at any time.

                           (b)      Any usage of the Cash Concentration Facility
                                    must be reduced to zero at least once in
                                    each week.

                           (c)      If an Account is cancelled as an Account,
                                    each relevant Facility must be immediately
                                    repaid in full.

CONDITIONS PRECEDENT       It is a requirement for the utilisation of each
                           Facility that:

                           (a)      each Account Holder agrees to be jointly and
                                    severally liable, in accordance with Article
                                    2 of the Agreement, for any and all of the
                                    Account Holders' obligations under this
                                    letter.

                           (b)      the Bank has received the Agreement, duly
                                    executed by or on behalf of each of the
                                    parties to it;

                           (c)      the Bank has received a copy of any other
                                    document required by the terms of the
                                    Agreement referred to above; and

                           (d)      the Bank has received a copy of any other
                                    document required by the Bank.

                           Each copy document shall be certified by an officer
                           of the relevant Account Holder as being correct,
                           complete and in full force and effect on the date
                           they are delivered.

WARRANTIES AND             Each of the Account Holders warrants to the Bank on
UNDERTAKING                the date of this letter and on each date on which it
                           is in force that:

                           (a)      this letter constitutes its legal, valid and
                                    binding obligations in accordance with its
                                    terms;

                           (b)      this letter is within its powers and has
                                    been duly authorised by it;

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                                       4

[LETTERHEAD OF ABN-AMRO]

                           (c)      this letter does not and will not breach its
                                    constitutional documents or any deed or
                                    agreement by which it is bound;

                           (d)      all necessary consents and authorisations in
                                    relation to this letter have been obtained
                                    and are in force; and

                           (e)      (save for security interests in favour of
                                    the Bank) it is solely and absolutely
                                    entitled to the credit balances on each
                                    Account in respect of which a Facility is
                                    made available and undertakes at all times
                                    to keep the same free from any security
                                    interest and free of interests, rights or
                                    claims of third parties of any kind.

CHANGES TO ACCOUNT         (a)      The Master Account Holder may join a New
HOLDERS AND ACCOUNTS                Account Holder as a party to each relevant
                                    Facility by delivering to the Bank a duly
                                    completed Accession Agreement, executed by
                                    each of the parties to it, together with,
                                    unless waived by the Bank in writing, the
                                    relevant documents in respect of the New
                                    Account Holder required under the Agreement.

                           (b)      An Account Holder which withdraws from the
                                    interest compensation arrangement in
                                    accordance with Article 4 of the Agreement
                                    shall be automatically excluded from further
                                    usage of each relevant Facility, and shall
                                    immediately discharge in full all its
                                    liabilities under each relevant Facility.

                           (c)      An Account maintained at the Bank may:

                                    (i)      be designated an Account on which
                                             the Cash Concentration Facility or
                                             Balance Compensation Facility is
                                             available; or

                                    (ii)     be cancelled as such an Account, so
                                             that it is excluded from the Cash
                                             Concentration Facility or Balance
                                             Compensation Facility.

                                    in each case by the Master Account Holder
                                    and the relevant Account Holder delivering
                                    to the Bank a duly completed Account
                                    Agreement executed by each of the parties to
                                    it.

                           (d)      The Main Account may be cancelled by the
                                    Master Account Holder delivering to the Bank
                                    such form of agreement as the Bank may
                                    require.

                           (e)      Any cancellation of an Account under
                                    paragraph (c) or (d) above shall be without
                                    prejudice to any liabilities owed by or to
                                    the relevant Account Holder under the
                                    Facility in respect of that Account.

MISCELLANEOUS              (a)      In case of any inconsistency between the
                                    terms and conditions of this letter and its
                                    enclosures and the Agreement, any Harmonised
                                    Business Conditions, General Banking
                                    Conditions or other arrangements existing
                                    between any Account Holder and

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                                       5

[LETTERHEAD OF ABN-AMRO]

                                    the Bank the terms and conditions of this
                                    letter and its enclosures shall prevail.

