Document:

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                                                                EXHIBIT 10.18(a)

                         AMENDMENT NO. 1 TO SUBLEASE AND
                           SUPPORT SERVICES AGREEMENT

AGREEMENT, dated as of July 1, 1999 between Rittenhouse Financial Services,
Inc., a Delaware corporation ("RFS"), and The Rittenhouse Trust Company, a trust
company and commercial bank organized under the laws of the Commonwealth of
Pennsylvania ("RTC"). Capitalized terms used but not otherwise defined in this
Agreement shall have the meanings ascribed to them in the Sublease (as defined
below) or the Support Services Agreement (as defined below), as the case may be.

WHEREAS, RFS and RTC have entered into a Sublease, dated as of August 31, 1997
(the "Sublease"), and a Support Services Agreement, dated as of August 31, 1997
(the "Support Services Agreement");

WHEREAS, pursuant to the Sublease, since August 31, 1997, RTC has subleased from
RFS certain office space leased by RFS at Two Radnor Corporate Center, Radnor,
Pennsylvania;

WHEREAS, pursuant to the Support Services Agreement, since August 31, 1997, RFS
has made available to RTC certain support services used by RTC in the operation
of its business; and

WHEREAS, RTC has moved its business operations to new premises in Radnor
Corporate Center as a result of its desire to expand, RFS desires to utilize the
space that RTC has vacated, and RFS and RTC desire to amend the terms of the
Sublease and the Support Services Agreement in connection therewith;

NOW THEREFORE, in consideration of the foregoing recitals, the mutual promises
and agreements hereinafter set forth, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, RFS
and RTC hereby agree as follows:

1.   Sublease. The Sublease shall terminate and be of no further force or effect
     (except as provided below with respect to Section 11 of the Sublease) as
     of May 17, 1999 (the "Sublease Termination Date"). RFS shall have no
     obligation to make any portion of the Premises available to RTC for its
     use, and RTC shall have no obligation to pay to RFS any Rent in respect of
     any period, after the Sublease Termination Date. This Agreement shall not
     affect in any way any rights that RFS or RTC may have against the other
     under the Sublease in respect of any actions or events occurring prior to
     the Sublease Termination Date or pursuant to

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     the indemnification provisions of Section 11 of the Sublease. RTC will pay
     Rent to RFS in respect of the period ending on the Sublease Termination
     Date (on a pro-rated basis) in accordance with the past practice of the
     parties. RFS shall notify the Landlord of the termination of the
     Sublease promptly following the Sublease Termination Date.

2.   Support Services Agreement. From and after the Sublease Termination Date,
     Sections 1, 4 and 14 of the Support Services Agreement shall be amended in
     respect of the services to be made available by RFS to RTC thereunder, the
     fees to be paid by RTC to RFS thereunder, and the term of such agreement,
     and replaced in their entirety by the provisions set forth below in
     Paragraphs 3 through 6. The Support Services Agreement, as amended by this
     Agreement, is referred to herein as the "Amended Support Services
     Agreement."

3.   Provided Services. Notwithstanding anything to the contrary contained in
     the Support Services Agreement, from and after the Sublease Termination
     Date, RFS will make available to RTC only the support services set forth on
     Schedule I hereto in accordance with the practices in effect on the date
     hereof or as otherwise specifically set forth in Schedule 1. From and after
     the Sublease Termination Date, RTC will have no obligation to make any
     support services available to RFS.

4.   Fees. Notwithstanding anything to the contrary contained in the Support
     Services Agreement, in consideration of the services to be provided under
     the Amended Support Services Agreement, RTC shall pay to the parent company
     of RFS, The John Nuveen Company ("JNC"), or an affiliate designated by JNC,
     in lieu of the Fixed Annual Fee set forth in the Support Services
     Agreement, an amount equal to six million four hundred twenty-four thousand
     two hundred twenty dollars ($6,424,220), which shall be payable in one
     installment of one million one hundred fifty-six thousand eight hundred
     twenty dollars ($1,156,820) on July 1, 1999 and in five equal quarterly
     installments of one million fifty-three thousand four hundred eighty
     dollars ($1,053,480) on the first business day of each calendar quarter,
     beginning October 1, 1999 and ending October 2, 2000 in each case by wire
     transfer of immediately available funds (the "Revised Fixed Fee"). The
     Revised Fixed Fee shall be payable regardless of whether and to what extent
     any RFS provided services are utilized by RTC hereunder during any calendar
     quarter to which a Revised Fixed Fee payment relates. In consideration of
     the services to be provided by RFS under this Agreement, RTC shall also pay
     to RFS the fee or other charge set forth opposite each such provided
     service on Schedule 1 in respect of RFS provided services actually provided
     and received by RTC during a billing period hereunder, and each RFS
     provided service will be invoiced to RTC in accordance with past practices.

