Document:

<PAGE>   1
                                                                       EX. 10.28

                                LICENSE AGREEMENT

        This License Agreement ("Agreement"), made as of January 19, 1999 and
effective as of October 31, 1997 (the "Effective Date"), by and between The
Advisory Board Company, a Maryland corporation (the "Advisory Board"), and The
Corporate Executive Board Company, a Delaware corporation (the "Company"),

                                   WITNESSETH:

        WHEREAS, prior to October 31, 1997, the Company was operated as a
division of the Advisory Board, and on October 31, 1997, all of the outstanding
shares of capital stock of the Company were distributed to David G. Bradley, the
sole stockholder of the Advisory Board;

        WHEREAS, the Advisory Board owns certain intellectual property which the
Company wishes to use for internal purposes in conducting its business in the
ordinary course; and

        WHEREAS, the Company desires to obtain a license from the Advisory Board
for such purposes, and the Advisory Board is willing to grant the Company such a
license, on the terms and conditions set forth below;

        NOW, THEREFORE, in consideration of the premises and mutual promises and
covenants hereinafter set forth, the parties hereto agree as follows:

                                    SECTION 1
                                   Definitions

The following capitalized terms used in this Agreement shall have the following
meanings:

        1.1     "Materials" shall mean the Public Materials and the Non-Public
                Materials.

        1.2     "Non-Public Materials" shall mean, collectively, the following
materials, whether in written or other formats or media, to the extent that the
copyright therein is owned by the Advisory Board:

(a)             Materials intended for use in the orientation and professional
                training of employees, including without limitation, course
                outlines, syllabi, "hand-outs" and videotaped presentations;

(b)             Materials describing Advisory Board employment policies and
                practices and employee directives and guidelines, including
                without limitation employee handbooks;

(c)             Certain computer software, as more specifically described in
                Annex A hereto;

(d)             Forms prepared for use by Advisory Board employees in connection
                with various administrative functions, including without
                limitation, the interviewing of

<PAGE>   2

                applicants, the evaluation of other employees, and the
                reimbursement of travel expenses; and

(e)             Any other materials which are used by the Advisory Board in
                performing internal administrative functions, copies of which
                have been provided to the Company;

provided, however, that the Non-Public Materials shall not include any materials
the content of which is specific to the health care industry.

1.3     "Public Materials" shall mean, collectively, the following materials,
whether in written or other formats or media, to the extent that copyright
therein is owned by the Advisory Board:

(a)             Materials prepared for use in marketing and promoting the
                Company's products and services;

(b)             The graphic design and lay-out of the Web page of the Advisory
                Board;

(c)             The graphic design and lay-out of the advertisements placed by
                the Advisory Board for the purpose of recruiting new employees;

(d)             The templates for written correspondence used by the Advisory
                Board in communicating with (i) current and past members, (ii)
                prospective members, and (iii) vendors; and

(e)             Any similar materials, copies of which have been provided to the
                Company;

provided, however, that the Public Materials shall not include any materials the
content of which is specific to the health care industry.

1.4     "Derivative Work" shall mean any work based on one or more of the
Materials, as defined in Section 1. A Derivative Work consists of any
modification wherein a Material is recast, transformed, or adapted, if the
changes in the Material, as a whole, represents an original work of authorship.

                                    SECTION 2
                                  License Grant

        2.1     Subject to the terms and conditions hereof, the Advisory Board
hereby grants to the Company a perpetual, royalty-free, non-exclusive, worldwide
license (without right to sublicense) (i) to use and make reproductions of the
Non-Public Materials, and Derivative Works thereof, solely for the purposes of
orienting and training Company employees and performing internal administrative
functions of the Company, and (ii) to use and make reproductions of the Public
Materials, and Derivative Works thereof, solely for the purpose of advertising,
marketing and promoting the Company's products and services, recruiting new
employees, and communicating with the Company's current, past and prospective
members, vendors, and applicants.