                           (b)      Each Account Holder shall pay to the Bank
                                    all reasonable costs and expenses (including
                                    legal fees on a full indemnity basis)
                                    incurred by the Bank in connection with (i)
                                    any breach by the Account Holder of any
                                    provision of this letter, (ii) the exercise
                                    and preservation of the Bank's rights under
                                    this letter and (iii) any legal proceedings
                                    or disputes between any Account Holder and a
                                    third party where the Bank becomes involved
                                    in such disputes or proceedings.

                           (c)      None of the Account Holders may assign,
                                    novate or otherwise transfer any of its
                                    rights and/or obligations under this letter
                                    without the prior written consent of the
                                    Bank.

                           (d)      If a provision of this letter is or becomes
                                    Illegal, invalid or unenforceable in any
                                    jurisdiction, that shall not affect the
                                    validity or enforceability in that
                                    jurisdiction of any other provision of this
                                    letter or the validity or enforceability in
                                    other jurisdictions of that or any other
                                    provision of this letter.

                           (e)      The rights of the Bank under this letter (i)
                                    may be exercised as often as necessary, (ii)
                                    are cumulative and not exclusive of its
                                    rights under the general law, and (iii) may
                                    be waived only in writing and specifically.
                                    Delay in exercising or non-exercise of any
                                    such right is not a waiver of that right.

GOVERNING                  (a)      This letter is governed by Dutch law. For
LAW/JURISDICTION                    the benefit of the Bank each Account Holder
                                    submits to the non-exclusive jurisdiction of
                                    the court of the Netherlands (and the courts
                                    of each other jurisdiction notified to the
                                    Master Account Holder from time to time by
                                    the Bank) and appoints as its agent for
                                    service of process in relation to any
                                    proceedings before the courts of the
                                    Netherlands, the person nominated as its
                                    process agent under its name on the
                                    execution page of this letter. Each of the
                                    Bank and the Account Affiliates submits to
                                    the exclusive jurisdiction of The courts of
                                    the Netherlands.

                           (b)      Each party waives objection to the Dutch
                                    court on grounds of inconvenient forum or
                                    otherwise as regards proceedings in
                                    connection with this letter and agrees that
                                    a judgement or order of a Dutch court in
                                    connection with this letter is conclusive
                                    and binding on it and may be enforced
                                    against it in the courts of any other
                                    jurisdiction.

ACCEPTANCE                 This offer is open for acceptance until two months
                           after the date of this letter. The Master Account
                           holder shall confirm the acceptance of the terms and
                           conditions of this letter by returning the attached
                           duplicate copy to the bank, duly executed by each of
                           the Account Holders.

HARMONISED BUSINESS        The Harmonised Business Conditions agreed between the
CONDITIONS                 Account Holders and the Bank, a copy of which the
                           Account Holders acknowledge having received, will be
                           applicable.

                                   Version 1.1
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                                       6

[LETTERHEAD OF ABN-AMRO]

Yours faithfully,
ABN AMRO BANK N.V.

name: A. C. Udi                     signature: /s/ A. C. Udi
                                               ----------------

name: [ILLEGIBLE]                   signature: /s/ [ILLEGIBLE]
                                               ----------------
We agree to the above.

Yours faithfully,

PAREXEL INTERNATIONAL HOLDING B.V.
name: P. Rietman                    signature: /s/ Peter Rietman
     ----------------                          -----------------

PAREXEL NEDERLAND B.V.
name:                               signature: /s/ Peter Rietman
     ----------------                          -----------------

PAREXEL SWEDEN AB
name:                               signature: /s/ Peter Rietman
     ----------------                          -----------------

MIRAI PLACEBO B.V.
name:                               signature: /s/ Peter Rietman
     ----------------                          -----------------

PAREXEL INTERNATIONAL SARL
name:                               signature: /s/ Josef H. Von Rickenbach
     ----------------                          ---------------------------

PAREXEL INTERNATIONAL SRL
name:                               signature: /s/ Josef H. Von Rickenbach
     ----------------                          ---------------------------