5.   Contiguous Office Space. The requirement to pay fees payable under the
     Amended Support Services Agreement shall not be related in any way to the
     Sublease or to the location of RTC's business operations in space
     contiguous to that of RFS. RFS shall have no obligation to secure
     contiguous office space for

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     RTC in the event that RFS moves its business operations or acquires
     additional office space.

6.   Term. (a) Notwithstanding anything to the contrary contained in the Support
     Services Agreement, the Amended Support Services Agreement shall terminate,
     and RFS shall cease to be obligated to provide services, on the earlier of
     (i) December 31, 2000, (ii) an RTC Default as described in paragraph (b)
     below, and (iii) a material default by RFS hereunder, unless such default
     has been cured by RFS to the reasonable satisfaction of RTC within 30 days
     after receipt of written notice of default from RTC. In the event that the
     Amended Support Services Agreement would otherwise terminate on December
     31, 2000 in accordance with clause (i) of the preceding sentence, RTC shall
     have the right to extend such date to December 31, 2001 by delivering
     written notice of the desire to so extend to RFS no later than November 30,
     2000, together with a payment of one hundred dollars for such extension.
     Upon termination of the Amended Support Services Agreement all payment
     obligations of RTC shall cease except for any accrued and unpaid
     liabilities for the Revised Fixed Fee, for services previously rendered
     and, if applicable, any payment described in paragraph (c) below.

     (b) "RTC Default" means (i) a material default by RTC hereunder, unless
     such default has been cured by RTC to the reasonable satisfaction of RFS
     within 30 days after receipt of written notice of such default, (ii) a
     majority of the outstanding capital stock of RTC ceases to be owned by
     George W. Connell, or a Permitted Transferee (as defined in the
     Inter-Company Agreement among RTC, RFS, JNC and George W. Connell) or (iii)
     the sale, exchange, transfer or other disposition of any outstanding
     capital stock of RTC to a competitor of JNC.

     (c) In the event the Amended Support Services Agreement is terminated
     pursuant to an RTC Default, RTC shall make payment within five business
     days to JNC or an affiliate of JNC by wire transfer of immediately
     available funds of an amount equal to the present value (applying a
     discount rate equal to the then prevailing prime rate of interest announced
     by Morgan Guaranty Trust Company of New York) of the Revised Fixed Fee
     amounts which have not been theretofore paid. In the event of the
     termination of the Amended Support Services Agreement for any reason other
     than (i) an RTC Default or (ii) so long as there has been no continuing RTC
     Default and so long as RTC has not materially breached any of the
     Transaction Documents that is continuing, RFS's willful breach of its
     obligation under the Amended Support Services Agreement to provide
     services, RTC shall continue to pay the Revised Fixed Fee.

7.   Further Assurances. RFS and RTC agree to work together in good faith to
     ensure a smooth transition of the RTC business into new office space and to
     avoid confusion of customers or service providers relating to the
     similarity of the RFS and RTC names. In particular, the parties will work
     together and cooperate in connection with their respective mail room,
     receptionist and record management

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<PAGE>   4

     personnel to take all necessary actions to insure a smooth transition in
     separation of the office space and of the previously shared office
     management functions. The parties also agree to work together to properly
     separate all commingled files held on location or offsite.

8.   No other Changes. Except as modified as set forth above, the provisions of
     the Support Services Agreement shall remain in full force and effect. This
     Agreement shall not affect in any way any of the terms of the agreements
     entered into by RFS and RTC at the time of the acquisition of RFS by JNC or
     subsequent thereto, other than the Sublease and the Support Services
     Agreement.

IN WITNESS WHEREOF, the parties hereto, being duly authorized, have duly
executed and delivered this Agreement.

                                            RITTENHOUSE FINANCIAL SERVICES, INC.

                                            By:
                                               --------------------------------
                                                  Name: Alan G. Berkshire
                                                  Title: Vice President

                                            Date:
                                                 ------------------------------

                                            THE RITTENHOUSE TRUST COMPANY

                                            By:
                                               --------------------------------
                                                  Name:
                                                  Title:

                                            Date:
                                                 ------------------------------

                                            THE JOHN NUVEEN COMPANY

                                            By:
                                               --------------------------------
                                                   Name: Alan G. Berkshire
                                                   Title: Senior Vice President

                                            Date:
                                                 ------------------------------

                                       4<PAGE>   1
                                                                    EXHIBIT 10.4

                         CORPORATE GOVERNANCE AGREEMENT

       This Agreement is entered into as of November 12, 1999 by Stericycle,
Inc., a Delaware corporation (the "Company"), and the Persons whose names are
set forth on the attached Schedule I (collectively, the "Investors").