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        2.2     The Company agrees to include the following Copyright Notice on
Public Materials to the extent that copyright therein is owned by the Advisory
Board:

                (C)Copyright [year date] by The Advisory Board Company. All
                rights reserved. Use of The Advisory Board Company's copyrighted
                work in this [publication] appears with their permission.

        2.3     The Company agrees not to grant to any third party any license
to use any of the Materials or any Derivative Works of the Materials for any
purpose whatsoever.

                                    SECTION 3
               Ownership and Enforcement of Intellectual Property

        3.1     Subject to the rights granted under Section 2, the Advisory
Board shall retain all rights and title to and interest in the Materials,
including without limitation all proprietary rights and copyrights therein, and
the Company agrees not to dispute the Advisory Board's ownership thereof.

        3.2     All rights, title and interest in all Derivative Works of the
Materials, including without limitation all proprietary rights and copyrights
therein, which the Company may create during the term of this Agreement shall be
the sole and exclusive property of the Advisory Board. The Company agrees to
assign, and upon creation of each Derivative Work, automatically assigns, to the
Advisory Board ownership of all copyrights in each and every Derivative Work.
From time to time, upon the Advisory Board's request, the Company and/or its
authorized personnel shall confirm such assignment by execution and delivery of
such assignments or other written instruments as the Advisory Board may request.

        3.3     The Advisory Board, in its sole discretion, shall have the
exclusive right to file for, obtain and maintain copyright, patent, and/or other
forms of intellectual property protection for the Materials and Derivative Works
anywhere in the world, at its own expense.

        3.4     The Company shall promptly notify the Advisory Board of any
infringement or suspected infringement by a third party on the Advisory Board's
rights or title to or interest in the Materials or any Derivative Works of the
Materials of which the Company has knowledge. The Advisory Board shall have the
exclusive right (but not the obligation) to pursue at its own expense any and
all injunctive, compensatory and other remedies and relief against such third
party, and all such proceedings shall be exclusively under the direction and
control of the Advisory Board.

                                    SECTION 4
                          Representation and Warranties

        4.1     Each party hereby represents and warrants to the other party
that it has full power and authority to execute and deliver this Agreement and
to perform its obligations hereunder, and that the execution, delivery and
performance of this Agreement will not contravene, result in any breach of, or
constitute a default under, any order, judgment, decree or award of any court or

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<PAGE>   4

other governmental body to which it is subject, or any agreement or instrument
by which it is bound.

        4.2     The Advisory Board represents and warrants that (i) it is the
owner of all Materials, including without limitation all proprietary rights and
copyrights therein, licensed under this Agreement; (ii) it has the right to
licenses the Materials pursuant to this Agreement; and (iii) none of the
Materials infringe any intellectual property rights, including but not limited
to copyrights, of any third party, nor has any claim of such infringement been
threatened or asserted, nor is such a claim pending, against the Advisory Board.

        4.3     EXCEPT AS SET FORTH IN SECTIONS 4.1 AND 4.2, THE ADVISORY BOARD
HEREBY DISCLAIMS ANY AND ALL WARRANTIES, WHETHER WRITTEN OR ORAL, OR EXPRESS OR
IMPLIED, WITH RESPECT TO THE MATERIALS, INCLUDING WITHOUT LIMITATION ANY
WARRANTY OF QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR A PARTICULAR
USE OR PURPOSE.

                                    SECTION 5
                                 Confidentiality

        5.1     The Company acknowledges that the Non-Public Materials are
confidential, proprietary information of the Advisory Board, and agrees not to
disclose any of them to any third party without the prior written permission of
the Advisory Board, unless such information (i) becomes publicly available
through no act of the Company, or (ii) is disclosed in accordance with the
requirements of law, any regulation or regulatory body or any judgment, order or
requirement of any court or other competent authority. Further, the Company
agrees to exercise the same degree of care in safeguarding the confidentiality
of the Non-Public Materials as it exercises with respect to its own confidential
information, but in any event not less than reasonable care.

        5.2     In furtherance of its obligations pursuant to Section 5.1, the
Company agrees not to disclose any Non-Public Materials to any employee of the
Company other than those who have been informed of Licensee's confidentiality
obligations with respect thereto.

