Document:

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                                                                       EX. 10.26

                           VENDOR CONTRACTS AGREEMENT

        THIS VENDOR CONTRACTS AGREEMENT, dated as of July 21, 1998, (this
"Agreement"), is made by and between THE ADVISORY BOARD COMPANY, a Maryland
corporation ("ABC") and THE CORPORATE EXECUTIVE BOARD COMPANY (formerly known as
the Corporate Advisory Board Company), a Delaware corporation ("CEB").

        WHEREAS, ABC and CEB are parties to a Vendor Contracts Agreement, dated
October 31, 1997 (the "Original Agreement");

        WHEREAS, ABC and CEB desire to amend and restate the Original Agreement,
among other things, to extend the term of the Original Agreement through October
31, 1998;

        WHEREAS, the parties hereto desire to amend, modify and restate the
Original Agreement in accordance with the foregoing; and

        WHEREAS, the parties hereto amend and restate the following recitals:

                                    RECITALS

        A.      ABC and CEB have entered into a Distribution Agreement dated as
of October 31, 1997 (the "Distribution Agreement"), providing for the
contribution by ABC of the Transferred Business to CEB.

        B.      Following the Contribution, subject to the conditions set forth
in the Distribution Agreement, all issued and outstanding shares of capital
stock of CEB were distributed to the Sole Stockholder.

        C.      In the interest of an orderly transition with respect to the
transfer of the Transferred Business to CEB and certain third-party vendor
contracts relating thereto (the "Vendor Contracts"), the parties desire to
provide for (i) the provision during the Transition Period of services pursuant
to the Vendor Contracts (the "Vendor Services") to CEB or ABC as appropriate and
(ii) the appropriate allocation of related costs and expenses relating to such
Vendor Services.

        The parties agree as follows:

        1.      Definitions. Unless the context otherwise requires, capitalized
terms not otherwise defined herein shall have the respective meanings given to
them in the Distribution Agreement.

        2.      Vendor Services.

        (a)     The Vendor Contracts are set forth in Attachment 1 hereto.
Subject to the terms of this Agreement, upon the written request setting forth
additional or amended Vendor Services to be provided to CEB made by an Executive
Vice President of CEB or a person designated to act on his behalf in an
instrument executed by such CEB Executive Vice President and

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<PAGE>   2

delivered to ABC, ABC shall provide, or cause provision, to CEB of each of the
Vendor Services with respect to the Transferred Business in the manner and to
the same general extent as such Vendor Services have been provided to ABC in
connection with the Transferred Business before the Contribution.

        (b)     Costs and expenses relating to Vendor Contracts shall be
allocated as shall be determined by the parties as follows or as otherwise shall
be mutually agreed in writing by the parties:

                (i)     Segregate Vendor Contract Invoices: If invoices relating
                to Vendor Services can be divided to reflect properly the Vendor
                Services provided to ABC and CEB, respectively, such invoices
                shall be segregated and paid directly by the appropriate party
                to whom the related Vendor Services were provided.

                (ii)    Reimburse ABC: In the event that invoices relating to
                Vendor Services cannot be segregated and paid as described in
                subparagraph (i) above, CEB shall pay its allocated share
                directly or reimburse ABC for Vendor Services provided to CEB
                pursuant to this Agreement as set forth in Attachment 1.

        3.      Term. Except with respect to Section 6, the term of this
Agreement shall be two (2) years commencing on October 31, 1997 (the "Term").
CEB shall have the right to terminate a Vendor Service or Vendor Services upon
sixty (60) days prior written notice to ABC. Termination of one or more Vendor
Services by CEB shall not affect the obligation of ABC to furnish all other
Services for the remainder of the Term.