       A. The Company and the Investors are concurrently closing an Amended and
Restated Series A Convertible Preferred Stock Purchase Agreement, dated
September 26, 1999 (the "Purchase Agreement"), pursuant to the terms and
conditions of which the Company is issuing and selling to the Investors, and the
Investors are purchasing from the Company, 75,000 of Series A Convertible
Preferred Stock (the "Preferred Shares").

       B. The Parties' execution and delivery of this Agreement is a condition
of their respective obligations to close the Purchase Agreement.

       The Parties agree as follows:

       1. DEFINITIONS. Capitalized terms which are used in this Agreement
without being defined have the same meanings that they are given in the Purchase
Agreement. In addition, the following terms have these meanings.

       BOARD OF DIRECTORS or BOARD means the Company's board of directors.

       CONVERTED SHARES means the shares of Common Stock actually received by an
Investor or a Permitted Transferee upon conversion of some or all of the
Preferred Shares.

       INITIAL INTEREST means the aggregate number of shares of Common Stock
into which the Preferred Shares may be converted as of Closing.

       INVESTOR NOMINEE means any person nominated by the Permitted Owners to
serve as a director of the Company pursuant to this Agreement.

       PERMITTED OWNER means (i) an Investor, for as long as the Investor
continues to be the beneficial owner of Shares, and (ii) each Permitted
Transferee, for as long as the Permitted Transferee continues to be the
beneficial owner of Shares.

       PERMITTED TRANSFEREE means (i) any other Investor, (ii) any Affiliate
(including any partner) of any Investor to whom an Investor or another Affiliate
of any Investor Transfers Preferred Shares or Converted Shares, (iii) any other
Person to whom an Investor or an Affiliate of any Investor Transfers Preferred
Shares or Converted Shares with the prior written consent of the Board of
Directors and (iv) any Person to whom a transferee described in clause (iii)
Transfers Preferred or Converted Shares with the prior written consent of the
Board of Directors. In no event shall any Person who acquires Converted Shares
pursuant to a Rule 144 Sale or an offering registered under the Securities Act
be considered a Permitted Transferee. No Transfer otherwise permissible shall be
effective unless the transferee agrees in writing expressly for the Company's
benefit to be bound by the provisions of this Agreement, and in this event, the
transferor shall not be liable for the transferee's performance of its
obligations under this Agreement.

       RULE 144 SALE means a transaction exempt from registration pursuant to
Rule 144 under the Securities Act.

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       SHARES means, at any time, the aggregate number of (i) Converted Shares
then held by the Investor and Permitted Transferees, (ii) Converted Shares that
the Investors and Permitted Transferees then have the right to receive upon a
conversion of all Preferred Shares then held by them and (iii) any other shares
of Common Stock then held by the Investors and Permitted Transferees.

       TRANSFER means to sell, assign, transfer (voluntarily or involuntarily),
exchange (by merger or otherwise) or otherwise dispose of or to grant a lien,
encumbrance, pledge or other form of security interest.

       2.  CORPORATE GOVERNANCE.

       2A. APPOINTMENT OF INVESTOR NOMINEES. Effective as of Closing, the
Company shall increase the size of its Board of Directors from seven directors
to nine directors, and the Board shall appoint two Investor Nominees designated
by the Investors to fill the vacancies created. An Investor Nominee shall serve
on each committee of the Board.

       2B.  MAINTENANCE OF DIRECTORSHIPS.

       (a) For as long as Shares representing at least 50% in the aggregate of
the Initial Interest are beneficially owned by Permitted Owners, Permitted
Owners shall continue to have the right to designate two persons who shall be
the Company's nominees for election to the Company's Board of Directors. The
Company shall nominate each person so designated and shall use reasonable
efforts to have the two nominees of the Permitted Owners elected to its Board of
Directors. (The Company's obligations under this Section 2B(a) shall be deemed
satisfied if two persons are elected to the Board by holders of Preferred Shares
pursuant to the Certificate of Designation).