        5.3     The obligations of the Company under this Section 5 shall
survive termination or expiration of this Agreement.

                                    SECTION 6
                                 Indemnification

        6.1     The Company agrees to indemnify and hold harmless the Advisory
Board and its officers, directors, employees and agents, from and against all
threatened or pending claims, demands, causes of action, losses, damages,
penalties, fines, expenses and judgments, including, without limitation,
reasonable attorneys' fees and legal costs, incurred or suffered by any of them,
that arise out of a breach by the Company of this Agreement.

        6.2     The Advisory Board shall notify the Company promptly of any
claim for which the Advisory Board intends to seek indemnification pursuant to
Section 6.1. The Company shall have the exclusive right to control the defense
of any such claim, including the right to select

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counsel, and to settle any such claim; provided, however, that the Company shall
not settle any such claim against the Advisory Board to the extent such claim
will result in the Advisory Board's becoming subject to injunctive or other
equitable relief or otherwise adversely affecting the business of the Advisory
Board in any manner, without the prior written consent of the Advisory Board,
which consent shall not be unreasonably withheld, delayed or denied. At the
request of the Company, the Advisory Board shall cooperate in the defense of any
such action, at the expense of the Company.

                                    SECTION 7
                              Term and Termination

        7.1     This Agreement shall take effect as of the Effective Date first
above written and shall remain in effect through the third anniversary thereof.

        7.2     This Agreement shall be subject to termination by the Advisory
Board in the event of a material breach hereof by the Company, which breach is
not cured within thirty (30) days following notice thereof.

        7.3     The termination or expiration of this Agreement shall be without
prejudice to any rights or obligations of the parties that may have accrued
prior to such termination or expiration. The rights and obligations of the
parties under Sections 3, 5, 6, 7.3, 8.1, 8.2, 8.5, 8.10 and 8.11 shall survive
the expiration and termination hereof.

                                    SECTION 8
                                  Miscellaneous

        8.1     All notices, requests, demands and other communications which
are required or may be given pursuant to the terms of this Agreement shall be in
writing and shall be deemed given as of the date personally delivered, or five
(5) days after posting when mailed by registered or certified airmail, postage
prepaid, and addressed to the address of the recipient party written below, or
to such other address as may hereafter be communicated to the other party in
accordance with this Section 8.1, or twenty-four (24) hours after dispatch if
sent by facsimile during business hours of the receiving party to the facsimile
number indicated below, or to such other facsimile number as may hereafter be
communicated to the other party in accordance with this Section 8.1:

                (a)    If to the Advisory Board:

                       The Advisory Board Company
                       Attn.:  Jeffrey D. Zients
                       600 New Hampshire Avenue, N.W.
                       Washington, D.C.  20037
                       Facsimile:  (202) 339-6570

                (b)    If to the Company:

                       The Corporate Executive Board
                       Attn.:  James J. McGonigle
                       600 New Hampshire Avenue, N.W.

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<PAGE>   6

                       Washington, D.C.  20037
                       Facsimile:  (202) 672-5695

        8.2     No waiver of any provision of this Agreement shall be effective
as against the waiving party unless such waiver is in writing signed by the
waiving party. Waiver by a party in respect of specific matter shall not be
construed as or constitute either a continuing waiver or a waiver of any other
matter.

        8.3     This Agreement may be modified, supplemented or amended only by
a written instrument executed by the parties hereto.

        8.4     This Agreement (together with the Annex hereto) constitutes the
entire agreement of the parties with respect to its subject matter, and
supersedes all prior agreements and understandings of the parties, oral and
written, with respect thereto.

        8.5     This Agreement shall be governed by and construed in accordance
with the laws of the State of Delaware, without regard to the choice of law
provisions thereof.

        8.6     The headings contained in this Agreement are for
convenience of reference only and shall not in any way limit or affect the
meaning or interpretation of any of the terms or provisions of this Agreement.

