Document:

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                                                                    Exhibit 10.1

                           MICROSTRATEGY INCORPORATED
                           --------------------------

                          REGISTRATION RIGHTS AGREEMENT
                          -----------------------------

         THIS REGISTRATION RIGHTS AGREEMENT (the "Agreement") dated as of August
28, 2001 is entered into by and among MicroStrategy Incorporated, a Delaware
corporation (the "Company"), and the individuals and entities listed on Exhibit
                                                                        -------
A attached hereto (the "Purchasers").
-

                                    Recitals
                                    --------

         WHEREAS, the Company and the Purchasers, among others, have entered
into an Exchange Agreement dated as of August 28, 2001, pursuant to which the
Company has issued and delivered to the Purchasers certain shares of capital
stock of the Company; and

         WHEREAS, the Company and the Purchasers desire to provide for certain
arrangements with respect to the registration of such shares under the
Securities Act of 1933, as amended.

         NOW, THEREFORE, in consideration of the mutual promises and covenants
contained in this Agreement, the parties hereto agree as follows:

      1. Certain Definitions.
         -------------------

         As used in this Agreement, the following terms shall have the following
respective meanings:

                  "Commission" means the Securities and Exchange Commission, or
                   ----------
any other federal agency at the time administering the Securities Act.

                  "Common Stock" means the Class A Common Stock, $0.001 par
                   ------------
value per share, of the Company.

                  "Company" means MicroStrategy Incorporated, a Delaware
                   -------
corporation.

                  "Exchange Act" means the Securities Exchange Act of 1934, as
                   ------------
amended, or any successor federal statute, and the rules and regulations of the
Commission issued under such Act, as they each may, from time to time, be in
effect.

                  "Prospectus" means the prospectus included in any Registration
                   ----------
Statement, as amended or supplemented by an amendment or prospectus supplement,
including post-effective amendments, and all material incorporated by reference
or deemed to be incorporated by reference in such Prospectus.

                  "Exchange Agreement" means the Exchange Agreement by and
                   ------------------
among, inter alia, the Company and the Purchasers, dated as of August 28, 2001.

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                  "Purchaser Registrable Shares" means the Registrable Shares
                   ----------------------------
held by Stockholders.

                  "Purchasers" means the individuals and entities listed on
                   ----------
Exhibit A attached hereto.
---------

                  "Registration Statement" means a registration statement filed
                   ----------------------
on Form S-3 (or such other form as the Company is then eligible to use) by the
Company with the Commission in accordance with Section 2.1.

                  "Registration Expenses" means the expenses described in
                   ---------------------
Section 2.4.

                  "Registrable Shares" means (i) the shares of Common Stock
                   ------------------
issued to the Purchasers pursuant to the Exchange Agreement and (ii) any shares
of Common Stock issued in respect of such shares of Common Stock (because of
stock splits, stock dividends, reclassifications, recapitalizations, or similar
events); provided, however, that shares of Common Stock which are Registrable
         -----------------
Shares shall cease to be Registrable Shares (x) upon any sale pursuant to a
Registration Statement or Rule 144 under the Securities Act, (y) upon any sale
in any manner to a person or entity which is not entitled to the rights provided
by this Agreement or (z) at such time such shares become and remain eligible for
resale without limitation pursuant to Rule 144 under the Securities Act.

                  "Securities Act" means the Securities Act of 1933, as amended,
                   --------------
or any successor federal statute, and the rules and regulations of the
Commission issued under such Act, as they each may, from time to time, be in
effect.

                  "Selling Stockholder" means any Stockholder owning Registrable
                   -------------------
Shares included in a Registration Statement.

                  "Stockholders" means the Purchasers, their successors or
                   ------------
assigns.

      2. Registration Rights
         -------------------

         2.1    Required Registration. The Company shall file a Registration
                ---------------------
Statement, registering the Registrable Shares owned by the Stockholders within
fifteen (15) business days after the consummation of the transactions
contemplated by the Exchange Agreement.

         2.2    Registration Procedures.
                -----------------------

                (a) If and whenever the Company is required by the provisions of
this Agreement to effect the registration of any Registrable Shares under the
Securities Act, the Company shall:

                        (i) file with the Commission a Registration Statement
with respect to such Registrable Shares and use commercially reasonable efforts
to cause that Registration Statement to become effective as soon as practicable;

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                        (ii) promptly prepare and file with the Commission any
amendments and supplements to the Registration Statement and the prospectus
included in the Registration Statement as may be necessary to comply with the
provisions of the Securities Act (including the anti-fraud provisions thereof)
and to keep the Registration Statement effective until the first anniversary of
the closing of the Exchange Agreement or such lesser period until all such
Registrable Shares are sold;