        4.      Nondisclosure. In the event that, during the Term and in
connection with a party's performance of its obligations hereunder, either party
shall receive information concerning the other party hereto which the receiving
party knows, or has reason to believe, is confidential or proprietary to the
party to whom such information relates, the party receiving such information
shall take all reasonable steps to (a) protect and hold such information in
confidence and prevent its disclosure to third parties unless such third parties
are under a duty of confidentiality to the party to which such information
relates; and (b) restrict its use to those purposes consented to in writing by
the party to whom such information relates; provided, however, that the party
receiving such information shall not be required to protect or hold in
confidence any information or data which (i) is or becomes available to the
public without the fault of the receiving party, (ii) is independently developed
by the receiving party, (iii) is disclosed to the receiving party by a third
party known to the receiving party not to be under any duty of confidentiality
to the party to whom such information relates with respect to such information
or (iv) except as may otherwise be required by law. This Section 4 shall not
limit the obligation of the parties under the Distribution Agreement to provide
access to records after the date hereof.

        5.      Limitation on Liability. ABC's liability to CEB in connection
with this Agreement and the Vendor Services to be provided by ABC shall be
limited to actual damages arising from ABC's gross negligence or willful
misconduct in the performance of its duties and responsibilities hereunder;
provided, however, that, in no event shall ABC be liable for any incidental or
consequential damages.

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        6.      Indemnity.

        (a)     ABC agrees to defend, indemnify and hold CEB and its officers,
directors, employees and agents harmless from and against all liabilities,
losses, claims, damages and expenses of any nature, including reasonable
attorneys' fees, that are reasonably incurred by CEB arising out of the
performance of the Services hereunder, except where such liability, loss, claim,
damage or expense shall have been caused by CEB's gross negligence or willful
misconduct in the performance of its duties and responsibilities hereunder.

        (b)     CEB agrees to defend, indemnify and hold ABC and its officers,
directors, employees and agents harmless from and against all liabilities,
losses, claims, damages and expenses of any nature, including reasonable
attorneys' fees, that are reasonably incurred by ABC arising out of the
performance of the Services hereunder, except where such liability, loss, claim,
damage or expense shall have been caused by ABC's gross negligence or willful
misconduct in the performance of its duties and responsibilities hereunder.

        7.      Mutual Cooperation. ABC and CEB will provide each other with
information and assistance reasonably necessary to investigate, defend or
prosecute any claims, suits, charges, including but not limited to equal
employment opportunity, workers compensation, insurance and similar claims
brought by or against ABC or CEB relating to either of their businesses. This
provision shall survive termination of this Agreement.

        8.      Third Party Rights. Nothing in this Agreement, express or
implied, is intended to confer upon any person (including, without limitation,
employees), other than the parties hereto and their respective successors and
assigns, any rights or remedies of any nature whatsoever under or by reason of
this Agreement.

        9.      Relationship of Parties. Nothing in this Agreement shall be
deemed or construed by the parties or any third party as creating the
relationship of principal and agent, partnership or joint venture between the
parties, it being understood and agreed that no provision contained herein, and
no act of the parties, shall be deemed to create any relationship between the
parties other than the relationship of independent contractor nor be deemed to
vest any rights, interest or claims in any third parties.

        10.     Successor and Assigns. This Agreement shall inure to the benefit
of and be binding upon the respective successors and assigns of the parties
hereto, provided that this Agreement may not be assigned by either of the
parties hereto without the prior written consent of the other.

        11.     Notices. All notices and other communications required or
permitted to be given under this Agreement shall be in writing and shall be
deemed to have been duly given if delivered by hand or mailed, postage prepaid
or by certified or registered mail, and addressed to the applicable party at the
respective addresses set forth in the Distribution Agreement (or at such other
address for a party as shall be specified by a like notice).

        12.     Governing Law. The validity, enforceability and performance of
this Agreement shall be governed by and construed in accordance with the laws of
the State of Maryland (excluding its choice of law rules).

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        13.     Entire Agreement. The parties intend that the terms of this
Agreement, including the attached schedules, shall be the final expression of
their agreement with respect to the subject matter hereof and may not be
contradicted by evidence of any prior or contemporaneous agreement. The parties
further intend that this Agreement shall constitute the complete and exclusive
statement of its terms and that no extrinsic evidence whatsoever may be
introduced in any judicial, administrative or other legal proceedings involving
this Agreement.

        14.     Counterparts. This Agreement may be executed in counterparts,
each of which shall be deemed an original, but all of which taken together shall
constitute one and the same instrument.

        15.     Headings. The headings used in this Agreement are inserted for
convenience of reference only and shall not affect the meaning or interpretation
of any provision of this Agreement.