        8.7     This Agreement may not be assigned by any party hereto without
the prior written consent of the other party.

        8.8     This Agreement shall inure to the benefit of, and be binding
upon, the parties hereto and their respective successors, legal representatives
and permitted assigns. Nothing contained in this Agreement is intended to confer
upon any person other than the parties hereto and their respective successors,
legal representatives and permitted assigns, any rights or remedies under or by
reason of this Agreement.

        8.9     In the event that any one or more of the provisions of this
Agreement or any application thereof shall be held to be invalid, illegal or
unenforceable in any respect, the validity, legality and enforceability of the
remaining provisions contained herein shall not in any way be affected or
impaired thereby, unless a manifest injustice or inequity would result from the
applicability or enforceability of such remaining provisions.

        8.10    The parties agree that irreparable harm will result in a breach
of Section 2.3 or 5.1 and that such a breach could not be adequately compensated
by monetary damages. Therefore, the parties agree that the Advisory Board shall
be entitled, in addition to any other right or remedy available to it, to
injunctive relief restraining such breach or threatened breach and to specific
performance, and in either case, no bond or other security shall be required in
connection therewith. Such remedies and all other remedies provided for in this
Agreement or available under law shall be cumulative and not exclusive.

        8.11    The parties shall endeavor to settle all disputes by amicable
negotiations. Any claim, dispute, disagreement or controversy that arises among
the parties relating to this Agreement ("Disputed Matter") that is not amicably
settled shall be referred to and settled by

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arbitration administered by the American Arbitration Association in accordance
with the Expedited Procedures of the Commercial Arbitration Rules of the
American Arbitration Association (the "AAA Rules") by a single arbitrator who is
mutually agreeable to the parties. If the parties are unable to agree upon an
arbitrator, one arbitrator shall be selected in accordance with the AAA Rules.
All proceedings in any such arbitration shall be conducted in Washington, D.C.
Each party to such arbitration proceeding shall bear its respective costs, fees
and expenses in connection with such arbitration. Upon a final determination by
the arbitrator with respect to the Disputed Matter, the arbitrator shall notify
the parties (such notice being the "Arbitration Order"). Any judgment on the
award rendered by the arbitrator may be entered in any court having jurisdiction
thereof. Jurisdiction of such arbitrator shall be exclusive as to disputes among
the parties relating to this Agreement and each of the parties agrees that this
agreement to arbitrate shall be specifically enforceable under the laws of the
respective domiciliary jurisdictions of the parties. None of the parties shall
have the right to appeal the Arbitration Order or otherwise to submit a Disputed
Matter to a court of law.

        8.12    This Agreement shall be executed in two or more counterparts,
each of which shall be deemed an original, but all of which together shall
constitute one and the same document.

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

THE ADVISORY BOARD COMPANY                THE CORPORATE EXECUTIVE BOARD COMPANY

By:     /s/ Jeffrey D. Zients             By:     /s/ Michael A. D'Amato
        -----------------------------             ----------------------

Name:   Jeffrey D. Zients                 Name:   Michael A. D'Amato

Title:  Chief Executive Officer           Title:  Executive Vice President

                                       7<PAGE>   1
                                                                   EXHIBIT 10.29

                                    GUARANTY

       THIS GUARANTY (the "Guaranty"), is made as of the ______ day of
_________________ by the undersigned party (the "Guarantor"), having a notice
address at The Watergate, 600 New Hampshire Avenue, N.W., Washington, D.C. 20037
Attention: Michael A. D'Amato to and for the benefit of The George Washington
University (the "Landlord"), having a notice address of c/o LaSalle Partners
Management Services, Inc., Suite 2400, 2000 Pennsylvania Avenue, N.W.,
Washington, D.C. 20006 and Office of Vice President & Treasurer, 2121 Eye
Street, N.W., Suite 701, Washington, D.C. 20052.