PAREXEL UNTERNEHMENSBETEILUNG GMBH
name:                               signature: /s/ Josef H. Von Rickenbach
     ----------------                          ---------------------------

PAREXEL INTERNATIONAL LIMITED
name:                               signature: /s/ Josef H. Von Rickenbach
     ----------------                          ---------------------------

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<PAGE>

                                       7

[LETTERHEAD OF ABN-AMRO]

PAREXEL MMS EUROPE LIMITED
name:                               signature: /s/ [ILLEGIBLE]
     ----------------                          ----------------

PAREXEL INTERNATIONAL CORPORATION
name:                               signature: /s/ Josef H. Von Rickenbach
     ----------------                          ---------------------------

                                   Version 1.1

<PAGE>

THE NETHERLANDS                               ACCOUNT SCHEDULE - ACCOUNT DETAILS

<TABLE>
<CAPTION>
                     Master
                    Account/
Bank / Affiliate    Account             Account Holder           Account number   Currency
----------------    -------             --------------           --------------   --------
<S>                 <C>           <C>                            <C>              <C>
AA Amsterdam        Account                  PAREXEL                595148263       EUR
                                      International Holding
                                              B.V.
AA Amsterdam        Account                  PAREXEL                595152783       EUR
                                       International SARL
AA Amsterdam        Account                  PAREXEL                595152902       EUR
                                        International SRL
AA Amsterdam        Account                  PAREXEL                516727036       EUR
                                      International Holding
                                              B.V.
AA Amsterdam        Account                  PAREXEL                595153372       EUR
                                            Nederland
                                              B.V.
AA Amsterdam        Account                  PAREXEL                595172504       EUR
                                           Nederland
                                              B.V.
AA Amsterdam        Account             PAREXEL Norway AS           595153488       EUR
AA Amsterdam        Account             PAREXEL Norway AS           599415609       EUR
AA Amsterdam        Account             PAREXEL Polska SP           599414677       EUR
                                              ZOO
AA Amsterdam        Account             PAREXEL Sweden AB           595153569       EUR
AA Amsterdam        Account             Mirai Placebo B.V.          467790744       EUR
AA Amsterdam        Account          PAREXEL Baltics AS             595137756       EUR
AA Amsterdam        Account                  PAREXEL                599251778       EUR
                                      International Holding
                                              B.V.
AA Amsterdam        Account               PAREXEL Denmark           473468255       EUR
                                          sub of PAREXEL
                                           Nederland B.V.
AA Amsterdam        Account                PAREXEL MMS              503327573       EUR
                                           Europe Ltd
AA Amsterdam        Account              PAREXEL Belgium            570568153       EUR
                                              Sprl
AA Amsterdam        Account                  PAREXEL                628217641       EUR
                                       International ETT SL
AA Amsterdam        Account                  PAREXEL                628218079       EUR
                                         International SL
AA Amsterdam        Account                  PAREXEL                595153585       EUR
                                          Unternehmens
                                        beteiligung GmbH
AA Amsterdam        Account              PAREXEL Hungary            595139434       EUR
                                           [ILLEGIBLE]
AA Amsterdam        Account            PAREXEL Nederland            489735428       NLG
                                              B.V.

<CAPTION>

                                                                                       Trigger & Target
                                           Interest Conditions                        -------------------
                     --------------------------------------------------------------   Upper trigger (UT)      Credit facility
                                                                         Settlement    Lower trigger(LT)    -----------------
Bank / Affiliate     Debit rate        Credit rate       Penalty rate     frequency   Target balance (TB)   ID/ON       Limit
----------------     ----------        -----------       ------------     ---------   -------------------   -----       -----
<S>                 <C>               <C>               <C>              <C>          <C>                   <C>      <C>
AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp   EONIA + 200 bp   Quarterly                            Na     EUR 12 mln


AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na

AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na

AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na


AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na


AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na


AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na
AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na
AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na

AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na
AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na
AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na
AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na


AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na


AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na

AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na

AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na

AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na

AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na


AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na

AA Amsterdam        EONIA + 75 bp     EONIA -/- 75 bp       Na           Quarterly                            Na
</TABLE>


                                                                     Page 1 of 3

                                                                     [ILLEGIBLE]
<PAGE>

THE NETHERLANDS                               ACCOUNT SCHEDULE - ACCOUNT DETAILS

<TABLE>
<CAPTION>
                   Master
                   Account/
Bank / Affiliate   Account         Account Holder         Account number    Currency
------------------------------------------------------------------------------------
<S>                <C>         <C>                        <C>               <C>
AA Amsterdam       Account           PAREXEL                 595148352        GBP
                               International Holding
                                      B.V.
AA Amsterdam       Account           PAREXEL                 469784156        GBP
                               International Holding
                                      B.V.
AA Amsterdam       Account           PAREXEL                 595140602        GBP
                               International Limited
AA Amsterdam       Account         PAREXEL  MMS              595153003        GBP
                                 Europe Limited
AA Amsterdam       Account           PAREXEL                 595148484        USD
                               International Holding
                                      B.V.
AA Amsterdam       Account           PAREXEL                 610907921        USD
                                  International
                                   Corporation
AA Amsterdam       Account            PAREXEL                469774754        USD
                               International Holding
                                       B.V.
AA Amsterdam       Account            PAREXEL                595152139        USD
                                 International Inc.
AA Amsterdam       Account            PAREXEL                595142575        USD
                               International Limited
AA Amsterdam       Account            PAREXEL                595152597        USD
                               International Pty
AA Amsterdam       Account           PAREXEL, MMS            595153011        USD
                                   Europe Limited
AA Amsterdam       Account        PAREXEL,Russia AS          595153526        USD

<CAPTION>
                                                                                         Trigger & Target    Credit facility
                                         Interest Conditions                            ------------------   ---------------
                    -----------------------------------------------------------------   Upper trigger(UT)
                                                                           Settlement   Lower trigger(LT)
Bank / Affiliate       Debit rate          Credit rate      Penalty rate   frequency    Target balance(TB)   ID/ON     Limit
----------------    ----------------     ----------------   ------------   ----------   ------------------   -----     -----
<S>                 <C>                  <C>                <C>            <C>          <C>                  <C>       <C>
AA Amsterdam        Pakketcode + 150     Pakketcode -/- 150      Na         Quarterly                         Na


AA Amsterdam        Pakketcode + 150     Pakketcode -/- 150      Na         Quarterly                         Na


AA Amsterdam        Pakketcode + 150     Pakketcode -/- 150      Na         Quarterly                         Na

AA Amsterdam        Pakketcode + 150     Pakketcode -/- 150      Na         Quarterly                         Na

AA Amsterdam        Pakketcode   USD     Pakketcode   USD        Na         Quarterly                         Na


AA Amsterdam        Pakketcode   USD     Pakketcode   USD        Na         Quarterly                         Na


AA Amsterdam        Pakketcode   USD     Pakketcode   USD        Na         Quarterly                         Na


AA Amsterdam        Pakketcode   USD     Pakketcode   USD        Na         Quarterly                         Na

AA Amsterdam        Pakketcode   USD     Pakketcode   USD        Na         Quarterly                         Na

AA Amsterdam        Pakketcode   USD     Pakketcode   USD        Na         Quarterly                         Na

AA Amsterdam        Pakketcode   USD     Pakketcode   USD        Na         Quarterly                         Na

AA Amsterdam        Pakketcode   USD     Pakketcode   USD        Na         Quarterly                         Na
</TABLE>

                                                                     Page 2 of 3

                                                                     [ILLEGIBLE]
<PAGE>

Date 30-6-2003

Signed by:

/s/ [Peter Rietman]
-----------------

(The Master Account Holder for itself and on behalf of each Account Holder)

Date 25-6-2003

Signed by:

/s/ [ILLEGIBLE]
-----------------

[ILLEGIBLE]

                                                                     Page 3 of 3

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