        16.     Amendments and Waivers. This Agreement may not be amended except
upon the written consent of all of the parties. By an instrument in writing, any
party may waive compliance by any other party with any term or provision of this
Agreement that such other party was or is obligated to comply with or perform,
provided, however, that such waiver shall not operate as a waiver of, or
estoppel with respect to, any other or subsequent failure. No failure to
exercise and no delay in exercising any right, remedy, or power hereunder shall
operate as a waiver thereof, nor shall any single or partial exercise of any
right, remedy, or power hereunder preclude any other or further exercise thereof
or the exercise of any other right remedy, or power provided herein or by law or
in equity. The waiver by any party of the time for performance of any act or
condition hereunder does not constitute a waiver of the act or condition itself.

        17.     Expenses. Whether or not the transactions contemplated in this
Agreement are consummated, unless specifically provided otherwise in this
Agreement (including all Schedules hereto), each party shall bear and pay all
expenses incurred by it or on its behalf in connection with the preparation of
this Agreement and consummation of the transactions described herein.

        18.     Severability. If any provision of this Agreement, or the
application thereof to any person, place or circumstance, shall be held by a
court of competent jurisdiction to be void, invalid or unenforceable, the
remainder of this Agreement and such provisions as applied to other persons,
places or circumstances shall remain in full force and effect.

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<PAGE>   5

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

                                            THE ADVISORY BOARD COMPANY,
                                            a Maryland corporation

                                            By:
                                               ---------------------------------

                                            Its:
                                                --------------------------------

                                            THE CORPORATE EXECUTIVE BOARD
                                            COMPANY, a Delaware corporation

                                            By:
                                               ---------------------------------

                                            Its:
                                                --------------------------------

                                       5<PAGE>   1

                                                                   EXHIBIT 10.27

                               SUBLEASE AGREEMENT

        THIS SUBLEASE, dated as of July 21, 1998, by and between THE ADVISORY
BOARD COMPANY, a Maryland corporation (hereinafter called "Sublessor"), and THE
CORPORATE EXECUTIVE BOARD COMPANY (formerly known as The Corporate Advisory
Board Company), a Delaware corporation (hereinafter called "Sublessee").

        WHEREAS, ABC and CEB are parties to a Sublease Agreement, dated October
31, 1997 (the "Original Agreement");

        WHEREAS, ABC and CEB desire to amend and restate the Original Agreement,
among other things, to extend the time period required for prior written notice
to terminate this Sublease from five days to six months;

        WHEREAS, the parties hereto desire to amend, modify and restate the
Original Agreement in accordance with the foregoing; and

        WHEREAS, the parties hereto amend and restate the following recitals:

                                    RECITALS

        1.      John Hancock Mutual Life Insurance Company, a Massachusetts
corporation ("Lessor"), and Sublessor, as lessee, are the parties to a certain
Lease Agreement dated as of August 7, 1992 (the "Overlease"), pursuant to which
Lessor has leased to Sublessor the Premises (as hereinafter defined).

        2.      Sublessor and Sublessee have agreed that Sublessor will sublease
to Sublessee the Premises.

        3.      The parties desire to set out in detail their agreements and the
consideration for this Sublease.

                                    ARTICLE I
                                   DEFINITIONS

       As used herein, the following terms shall have the following meanings:

        1.1.    "Commencement Date" shall mean the date hereof.

        1.2.    "Sublease" shall mean this sublease agreement as amended from
time to time pursuant to the terms hereof.

        1.3.    "Sublease Term" shall mean the duration of the leasehold estate
created by this Sublease as specified in Article III hereof.

        1.4.    "Premises" shall mean and refer to the portion of the Overlease
Premises described in Attachment A hereto.

        1.5.    "Overlease Premises" shall mean the premises at 600 New
Hampshire Avenue, N.W., Washington, D.C., described in the Overlease.

        1.6.    "Termination Date" shall mean the date that is the end of the
Term as defined in the Overlease.

                                   ARTICLE II
                                DEMISED PROPERTY
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        2.1.    Sublease. Sublessor hereby subleases to Sublessee and Sublessee
hereby subleases from Sublessor the Premises.