                        (iii) promptly furnish to each Selling Stockholder such
reasonable number of copies of the Prospectus, including any preliminary
Prospectus, in conformity with the requirements of the Securities Act, and such
other documents as such Selling Stockholder may reasonably request in order to
facilitate the public sale or other disposition of the Registrable Shares owned
by such Selling Stockholder;

                        (iv) promptly use its best efforts to register or
qualify the Registrable Shares covered by the Registration Statement under the
securities or Blue Sky laws of such states as the Selling Stockholders shall
reasonably request, and do any and all other acts and things that may be
necessary or desirable to enable the Selling Stockholders to consummate the
public sale or other disposition in such states of the Registrable Shares owned
by the Selling Stockholder; provided, however, that the Company shall not be
                            -----------------
required in connection with this paragraph (iv) to qualify as a foreign
corporation or execute a general consent to service of process in any
jurisdiction;

                        (v) promptly cause all such Registrable Shares to be
listed on each securities exchange or automated quotation system on which
similar securities issued by the Company are then listed;

                        (vi) promptly make available for inspection by the
Selling Stockholders, any managing underwriter participating in any disposition
pursuant to such Registration Statement, and any attorney or accountant or other
agent retained by any such underwriter or selected by the Selling Stockholders
(collectively, the "Selling Stockholder Parties"), all financial and other
records, pertinent corporate documents and properties of the Company and cause
the Company's officers, directors, employees and independent accountants to
supply all information reasonably requested by any such seller, underwriter,
attorney, accountant or agent in connection with such Registration Statement;
provided, however, that each Selling Stockholder agrees that he, she or it will,
-----------------
and will cause the Selling Stockholder Parties to, keep such information
confidential and will not, and will cause the Selling Stockholder Parties not
to, disclose, divulge or use such information for any purpose other than the
purposes contemplated by this Agreement, except as may otherwise be required by
law after taking reasonable steps to minimize such disclosure;

                        (vii) promptly notify each Selling Stockholder, after
it shall receive notice thereof, of the time when such Registration Statement
has become effective or a supplement to any Prospectus forming a part of such
Registration Statement has been filed; and

                        (viii) following the effectiveness of such Registration
Statement, promptly notify each seller of such Registrable Shares of any request
by the Commission for the amending or supplementing of such Registration
Statement or Prospectus.

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                (b) If the Company has delivered a Prospectus to the Selling
Stockholders and after having done so the Prospectus is amended to comply with
the requirements of the Securities Act, the Company shall promptly notify the
Selling Stockholders and, if requested, the Selling Stockholders shall
immediately cease making offers of Registrable Shares and return all
Prospectuses to the Company. The Company shall promptly provide the Selling
Stockholders with revised Prospectuses and, following receipt of the revised
Prospectuses, the Selling Stockholders shall be free to resume making offers of
the Registrable Shares.

                (c) In the event that, in the good faith judgment of the
Company's Board of Directors, there is a valid business purpose or reason to
suspend use of a Prospectus included in a Registration Statement, or if such
suspension is required by applicable law, the Company shall notify all Selling
Stockholders to such effect, and, upon receipt of such notice, each such Selling
Stockholder shall immediately discontinue any sales of Registrable Shares
pursuant to such Registration Statement until such Selling Stockholder has
received copies of a supplemented or amended Prospectus or until such Selling
Stockholder is advised in writing by the Company that the then current
Prospectus may be used and has received copies of any additional or supplemental
filings that are incorporated or deemed incorporated by reference in such
Prospectus. Notwithstanding anything to the contrary herein, the Company shall
not exercise its rights under this Section 2.2(c) to suspend sales of
Registrable Shares for a period in excess of 90 trading days out of any 365
calendar day period.

         2.3    Allocation of Expenses. The Company will pay all Registration
                ----------------------
Expenses for all registrations under this Agreement. For purposes of this
Section, the term "Registration Expenses" shall mean all expenses incurred by
the Company in complying with this Agreement, including, without limitation, all
registration and filing fees, exchange listing fees, printing expenses, fees and
expenses of counsel for the Company and the reasonable fees and expenses of one
counsel selected by the Selling Stockholders to represent the Selling
Stockholders, state Blue Sky fees and expenses, and the expense of any special
audits incident to or required by any such registration, but excluding
underwriting discounts, selling commissions and the fees and expenses of Selling
Stockholders' own counsel (other than the counsel selected to represent all
Selling Stockholders).