       WHEREAS, the Landlord has leased to THE CORPORATE ADVISORY BOARD COMPANY,
a Delaware corporation (the "Tenant"), under a lease dated June , 1998 (herein
called the "Lease"), certain space located in 2000 K Street, N.W. (the
"Property"); and

       WHEREAS, Guarantor and Tenant are both currently sharing space at The
Watergate, 600 New Hampshire Avenue, N.W. ("The Watergate") and are affiliated
corporations; and

       WHEREAS, Guarantor and Tenant have exceeded the capacity of the space at
The Watergate and therefore, Guarantor has asked Tenant to relocate; and

       WHEREAS, Tenant has agreed to relocate and has executed the Lease for
space in 2000 Pennsylvania Avenue, N.W. and the Landlord under such Lease is
willing to let space to Tenant only on the condition that Guarantor agree to
execute and deliver this guaranty.

       WHEREAS, Guarantor will receive a benefit from the ability of Tenant to
relocate to the premises demised by the Lease in the form of additional space at
the site where Guarantor presently leases space, and Guarantor is therefore
willing to execute and deliver this Guaranty.

       NOW THEREFORE, in consideration of the premises, and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Guarantor agrees with the Landlord as follows:

       1.     The Guarantor unconditionally and irrevocably guarantees that all
sums stated in the Lease to be payable by the Tenant or sums equal thereto will
be promptly paid in full when due in accordance with the Lease, and that the
Tenant will perform and observe each and every covenant, agreement, term and
condition in the Lease required to be performed or observed by the Tenant.
Guarantor further unconditionally and irrevocably guarantees payment to Landlord
on demand any amounts which are paid to Landlord by the Tenant pursuant to the
Lease and which are subsequently set aside as preferential transfers under
Section 547 of the Bankruptcy Code. This Guaranty is irrevocable, unconditional
and absolute, and if for any reason any such sums shall not be paid promptly
when due, the Guarantor will, promptly after notice thereof and prior to the
expiration of any period of grace provided for in said instruments for the
making of payment of any such sums, pay the same to the person entitled thereto
pursuant to the Lease regardless of (a) any defenses or rights of set-off or
counterclaims which the Tenant may have or assert against the Landlord;
provided, however, that any such payment by the Guarantor shall not constitute a
waiver of any defense or claim which the Tenant may have against the Landlord,
(b) whether the Landlord shall have taken any steps to enforce any rights
against the Tenant or any

<PAGE>   2

other person to collect such sum or any part thereof, (c) the termination of the
Lease or the enforcement of any other remedy thereunder as a result of the
default of the Tenant thereunder, or (d) any other condition or contingency. The
Guarantor also agrees to pay to such person such further amount as shall be
sufficient to cover the cost and expense of collecting such sums or any part
thereof or of otherwise enforcing this Guaranty, including, in any case,
reasonable compensation to its attorneys for all services rendered in connection
therewith. Upon the Tenant's failure to perform or observe any covenant,
agreement, term or condition in the Lease to be performed or observed by the
Tenant, the Guarantor will, promptly after notice thereof and prior to the
expiration of any period of grace provided for in any said instrument for the
performance or observance of the same, perform and observe the same or cause the
same promptly to be performed and observed.

       2.     (a)    The obligations, covenants, agreements and duties of the
Guarantor under this Guaranty shall in no way be affected or impaired by reason
of the happening from time to time of any of the following, although without
notice to or the further consent of the Guarantor:

              (i)    the waiver by the Landlord of the performance or observance
       by the Tenant, the Guarantor or any other party or parties of any of the
       agreements, covenants, terms or conditions contained in the Lease or this
       Guaranty; or

              (ii)   the extension, in whole or in part, of the time for payment
       by the Tenant or the Guarantor of any sums owing or payable under the
       Lease or this Guaranty, or of any other sums or obligations under or
       arising out of or on account of the Lease or this Guaranty, or the
       renewal of the Lease or this Guaranty; or

              (iii)  any assignment of the Lease or subletting of the Property
       or any part thereof; or

              (iv)   the modification or amendment (whether material or
       otherwise) of any of the obligations of the Tenant or the Guarantor under
       the Lease or this Guaranty; or