                                   ARTICLE III
                                      TERM

        3.1.    Term. The term of this Sublease shall begin on the Commencement
Date and, unless earlier terminated as provided herein, shall end on the
Termination Date.

        3.2.    Termination. Each of Sublessee and Sublessor shall have the
right, in its absolute discretion and without liability to the other party, to
terminate this Sublease at any time during the Sublease Term on not less than
six (6) months prior written notice.

                                   ARTICLE IV
                                      RENT

        4.1.    Rent. During the term of this Sublease, Sublessee shall pay rent
to Sublessor in such annual amount per square foot of Premises as is equal to
the annual per square foot rent payable under the Overlease for the Overlease
Premises. Such rent payments shall be made in lawful money of the United States
of America, at Sublessor's address for notice hereunder or otherwise as
Sublessor may designate. Such rent shall be payable in equal monthly
installments on the first day of every calendar month during the term of this
Sublease.

        4.2     Annual Adjustments to Rent. To the extent that annual cost of
living adjustments increase the Annual Base Rent (as defined in the Overlease)
payable by Sublessor pursuant to the Overlease, an amount equal to such increase
shall be added to the rent payable under this Sublease pursuant to Section 4.1.

        4.3     Additional Rent for Operating Expenses. To the extent that
Additional Rent (as defined in the Overlease) relating to increased Operating
Expenses (as defined in the Overlease) is payable by Sublessor pursuant to the
Overlease, an amount equal to the portion of such Additional Rent that is in
proportion to the area of the Overlease Premises that is represented by the area
of the Premises shall be added to the rent payable under this Sublease pursuant
to Section 4.1.

        4.4     Additional Space; Amended Allocation. Sublessor and Sublessee
may, by mutual agreement, revise Attachment A to (i) add additional space to the
Premises to be leased by Sublessor under this Sublease, (ii) revise the location
of the space leased under this Sublease, or (iii) make such other modifications
and amendments as the parties may mutually agree.

                                    ARTICLE V
                                 USE OF PREMISES

        5.1.    Use of Premises. Sublessee shall use the Premises only for the
purpose of general office use and as otherwise described in the Overlease.

                                   ARTICLE VI
                            ASSIGNMENT AND SUBLETTING

        6.1.    Assignment and Sublease. Sublessee shall not mortgage, encumber,
assign, sublease or otherwise dispose of or transfer its interest in this
Sublease or the Premises except as may be permitted by the Overlease.

                                   ARTICLE VII
                             UTILITIES AND SERVICES
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        7.1.    Utilities and Services. Sublessor shall supply to the Premises
utilities and services to the extent that such utilities and services are
provided to Sublessor pursuant to the Overlease.

                                  ARTICLE VIII
                                 QUIET ENJOYMENT

        8.1.    Quiet Enjoyment. If Sublessee pays the rent and other charges
herein provided and performs all of the covenants and agreements herein
stipulated to be performed on Sublessee's part, Sublessee shall, at all times
during said term, peaceably and quietly have, hold and enjoy the Premises
without disturbance from Sublessor or anyone claiming by or through Sublessor,
subject to the terms of this Sublease and to the rights of the parties presently
or hereinafter secured by any deed of trust or mortgage against the Premises.

                                   ARTICLE IX
                             FIRE AND OTHER CASUALTY

        9.1.    Restoration of Damaged Premises. In the event the Premises are
damaged or destroyed or rendered partially untenantable for their then use by
fire or other casualty, the Sublessee shall notify Sublessor and promptly repair
the Premises and restore the same to the condition in which they were
immediately prior to the happening of such casualty.

        9.2.    Rent Abatement. During the period from the date of such casualty
until the Premises are repaired and restored, Sublessee's obligation to pay the
rent due hereunder, shall abate, but only to the extent that Sublessor's rent
payment obligations under the Overlease are abated. The abatement shall be in
the proportion of which the area of the Premises destroyed or rendered
untenantable bears to the total area of the Premises.

        9.3.    Fire and Other Casualty. Except as herein expressly provided,
this Sublease shall not terminate nor shall there be any abatement of rent as a
result of fire or other casualty.