       (b) If Shares representing at least 50% in the aggregate of the Initial
Interest cease to be beneficially owned by Permitted Owners, one of the two
Investor Nominees (as specified by the Permitted Owners) shall immediately
resign as a director upon the Company's written request. For as long as Shares
representing at least 25% in the aggregate of the Initial Interest are
beneficially owned by Permitted Owners, Permitted Owners shall continue to have
the right to designate one person who shall be the Company's nominee for
election to the Company's Board of Directors. The Company shall nominate the
person so designated and shall use reasonable efforts to have the nominee of the
Permitted Owners elected to its Board of Directors. (The Company's obligations
under this Section 2B(b) shall be deemed satisfied if one person is elected to
the Board by holders of Preferred Shares pursuant to the Certificate of
Designation).

       (c) If at any time Shares representing at least 25% in the aggregate of
the Initial Interest cease to be beneficially owned by Permitted Owners,
Permitted Owners shall cease to be entitled to designate any person for
nomination by the Company for election to its Board of Directors, and the
Investor Nominee currently serving as a director (or both Investor Nominees
currently serving as directors, as the case may be) shall immediately resign
upon the Company's written request.

       2C. REMOVAL AND REPLACEMENT.

       (a) If at any time Permitted Owners notify the Board of Directors of
their wish to remove any incumbent Investor Nominee as a director, the Board
shall vote to remove the Investor Nominee (if his or her removal is permitted
under the Company's by-laws and the Delaware General Corporation Law). Removal
of an incumbent Investor Nominee by the Board otherwise than at the request of
the Permitted Owners shall require their prior written consent unless the
removal is based upon the Investor Nominee's willful misconduct.

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       (b) If at any time a vacancy is created on Board of Directors by reason
of the incapacity, death, removal or resignation of an incumbent Investor
Nominee, the Permitted Owners shall designate a person to fill the vacancy (who
promptly shall be appointed by the incumbent directors). If the Permitted Owners
nominate an Investor Nominee for election to the Board of Directors and the
Company's stockholders fail to elect him or her to office, the Board of
Directors shall increase the number of directors on the Board of Directors by
one (if necessary to permit the appointment of a substitute Investor Nominee),
and the Investor and its Permitted Transferees shall be entitled to designate a
substitute Investor Nominee to fill the resulting vacancy. The incumbent
directors shall promptly appoint the substitute Investor Nominee as a director.

       (c) At each meeting of stockholders of the Company at which directors are
elected, the nominees for directors proposed by the Company shall include the
Investor Nominee or Nominees required pursuant to this Agreement.

       2D. INVESTOR NOMINEE.

       Each incumbent Investor Nominee shall receive notice of each meeting of
the Board of Directors at the same time and in the same manner as other members
of the Board. Each incumbent Investor Nominee shall be entitled to
indemnification rights, travel and expense reimbursement and compensation
substantially similar to those of other non-employee directors of the Company.
The Company shall at all times maintain a directors' and officer' insurance
policy covering each incumbent Investor Nominee that provides in the aggregate
substantially the same coverage as the policy covering the current directors of
the Company as of the date of this Agreement.

       2E. OBSERVER

       If under Section 2B the Permitted Owners are entitled to designate only
one person as the Company's nominee for election to its Board of Directors, the
following provisions shall apply:

           (1) if the Permitted Owners' designee was selected by the Bain
       Investors, the MDP Investors shall be entitled to designate one other
       person to attend meetings of the Company's Board of Directors as an
       observer (but not as a participant) for as long as Shares representing at
       least 25% in the aggregate of the MDP Investors' Initial Interest
       continue to be beneficially owned by the MDP Investors; and

           (2) if the Permitted Owners' designee was selected by the MDP
       Investors, the Bain Investors shall be entitled to designate one other
       person to attend meetings of the Company's Board of Directors as an
       observer (but not as a participant) for as long as Shares representing at
       least 25% in the aggregate of the Bain Investors' Initial Interest
       continue to be beneficially owned by the Bain Investors.

The observer designated by the MDP Investors or the Bain Investors, as the case
may be, shall receive notice of each meeting of the Board of Directors at the
same time and in the same manner as the members of the Board. The Company shall
have the right to approve the observer designated by the MDP Investors or the
Bain Investors, as the case may be, (but shall not unreasonably withhold or
delay its approval).

       2F. ACTIONS BY PERMITTED OWNERS.

       Any action by Permitted Owners under this Section 2 shall be by majority
vote of the Permitted Owners, with each Preferred Share having a number of votes
equal to the number of Converted Shares into which it may then be converted, and
each Converted Share having one vote.