              (v)    the doing or the omission of any of the acts referred to in
       the Lease or this Guaranty (including, without limitation, the giving of
       any consent referred to therein); or

              (vi)   any failure, omission or delay on the part of the Landlord
       to enforce, assert or exercise any right, power or remedy conferred on or
       available to the Landlord in or by the Lease or the Guaranty, or any
       action on the part of the Landlord granting indulgence or extension in
       any form whatsoever; or

              (vii)  the voluntary or involuntary liquidation, dissolution, sale
       of all or substantially all of the assets, marshaling of assets and
       liabilities, receivership, conservatorship, insolvency, bankruptcy,
       assignment for the benefit of creditors, reorganization, arrangement,
       composition or readjustment of, or other similar proceeding affecting the
       Tenant or the Guarantor or any of their assets; or

              (viii) the release of the Tenant or the Guarantor from the
       performance or observance of any of the agreements, covenants, terms or
       conditions contained in the Lease or this Guaranty by operation of law.

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              (b)    Guarantor further covenants and agrees that neither its
obligation to make payment in accordance with the terms of this Guaranty nor any
remedy for the enforcement thereof shall be impaired, modified, changed,
released or limited in any manner whatsoever by any impairment, modification,
change, release or limitation of the liability of Tenant or its estate in
bankruptcy or any remedy for the enforcement thereof resulting from the
operation of any present or future provision of the Bankruptcy Reform Act of
1978 or other statute, or from the decision of any court, nor shall such
obligation or remedy for enforcement be impaired, modified, changed, released or
limited in any manner by such event of bankruptcy.

              (c)    The Guarantor hereby expressly waives, to the extent not
prohibited by law, for itself and all those claiming under the Guarantor (i) any
right the Guarantor may now or hereafter have to require the Landlord to proceed
first against the Tenant upon any obligation or liability of the Tenant that is
guaranteed by the Guarantor hereunder, (ii) any right the Guarantor may now or
hereafter have to any hearing prior to the attachment of any real or personal
property of the Guarantor to satisfy the obligations of the Guarantor hereunder,
and (iii) the benefits of any present or future constitution, statute or rule of
law which exempts property from liability for debt.

       3.     In the event of the rejection or disaffirmance of the Lease by the
Tenant or the Tenant's trustee in bankruptcy pursuant to bankruptcy law or any
other law affecting creditors' rights, the Guarantor will, and does hereby
(without the necessity of any further agreement or act), assume all obligations
and liabilities of the Tenant under the Lease to the same extent as if (a)
Guarantor were originally named the Tenant under the Lease, and (b) there had
been no such rejection or disaffirmance, and the Guarantor will confirm such
assumption in writing at the request of the Landlord upon or after such
rejection or disaffirmance; the Guarantor shall, upon such assumption (to the
extent permitted by law), have all rights of the Tenant under the Lease.

       4.     Notice of acceptance of this Guaranty and notice of any
obligations or liabilities contracted or incurred by the Tenant are hereby
waived by the Guarantor.

       5.     This Guaranty may not be modified or amended except by a written
agreement duly executed by the Guarantor with the consent in writing of the
Landlord.

       6.     The Guarantor hereby covenants and represents that (a) neither the
execution, delivery or performance of this Guaranty or the Lease, nor the
consummation of the transactions herein or therein contemplated, nor compliance
with the terms and provisions hereof or thereof conflicts or will conflict with
or result or will result in a breach of or constitutes or will constitute a
default under (i) the organizational documents or other charter documents or
by-laws, if any, of the Tenant, (ii) any law or any order, writ, injunction or
decree of any court or governmental authority or (iii) any agreement or
instrument to which the Guarantor or the Tenant is a party or by which Guarantor
or the Tenant is bound; (b) the Guarantor is not engaged in any litigation which
will or may adversely affect its ability to carry out any of the terms and
provisions of this Guaranty.