                                    ARTICLE X
                                    INSURANCE

        10.1.   Casualty Insurance. The Sublessee shall maintain in effect
policies of (i) comprehensive liability insurance and (ii) insurance covering
Sublessee's furniture, furnishings, trade fixtures and all other personal
property from time to time on or in the Premises in an amount not less than 100%
of their actual replacement cost.

                                   ARTICLE XI
                              SURRENDER OF PREMISES

        11.1.   Surrender of Premises. The Sublessee shall on the expiration or
the sooner termination of the Sublease Term surrender to the Sublessor the
Premises, including all buildings, replacements, changes, additions, and
improvements constructed or placed by the Sublessee thereon, with all equipment
in or appurtenant thereto, and all movable trade fixtures installed by the
Sublessee.

                                   ARTICLE XII
                                  CERTIFICATES

        12.1.   Certificates. Either party shall, without charge, at any time
and from time to time hereafter, within ten (10) days after written request of
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the other, certify by written instrument duly executed and acknowledged to any
mortgagee or purchaser, or proposed mortgagee or proposed purchaser, or any
other person specified in such request: (a) as to whether this Sublease has been
supplemented or amended, and if so, the substance and manner of such supplement
or amendment; (b) as to the validity and force and effect of this Sublease, in
accordance with its tenor as then constituted; (c) as to the existence of any
default thereunder; (d) as to the existence of any offsets, counterclaims, or
defense thereto on the part of such other party; (e) as to the commencement and
expiration dates of the term of this Sublease; and (f) as to any other matters
as may reasonably be so requested. Any such certificate many be relied upon by
the party requesting it and any other person to whom the same may be exhibited
or delivered and the contents of such certificate shall be binding on the party
executing same.

                                  ARTICLE XIII
                           EVENTS OF DEFAULT, REMEDIES

        13.1.   Default. Any of the following occurrences, conditions, or acts
shall constitute an "Event of Default" under this Sublease:

        13.1.1.         If:

        (a) Sublessee defaults in making payment when due of any the rent, and
if such default shall continue for five (5) business days after Sublessor shall
have given written notice to Sublessee specifying such default and demanding
that same be cured;

        (b) Sublessee defaults in the observance or performance of any other
provisions of this Sublease, and such default continues for thirty (30) calendar
days after Sublessor shall have given written notice to Sublessee specifying
such default and demanding that the same be cured (unless such default cannot be
cured by the payment of money and cannot with due diligence be wholly cured
within such period of thirty (30) calendar days, in which case Sublessee shall
have such longer period as shall be necessary to cure the default, so long as
Sublessee proceeds diligently to attempt to cure the same within such thirty
(30) day period, prosecutes the cure to completion with due diligence, and
advises Sublessor from time to time, upon Sublessor's request, of the actions
which Sublessee is taking and the progress being made);

        13.1.2.         Sublessee abandons or vacates the Premises for a period
of ten (10) consecutive calendar days;

        13.1.3.         Sublessee files a petition in bankruptcy, for
reorganization or for an arrangement pursuant to Federal Bankruptcy law or any
similar federal or state law; is adjudicated bankrupt or become insolvent; is
unable to meet Sublessee's obligations as they become due; or takes any
corporate action in furtherance of any of the foregoing;

        13.1.4.         A petition or answer shall be filed proposing (a) the
adjudication of Sublessee as bankrupt or (b) the reorganization of Sublessee
pursuant to Federal Bankruptcy law or any similar federal or state law, and (i)
Sublessee shall consent to the filing thereof, or (ii) such petition or answer
shall not be discharged or denied within sixty (60) days after the filing
thereof;

        13.1.5.         A receiver, trustee, or liquidator (or other similar
official) of Sublessee shall be appointed with respect to (a) all or
substantially all of its businesses or assets or (b) the estate or interest of
Sublessee in the Premises and (i) shall not be discharged within sixty (60) days
thereafter or (ii) Sublessee consents to or acquiesces in such appointment;

        13.1.6.         The estate or interest of Sublessee in the Premises
shall
<PAGE>   5
be levied upon or attached in any proceeding and such process shall not be
vacated or discharged within sixty (60) days after such levy or attachment; or

        13.1.7.         Sublessee is dissolved, merged, consolidated or
reorganized, or any change occurs in the ownership or control of Sublessee,
without the prior written consent of Sublessor.