       3. CERTAIN ACTIONS OF THE COMPANY.

                                      -75-
<PAGE>   4
       3A. ACTIONS. Subject to Section 3B, the Company shall not do any of the
following (whether in one or a series of related actions or transactions)
without the approval of holders of a majority of the Shares then beneficially
owned by Permitted Owners:

           (1) declare or pay any dividend or other payment to holders of Common
       Stock or any other securities junior in right of payment to the Preferred
       Shares;

           (2) increase the size of the Company's Board (other than pursuant to
       Sections 2A and 2C(b));

           (3) merge or consolidate with, or permit any Subsidiary to merge or
       consolidate with, any Person (other than a merger or consolidation
       between the Company and a wholly-owned Subsidiary or between one
       wholly-owned Subsidiary and another), or acquire, or permit any
       Subsidiary to acquire, any interest in any Person or business (whether by
       purchase of assets, purchase of stock, merger or otherwise), involving an
       aggregate consideration (including assumed liabilities) exceeding
       $20,000,000 in any one transaction or series of related transactions or
       exceeding $50,000,000 in any 12-month period;

           (4) divest or dispose of, or permit any Subsidiary to divest or
       dispose of, any business or other assets (other than obsolete or worn-out
       assets), whether by sale of assets, sale of stock, merger or otherwise,
       involving an aggregate consideration exceeding $20,000,000 in any one
       transaction or series of related transactions or exceeding $50,000,000 in
       any 12-month period;

           (5) become subject to or permit any Subsidiary to become subject to,
       or amend, any Contract which by its terms would restrict the Company's
       right to perform the provisions of this Agreement, the Registration
       Agreement, the Certificate of Designation, the Company's certificate of
       incorporation and the Company's bylaws that benefit the Investors;

           (6) enter into or amend, or permit any Subsidiary to enter into or
       amend, any Contract, transaction or arrangement with any of its or any
       Subsidiary's officers, directors, employees, stockholders or Affiliates,
       except for (i) customary employment and director arrangements consistent
       with past practice, (ii) benefit programs on reasonable terms consistent
       with past practice, (iii) transactions or arrangements between the
       Company and any wholly-owned Subsidiary or between one wholly-owned
       Subsidiary and another (treating 3CI Complete Compliance Corporation as a
       wholly-owned Subsidiary for purposes of this clause (iii)), and (iv)
       transactions with an Affiliate that arise solely as a result of owning an
       equity interest in the Affiliate; or

           (7) directly or indirectly, create, incur, issue, assume, guarantee
       or otherwise become directly or indirectly liable, contingently or
       otherwise, with respect to (collectively, "incur"), or permit any
       Subsidiary to incur, any Indebtedness (including Acquired Debt), and the
       Company shall not issue any Disqualified Stock and will not permit any
       Subsidiary to issue any shares of preferred stock; provided, however,
       that the Company may incur Indebtedness (including Acquired Debt) or
       issue Disqualified Stock, and the Company's Subsidiaries may incur
       Indebtedness or issue preferred stock, if the Fixed Charge Coverage Ratio
       for the Company's most recently ended four full fiscal quarters for which
       internal financial statements are available immediately preceding the
       date on which such additional Indebtedness is incurred or such
       Disqualified Stock or preferred stock is issued would have been at least
       1.75 to 1.0 in the case of any such incurrence or issuance occurring on
       or prior to the second anniversary of the date of Closing and 2.0 to 1.0
       in the case of any such incurrence or issuance that occurs thereafter, in
       each case determined on a pro forma basis (including a pro forma
       application of the net proceeds therefrom), as if the additional
       Indebtedness had been incurred or the preferred stock or Disqualified
       Stock had been issued, as the case may be, at the beginning of such
       four-quarter period.

                                      -76-
<PAGE>   5
Capitalized terms used in Section 3A(7) which are not defined elsewhere in this
Agreement have the same meanings that the same or corresponding terms are given
in the trust indenture to be entered into by the Company in connection with its
offering of the Subordinated Notes (the "Trust Indenture"). The restriction in
Section 3A(7) shall not prohibit the incurrence of any Permitted Debt (as
"Permitted Debt" is defined in connection with the corresponding covenant by the
Company under the Trust Indenture), but only to the extent that the actual
definitions in the Trust Indenture of "Permitted Debt" and the other capitalized
terms used in Section 3A(7) which are not defined elsewhere in this Agreement
are no more permissive or otherwise favorable to the Company than the
definitions used in the description of the Subordinated Notes that the Company
has provided to the Investors (being a draft prepared by Latham & Watkins dated
July 16, 1999, bearing the following footer on each page: NY_DOCS\356862[W97]).