       7.     This is an unconditional guaranty of payment, not merely of
collection. The Guarantor's liability hereunder shall be primary and not
secondary, and shall be joint and several with that of the Tenant. The Landlord
may proceed against the Guarantor under this Guaranty

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<PAGE>   4

without initiating or exhausting its remedy or remedies against the Tenant, and
may proceed against the Tenant and/or the Guarantor separately or concurrently.
If more than one party constitutes Guarantor, then all obligations and covenants
set forth herein shall be the joint and several obligations and covenants of the
undersigned parties collectively constituting Guarantor.

       8.     The Guarantor hereby warrants and represents that as of the date
hereof, there has been no material change in its financial condition from that
reflected in any financial statements previously submitted to Landlord, and
since the date of such statement, if any, the business, property and assets of
the Guarantor have not been adversely affected in any way.

       9.     If any term or provision of this Guaranty shall be determined to
be illegal or unforceable, all other terms and provisions hereof shall
nevertheless remain effective and shall be enforced to the fullest extent
permitted by law.

       10.    Any notice which the Landlord may elect to send to the Guarantor
shall be binding upon the Guarantor if mailed to it at the address set forth
above or its last address known to the Landlord, by United States Certified or
Registered Mail, Return Receipt Requested.

       11.    This Guaranty shall be construed in accordance with the laws of
the District of Columbia. Guarantor agrees that any litigation arising out of,
or related to, this Guaranty or the Lease shall be brought in the courts of the
District of Columbia or in the United States District Court for the District of
Columbia, and the Guarantor hereby consents to the venue of such courts.
Guarantor consents to service of process and any pleading relating to any action
between Landlord and Guarantor at the Demised Premises, as defined in the Lease,
provided however, that nothing herein shall be construed as requiring such
service at the Demised Premises.

       12.    This Guaranty shall be binding upon, Guarantor, its heirs,
personal representatives, successors and assigns and shall inure to the benefit
of, Landlord, its successors and assigns.

       13.    This Guaranty shall expire on March 31, 2002 provided the
following conditions have been met:

              (a)    The Tenant is not then in default under the Lease.

              (b)    Guarantor has provided to Landlord audited financial
statements for The Corporate Advisory Board Company prepared by Arthur Anderson
or other national accounting firm acceptable to Landlord in its reasonable
discretion for two (2) consecutive Fiscal Years ending December 31 which show
for each such Fiscal Year that the lesser of operating income or income before
provision of income taxes (after option repurchase and non-recurring
compensation and interest income as shown on such financial statements) exceeds
ten million dollars ($10,000,000).

              (c)    The second of the two (2) consecutive Fiscal Years referred
to above ends on December 31, 2001.

              (d)    Landlord has confirmed, within ten (10) business days of
the submission of the financial statements referenced in (b). above that for
each Fiscal Year shown on such

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financial statements that the lesser of operating income or income before
provision of income taxes (after option repurchase and non-recurring
compensation and interest income as shown on such financial statements) exceeds
ten million dollars ($10,000,000) and that the Tenant is not in default under
the Lease.

              (e)    The financial statements are delivered to Landlord no later
than March 15, 2002.

In the event that the financial statements required under subparagraph (b) are
submitted for years subsequent to Fiscal Year 2001, then the Guaranty will
expire on the first day of the month following the month in which Landlord
confirms the information in such financial statements as required in
subparagraph (d) above. In the event that the financial statements for Fiscal
Years 2000 and 2001 are submitted to Landlord later than March 15, 2002, then
the Guaranty will not expire until the first day of the month following the
month in which Landlord confirms the information in the financial statements
required by subparagraph (d) above.

       The date of the expiration of this Guaranty is referred to herein and in
the Lease as the "Burnoff Date".

       IN WITNESS WHEREOF, the Guarantor has caused this Guaranty to be executed
as of the date first above written.

<TABLE>
<CAPTION>
                                       GUARANTOR:

Attest/Witness:                        THE ADVISORY BOARD COMPANY

<S>                                    <C>
                                       By:                               (SEAL)
--------------------------------           ------------------------------
Assistant Secretary                         President
</TABLE>

                                       5

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