        13.1.8.         Notwithstanding the provisions of paragraphs 13.1.3,
13.1.4, 13.1.5 or 13.1.6 hereof, if at any time during the term hereof, (a)
proceedings in bankruptcy, insolvency or other similar proceedings are
instituted by or against Sublessee, whether or not such proceedings result in an
adjudication against Sublessee, or (b) should a receiver of the business or
assets of Sublessee be appointed; such proceedings or adjudications shall not
affect the validity of this lease so long as (i) the rent reserved hereunder
continues to be paid to Sublessor and (ii) the other terms, covenants and
conditions of this Sublease on the part of the Sublessee to be performed, are
performed. In such event, this Sublease shall continue to remain in full force
and in accordance with the terms herein contained.

        13.2.   Remedies. In case of Default,

        (a) the rent shall become due thereupon and be paid up to the time of
re-entry, expiration and/or dispossession;

        (b) Sublessor may elect the premises or any part or parts thereof,
whether in the name of Sublessor or otherwise, for a term or terms which may, at
Sublessor's option, be less than or exceed the period which would otherwise have
constituted the balance of the term of this sublease;

        (c) Sublessee shall also pay to Sublessor, as liquidated damages for the
failure of Sublessee to observe and perform Sublessee's covenants herein
contained, any deficiency between the (i) rent hereby reserved and (ii) the net
amount, if any, of the rents collected on account of the lease or leases of the
Premises for the period which would have constituted the balance of the Sublease
Term (hereinafter called "Liquidated Damages"). Liquidated Damages shall be paid
as the said rent shall become due and payable in monthly installments. Sublessee
shall also pay to Sublessor such reasonable expenses as Sublessor-may incur in
connection with reletting, such as brokerage and preparation for reletting
(hereinafter called "Consequential Damages").

        (d) Liquidated and Consequential Damages shall be paid in monthly
installments by Sublessee on the Rent Payment Dates specified in this Sublease.
Any suit brought to collect Liquidated and Consequential Damages for any month
shall not prejudice in any way the rights of Sublessor to collect Liquidated and
Consequential Damages for any subsequent month by a similar proceeding.
Sublessor, at Sublessor's option, may make such alterations, repairs,
replacements, and/or decorations in the premises as Sublessor; in Sublessor's'
sole judgment, considers advisable and necessary for the purpose of reletting
the premises; and the making of such alterations, repairs, replacements, and/or
decorations shall not operate or be construed to release Sublessee from
liability hereunder as aforesaid. Sublessor agrees to use its best efforts to
mitigate all damages and to elect the Premises in the event of any Default
specified herein.

                                   ARTICLE XIV
                             RIGHT TO CURE DEFAULTS

        14.1.   Default by Lessor. If Sublessor fails to perform any covenant or
agreement in this Sublease contained on the part of Sublessor to be performed,
then and in such event, after the continuance of any such failure or default for
thirty (30) calendar days after notice is given by Sublessee to Sublessor
(notwithstanding any delay or forbearance in giving
<PAGE>   6
such notice), Sublessee may cure such default. Sublessee may further make all
necessary payments in connection therewith, including, but not limited to the
payment of any reasonable attorney's fees, costs, and charges of or in
connection with any legal action which may have been brought. Sublessor agrees
to pay to Sublessee forthwith any amount so paid by the Sublessee, together with
interest thereon at the maximum legal rate, or if no such rate is established at
the rate of 12% per annum. All sums charged to Sublessor by Sublessee hereunder
shall be indebtedness of Sublessor to Sublessee payable on demand. If all such
indebtedness of Sublessor is not fully paid within 30 days after demand,
Sublessee may elect (i) to deduct such amount from rent subsequently becoming
due hereunder, (ii) terminate this Sublease upon thirty (30) calendar days
notice to Sublessor (unless Sublessor shall cure such default) or (iii) extend
this Sublease the same covenants and conditions and herein provided until such
indebtedness is fully paid by application to rents.