       3B. TERMINATION. The restriction in Section 3A(1) shall terminate when
Permitted Owners cease beneficially to own Preferred Shares representing at
least 25% in the aggregate of the Initial Interest. The restriction in Section
3A(2) shall terminate when Permitted Owners cease to be entitled under both this
Agreement and the Certificate of Designation to nominate any person for election
to the Company's Board of Directors. The restrictions in each of Sections 3A(3),
(4), (5), (6) and (7) shall terminate when Permitted Owners cease beneficially
to own Shares representing at least 20% in the aggregate of the Initial
Interest.

       4. STANDSTILL AND RESTRICTIONS ON TRANSFER.

       4A. STANDSTILL. Unless previously agreed to in writing by the Company,
until the earliest to occur of (x) the date on which the Investors and Permitted
Transferees cease beneficially to own any Shares, (y) the Investors have
completed a distribution of all Shares to their partners, or (z) the first
anniversary of the date of this Agreement, Permitted Owners shall not: (i)
acquire any securities of the Company (other than upon conversion of Preferred
Shares) if, after the acquisition, they would beneficially own more than 30% of
the voting power of the Company's outstanding securities; or (ii) acquire, or
attempt to acquire, directly or indirectly, control of the Company (through a
proxy contest or otherwise) or any of the Company's businesses or assets,
except, in each case, (a) in response to a proposal that has been made to the
Company's stockholders that would materially and adversely affect the Investors
or their investment in the Company or the Shares or (b) pursuant to the exercise
of preemptive or purchase rights under the Purchase Agreement or the Certificate
of Designation.

       4B. RESTRICTIONS ON TRANSFER. Prior to the fifth anniversary of the date
of this Agreement, except for Transfers to a Permitted Transferee, no Permitted
Owner shall Transfer any Preferred Shares. This restriction shall not apply to
(i) the Transfer of any Preferred Shares which a Permitted Owner has a right to
have redeemed pursuant to Section 5A of the Certificate of Designation but which
for any reason the Company has failed to redeem within 30 days after the
Permitted Owner's exercise of his or its redemption right (ii) or to the
Transfer of any securities other than Preferred Shares. The right of a Permitted
Owner under the preceding sentence shall be in addition to any other rights and
remedies available to the Permitted Owner at law or in equity.

       5.  MISCELLANEOUS.

       5A. NOTICES. All Notices under this Agreement shall be in writing and
sent by certified or registered mail, overnight messenger service, telecopier or
personal delivery, as follows:

       (a) if to Stericycle, to:

                                            Stericycle, Inc.
                                            28161 North Keith Drive
                                            Lake Forest, Illinois 60045

                                      -77-
<PAGE>   6
                          Attention:   Mr. Mark C. Miller
                                       President and Chief Executive Officer
                          Telecopier:  (847) 367-9493

           with a required copy to:

                                       Johnson and Colmar
                                       300 South Wacker Drive
                                       Suite 1000
                                       Chicago, Illinois 60606
                                       Attention:  Craig P. Colmar, Esq.
                                       Telecopier: (312) 922-9283

(b) if to the Bain Investors, in care of:

                                       Bain Capital, Inc.
                                       Two Copley Place
                                       Boston, Massachusetts 02116
                                       Attention:  Mr. Stephen G. Pagliuca
                                                   Mr. Robert Gay
                                                   Mr. John P. Connaughton
                                                   Mr. Joe Pretlow
                                       Telecopier: (617) 572-3274

           with a required copy to:

                                       Kirkland & Ellis
                                       200 East Randolph Drive
                                       Chicago, Illinois 60601
                                       Attention:      Jeffrey C. Hammes, P.C.
                                       Telecopier:     (312) 861-2200

(c) if to the MDP Investors, in care of:

                                       Madison Dearborn Partners, Inc.
                                       Three First National Plaza
                                       Suite 3800
                                       Chicago, Illinois 60602
                                       Attention:  Mr. Thomas R. Reusche
                                       Telecopier: (312) 895-1001

           with a required copy to:

                                       Kirkland & Ellis
                                       200 East Randolph Drive
                                       Chicago, Illinois 60601
                                       Attention:   Michael H. Kerr, P.C.
                                       Telecopier:  (312) 861-2200

All Notices sent by certified or registered mail shall be considered to have
been given three business days after being deposited in the mail. All Notices
sent by overnight courier service, telecopier or personal delivery shall be
considered to have been given when actually received by the intended recipient.
A Party may change its address for purposes of this Agreement by Notice in
accordance with this Section 5A.