         2.4    Indemnification and Contribution.
                --------------------------------

                (a) In the event of any registration of any of the Registrable
Shares under the Securities Act pursuant to this Agreement, the Company will
indemnify and hold harmless each Selling Stockholder, each underwriter of such
Registrable Shares, and each other person, if any, who controls such Selling
Stockholder, its directors and officers, and any underwriter within the meaning
of the Securities Act or the Exchange Act against any losses, claims, damages or
liabilities, joint or several, to which such Selling Stockholder, its directors
and officers, or any underwriter or controlling person may become subject under
the Securities Act, the Exchange Act, state securities or Blue Sky laws or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of any material fact contained in any Registration Statement
under which such Registrable Shares were registered under the Securities Act,
any preliminary prospectus or final prospectus contained in the Registration
Statement, or any

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amendment or supplement to such Registration Statement, or arise out of or
are based upon the omission or alleged omission to state a material fact
required to be stated therein or necessary to make the statements therein not
misleading; and the Company will reimburse such Selling Stockholder, its
directors and officers, any underwriter and each such controlling person for any
legal or any other expenses reasonably incurred by such Selling Stockholder, its
directors and officers, or any underwriter or controlling person in connection
with investigating or defending any such loss, claim, damage, liability or
action; provided, however, that the Company will not be liable in any such case
        -----------------
to the extent that any such loss, claim, damage or liability arises out of or is
based upon any untrue statement or omission made in such Registration Statement,
preliminary prospectus or prospectus, or any such amendment or supplement, in
reliance upon and in conformity with information furnished to the Company, in
writing, by or on behalf of such Selling Stockholder, underwriter or controlling
person specifically for use in the preparation thereof.

                (b) In the event of any registration of any of the Registrable
Shares under the Securities Act pursuant to this Agreement, each Selling
Stockholder, severally and not jointly, will indemnify and hold harmless the
Company, each of its directors and officers and each underwriter (if any) and
each person, if any, who controls the Company or any such underwriter within the
meaning of the Securities Act or the Exchange Act, against any losses, claims,
damages or liabilities, joint or several, to which the Company, such directors
and officers, underwriter or controlling person may become subject under the
Securities Act, Exchange Act, state securities or Blue Sky laws or otherwise,
insofar as such losses, claims, damages or liabilities (or actions in respect
thereof) arise out of or are based upon any untrue statement or alleged untrue
statement of a material fact contained in any Registration Statement under which
such Registrable Shares were registered under the Securities Act, any
preliminary prospectus or final prospectus contained in the Registration
Statement, or any amendment or supplement to the Registration Statement, or
arise out of or are based upon any omission or alleged omission to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading, if the statement or omission was made in reliance upon
and in conformity with information relating to such Selling Stockholder
furnished in writing to the Company by or on behalf of such Selling Stockholder
specifically for use in connection with the preparation of such Registration
Statement, prospectus, amendment or supplement.

                (c) Each party entitled to indemnification under this Section
(the "Indemnified Party") shall give notice to the party required to provide
indemnification (the "Indemnifying Party") promptly after such Indemnified Party
has actual knowledge of any claim as to which indemnity may be sought, and shall
permit the Indemnifying Party to assume the defense of any such claim or any
litigation resulting therefrom; provided, that counsel for the Indemnifying
                                --------
Party, who shall conduct the defense of such claim or litigation, shall be
approved by the Indemnified Party (whose approval shall not be unreasonably
withheld); and, provided, further, that the failure of any Indemnified Party to
                -----------------
give notice as provided herein shall not relieve the Indemnifying Party of its
obligations under this Section except to the extent that the Indemnifying Party
is adversely affected by such failure. The Indemnified Party may participate in
such defense at such party's expense; provided, however, that the Indemnifying
                                      -----------------
Party shall pay such expense if representation of such Indemnified Party by the
counsel retained by the Indemnifying Party would be inappropriate due to actual
or potential differing interests between the Indemnified Party and any other
party represented by such counsel in such proceeding;

                                       5

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provided further that in no event shall the Indemnifying Party be required
-------- -------
to pay the expenses of more than one law firm per jurisdiction as counsel for
the Indemnified Party. The Indemnifying Party also shall be responsible for the
expenses of such defense if the Indemnifying Party does not elect to assume such
defense. No Indemnifying Party, in the defense of any such claim or litigation
shall, except with the consent of each Indemnified Party, consent to entry of
any judgment or enter into any settlement which does not include as an
unconditional term thereof the giving by the claimant or plaintiff to such
Indemnified Party of a release from all liability in respect of such claim or
litigation, and no Indemnified Party shall consent to entry of any judgment or
settle such claim or litigation without the prior written consent of the
Indemnifying Party, which consent shall not be unreasonably withheld.