        14.2.   Default by Lessee. If Sublessee shall fail to-make or perform
any payment or act required by this Sublease, then Sublessor may (but need not),
make such payment or perform such act for the account of Sublessee. All amounts
so paid by Sublessor, and all incidental costs and expenses (including
attorneys' fees) incurred in connection with such payment or performance,
together with interest thereon at the maximum legal rate, or if no such rate is
established at the rate 12% per annum from the date of the making of such
payment or of the incurring of such costs and expenses, shall be paid by
Sublessee to Sublessor on demand.

                                   ARTICLE XV
                                  MISCELLANEOUS

        15.1.   Notices. All notices, demands, requests, consents, approvals,
offers, statements, and other instruments or communications required or
permitted to be given hereunder shall be in writing and shall be deemed to have
been given when delivered, or when mailed by first class registered or certified
mail, postage prepaid, and addressed as follows:

                If to Sublessor:

                David G. Bradley
                The Advisory Board Company
                600 New Hampshire Avenue, NW
                Washington, D.C.  20037

                If to Sublessee:

                Clay M. Whitson
                The Corporate Advisory Board Company
                600 New Hampshire Avenue, NW
                Washington, D.C.  20037

        15.2.   Amendments: Entire Agreement. This Sublease may not be amended,
modified, or terminated, nor may any obligation hereunder be waived orally, and
no such amendment, modification, termination, or waiver shall be effective for
any purpose unless it is in writing, signed by the party against whom
enforcement thereof is sought. This Sublease is intended by the parties to be an
entire, complete and integrated statement of all their respective rights,
obligations and remedies with respect to the subject matter of this Sublease.
All prior and contemporaneous oral or written statements, representations,
warranties or agreements are superseded and merged in this Sublease.

        15.3.   Severability. If any provisions of this Sublease or any
application thereof shall be invalid or unenforceable, the remainder of this
Sublease and any other application of such provision shall not be affected
thereby.
<PAGE>   7
        15.4.   Binding Effect. This Sublease shall be binding upon and inure to
the benefit of and be enforceable by the respective successors and assigns of
the parties hereto.

        15.5.   Captions. The table of contents, the Article headings, and the
Section headings are for convenience of reference only and shall not limit or
otherwise affect the meaning hereof.

        15.6.   Counterparts. This Sublease may be executed in counterparts,
each of which shall constitute an original and all of which shall be one and the
same document.

        15.7.   Governing Law. This Sublease shall be governed by and construed
in accordance with the laws of the District of Columbia.

        15.8.   Relationship of Parties. Sublessor and Sublessee shall not be
considered or deemed to be joint venturers or partners and neither shall have
the power to bind or obligate the other except as set forth herein.

        15.9.   Default of Lessor's Trustee. In the event the Sublessor is
involved in any bankruptcy or insolvency proceedings and the Sublessor or the
Sublessor's trustee or receiver fails to perform any of the Sublessor's
obligations under this Sublease with the result that Sublessee is unable to use
the Premises for Sublessee's intended use, Sublessee shall have the option to
terminate this Sublease.

        15.10.  Construction. All terms used in this Sublease, regardless of the
number or gender in which they are used, shall be deemed and construed to
include any other number, singular or plural, and any other gender, masculine,
feminine, neuter, as the context or sense of this Sublease or any section,
subsection, or clause herein may require as if such terms had been fully and
properly written in such number or gender.

        15.11.  Subordination to Overlease.  This Sublease is and shall remain
subject to the terms of the Overlease.

        15.12.  Exculpation. Nothing herein shall be construed to impose any
liability on the officers, directors or shareholders of Sublessee and
Sublessor's sole recourse under this Sublease (absent fraud or willful
misconduct by such officers, directors or shareholders) shall be against
Sublessee and the assets of Sublessee.

        IN WITNESS WHEREOF, the parties have caused this Sublease to be executed
by their respective duly authorized officers as of the 21st day of July, 1998.

                                  THE ADVISORY BOARD COMPANY, SUBLESSOR

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

                                  THE CORPORATE EXECUTIVE BOARD COMPANY, LESSEE

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

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