                                      -78-
<PAGE>   7
         5B. WAIVER. The rights and remedies of the Parties are cumulative and
not alternative. Neither the failure nor any delay by any Party in exercising
any right, power or privilege under this Agreement or the documents referred to
in this Agreement shall operate as a waiver of that right, power or privilege,
and no single or partial exercise of any right, power or privilege shall
preclude any other or further exercise of that right, power or privilege or the
exercise of any other right, power or privilege. All waivers shall be in writing
signed by the Party to be charged with the waiver, and no waiver that may be
given by a Party shall be applicable except in the specific instance for which
it is given.

         5C. ENTIRE AGREEMENT. This Agreement supersedes all prior agreements
between the Parties with respect to its subject matter (including the standstill
provision of any confidentiality agreement between the Parties) and constitutes
a complete and exclusive statement of the terms of the agreement between the
Parties with respect to its subject matter. This Agreement may not be amended
except by a written agreement signed by the Party to be charged with the
amendment.

         5D. NO THIRD PARTY BENEFICIARIES. Nothing in this Agreement shall be
considered to give any Person other than the Parties (and Permitted Transferees)
any legal or equitable right, claim or remedy under or in respect of this
Agreement or any provision of this Agreement. This Agreement and all of its
provisions are for the sole and exclusive benefit of the Parties and their
respective successors and permitted assigns.

         5E. EQUITABLE RELIEF. In addition to any other remedies which may be
available, the Company and each Permitted Owner shall be entitled to equitable
relief, including injunctive relief and specific performance, in the event of
any breach of the provisions of this Agreement, the Purchase Agreement, the
Registration Rights Agreement or the Certificate of Designation by another
Party, and neither the Company nor any Permitted Owner nor the Investor Nominee
or Nominees shall oppose the granting of such relief.

         5F. SEVERABILITY. If any provision of this Agreement is held invalid or
unenforceable by a court of competent jurisdiction, the other provisions of this
Agreement shall remain in full force and effect. Any provision of this Agreement
which is held invalid or unenforceable only in part shall remain in full force
and effect to the extent not held invalid or unenforceable.

         5G. CAPTIONS. The captions of sections of this Agreement are for
convenience only and shall not affect this the construction or interpretation of
this Agreement.

         5H. CONSTRUCTION. All references in this Agreement to "Section" or
"Sections" refer to the corresponding section or sections of this Agreement. All
words used in this Agreement shall be construed to be of the appropriate gender
or number as the context requires. Unless otherwise expressly provided, the word
"including" does not limit the preceding words or terms.

         5I. COUNTERPARTS. This Agreement may be executed in one or more
counterparts, each of which shall be considered an original copy of this
Agreement and all of which, when taken together, shall be considered to
constitute one and the same agreement.

         5J. GOVERNING LAW. This Agreement shall be governed by the Laws of the
State of Illinois without regard to conflicts of laws principles.

         5K. BINDING EFFECT. This Agreement shall apply to, be binding in all
respects upon and inure to the benefit of Parties and their respective
successors and permitted assigns.

                                      -79-
<PAGE>   8
       In witness, the Parties have executed this Agreement.

                              STERICYCLE, INC.

                              By:    /s/ Frank J.M. ten Brink
                                     ---------------------------------
                                       Name: Frank J.M. ten Brink
                                       Title: CFO

                              BAIN CAPITAL FUND VI, L.P.

                              By:    Bain Capital Partners VI, L.P.
                                     Its:  General Partner

                              By:    Bain Capital Investors VI, Inc.
                                     Its:  General Partner

                              By:    /s/ John P. Connaughton
                                     ---------------------------------
                                       A Managing Director

                              BCIP ASSOCIATES II

                              By:    Bain Capital, Inc.
                                     Its:  Managing Partner

                              By:    /s/ John P. Connaughton
                                     ---------------------------------
                                       A Managing Director

                              BCIP ASSOCIATES II-B

                              By:    Bain Capital, Inc.
                                     Its:  Managing Partner

                              By:    /s/ John P. Connaughton
                                     ---------------------------------
                                       A Managing Director

                              BCIP ASSOCIATES II-C

                              By:    Bain Capital, Inc.
                                     Its:  Managing Partner

                              By:    /s/ John P. Connaughton
                                     ---------------------------------
                                       A Managing Director

                              BCIP TRUST ASSOCIATES II

                              By:    Bain Capital, Inc.
                                     Its:  Managing Partner

                              By:    /s/ John P. Connaughton
                                     ----------------------------------------
                                       A Managing Director

                                      -80-
<PAGE>   9
                              BCIP TRUST ASSOCIATES II-B

                              By:    Bain Capital, Inc.
                                     Its:  Managing Partner

                              By:    /s/ John P. Connaughton
                                     ----------------------------------------
                                       A Managing Director

                              SANKATY HIGH YIELD ASSET PARTNERS, L.P.

                              By:    [signature illegible]
                                     ----------------------------------------
                                       A Managing Director

                              PEP INVESTMENTS PTY. LIMITED

                              By:    Bain Capital, Inc.
                                     Its:  Attorney-in-Fact

                              By:    /s/ John P. Connaughton
                                     ----------------------------------------
                                       A Managing Director

                              BROOKSIDE CAPITAL PARTNERS, L.P.

                              By:    /s/ Ed [last name illegible]
                                     ----------------------------------------
                                       A Managing Director

                              RANDOLPH STREET PARTNERS II

                              By:    [signature illegible]
                                     ----------------------------------------
                                       A General Partner

                                      -81-
<PAGE>   10
                              MADISON DEARBORN CAPITAL PARTNERS III, L.P.

                              By:    Madison Dearborn Partners III, L.P.
                                     Its:  General Partner

                              By:    Madison Dearborn Partners, LLC
                                     Its:  General Partner

                              By:    /s/ Thomas R. Reusche
                                     ----------------------------------------
                                       A Managing Director

                              MADISON DEARBORN SPECIAL EQUITY III, L.P.

                              By:    Madison Dearborn Partners III, L.P.
                                     Its:  General Partner

                              By:    Madison Dearborn Partners, LLC
                                     Its:  General Partner

                              By:    /s/ Thomas R. Reusche
                                     ----------------------------------------
                                       A Managing Director

                              SPECIAL ADVISORS FUND I, LLC

                              By:    Madison Dearborn Partners III, L.P.
                                     Its:  Manager

                              By:    Madison Dearborn Partners, LLC
                                     Its:  General Partner

                              By:    /s/ Thomas R. Reusche
                                     ----------------------------------------
                                       A Managing Director

                                      -82-
<PAGE>   11
                                   SCHEDULE I

                                    INVESTORS

<TABLE>
<CAPTION>
NAME AND ADDRESS                                    NUMBER OF SHARES PURCHASED            PURCHASE PRICE
<S>                                                 <C>                                 <C>
Bain Capital Fund VI, L.P.                               25,403.76                      $      25,403,759
c/o Bain Capital, Inc.
Two Copley Place
Boston, Massachusetts 02116

BCIP Associates II                                        4,491.38                      $        4,491,378
c/o Bain Capital, Inc.
Two Copley Place
Boston, Massachusetts 02116

BCIP Associates II-B                                        615.62                      $          615,619
c/o Bain Capital, Inc.
Two Copley Place
Boston, Massachusetts 02116

BCIP Associates II-C                                      1,319.76                      $        1,319,760
c/o Bain Capital, Inc.
Two Copley Place
Boston, Massachusetts 02116

BCIP Trust Associates II                                  1,291.22                      $        1,291,222
c/o Bain Capital, Inc.
Two Copley Place
Boston, Massachusetts 02116

BCIP Trust Associates II-B                                  206.08                      $          206,084
c/o Bain Capital, Inc.
Two Copley Place
Boston, Massachusetts 02116

Sankaty High Yield Asset Partners, L.P.                   1,856.25                      $        1,856,250
c/o Bain Capital, Inc.
Two Copley Place
Boston, Massachusetts 02116

PEP Investments Pty. Limited                                 84.68                      $           84,678
c/o Bain Capital, Inc.
Two Copley Place
Boston, Massachusetts 02116

Brookside Capital Partners, L.P.                          1,856.25                      $        1,856,250
c/o Bain Capital, Inc.
Two Copley Place
Boston, Massachusetts 02116

Randolph Street Partners II                                 375.00                      $          375,000
</TABLE>

                                      -83-
<PAGE>   12
<TABLE>
<S>                                                     <C>                             <C>
200 East Randolph Drive
Chicago, Illinois 60601

Madison Dearborn Capital Partners III, L.P.              36,538.68                      $       36,538,683
c/o Madison Dearborn Partners, Inc.
Three First National Plaza
Suite 3800
Chicago, Illinois 60602

Madison Dearborn Special Equity III, L.P.                   811.32                      $          811,317
c/o Madison Dearborn Partners, Inc.
Three First National Plaza
Suite 3800
Chicago, Illinois 60602

Special Advisors Fund I, LLC                                 150.0                      $          150,000
c/o Madison Dearborn Partners, Inc.
Three First National Plaza
Suite 3800
Chicago, Illinois 60602                                 ----------                      ------------------

                                                            75,000                      $       75,000,000
</TABLE>

                                      -84-

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