                (d) In order to provide for just and equitable contribution in
circumstances in which the indemnification provided for in this Section 2.4 is
due in accordance with its terms but for any reason is held to be unavailable to
an Indemnified Party in respect to any losses, claims, damages and liabilities
referred to herein, then the Indemnifying Party shall, in lieu of indemnifying
such Indemnified Party, contribute to the amount paid or payable by such
Indemnified Party as a result of such losses, claims, damages or liabilities to
which such party may be subject in such proportion as is appropriate to reflect
the relative fault of the Company on the one hand and the Selling Stockholders
on the other in connection with the statements or omissions which resulted in
such losses, claims, damages or liabilities, as well as any other relevant
equitable considerations. The relative fault of the Company and the Selling
Stockholders shall be determined by reference to, among other things, whether
the untrue or alleged untrue statement of material fact related to information
supplied by the Company or the Selling Stockholders and the parties' relative
intent, knowledge, access to information and opportunity to correct or prevent
such statement or omission. The Company and the Selling Stockholders agree that
it would not be just and equitable if contribution pursuant to this Section 2.4
were determined by pro rata allocation or by any other method of allocation
which does not take account of the equitable considerations referred to above.
Notwithstanding the provisions of this paragraph of Section 2.4, in no case
shall any one Selling Stockholder be liable or responsible for any amount in
excess of the net proceeds received by such Selling Stockholder from the
offering of Registrable Shares; provided, however, that no person guilty of
                                --------  -------
fraudulent misrepresentation (within the meaning of Section 11(f) of the
Securities Act) shall be entitled to contribution from any person who was not
guilty of such fraudulent misrepresentation. Any party entitled to contribution
will, promptly after receipt of notice of commencement of any action, suit or
proceeding against such party in respect of which a claim for contribution may
be made against another party or parties under this Section, notify such party
or parties from whom contribution may be sought, but the omission so to notify
such party or parties from whom contribution may be sought shall not relieve
such party from any other obligation it or they may have thereunder or otherwise
under this Section.

                (e) No party shall be liable for indemnification or contribution
with respect to any action, suit, proceeding or claim settled without its prior
written consent, which consent shall not be unreasonably withheld.

         2.5    Information by Holder. Each holder of Registrable Shares
                ---------------------
included in any registration shall furnish to the Company such information
regarding such holder and the distribution proposed by such holder as the
Company may reasonably request in writing and as

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shall be required in connection with any registration, qualification or
compliance referred to in this Agreement.

         2.6 "Stand-Off" Agreement; Confidentiality of Notices. Each
              ------------------------------------------------
Stockholder, if requested by the Company and the managing underwriter of an
underwritten public offering by the Company of Common Stock, shall not sell or
otherwise transfer or dispose of any Registrable Shares or other securities of
the Company held by such Stockholder for a period of 90 days following the
effective date of a registration statement covering securities of the Company to
be sold on its behalf to the public in an underwritten offering.

         The Company may impose stop-transfer instructions with respect to the
Registrable Shares or other securities subject to the foregoing restriction
until the end of such 90-day period.

         Any Stockholder receiving any written notice from the Company regarding
the Company's plans to file a registration statement shall treat such notice
confidentially and shall not disclose such information to any person other than
as necessary to exercise its rights under this Agreement.

         2.7    Rule 144 Requirements.  The Company agrees to:
                ---------------------

                (a) make and keep current public information about the
Company available, as those terms are understood and defined in Rule 144;

                (b) use its best efforts to file with the Commission in a timely
manner all reports and other documents required of the Company under the
Securities Act and the Exchange Act (at any time is subject to such reporting
requirements); and

                (c) furnish to any holder of Registrable Shares upon request (i)
a written statement by the Company as to its compliance with the reporting
requirements of Rule 144 and of the Securities Act and the Exchange Act (at any
time it is subject to such reporting requirements), (ii) a copy of the most
recent annual or quarterly report of the Company, and (iii) such other reports
and documents of the Company as such holder may reasonably request to avail
itself of any similar rule or regulation of the Commission allowing it to sell
any such securities without registration.

         2.8 Termination. All of the Company's obligations to keep the
             -----------
Registration Statement referenced in Sections 2.1 of this Agreement effective
shall terminate one (1) year after the closing of the transactions contemplated
by the Exchange Agreement.

      3. General.
         -------

                (a)  Severability.  The invalidity or unenforceability of any
provision of this Agreement shall not affect the validity or enforceability of
any other provision of this Agreement.

                (b)  Specific Performance.  In addition to any and all other
                     --------------------
remedies that may be available at law in the event of any breach of this
Agreement, each Purchaser shall be entitled to specific performance of the
agreements and obligations of the Company hereunder

                                       7

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and to such other injunctive or other equitable relief as may be granted by a
court of competent jurisdiction.

                (c)  Governing Law.  This Agreement shall be governed by and
                     -------------
construed in accordance with the internal laws of the State of Delaware (without
reference to the conflicts of law provisions thereof).

                (d)  Notices. All notices, requests, consents, and other
                     -------
communications under this Agreement shall be in writing and shall be deemed
delivered (i) two business days after being sent by registered or certified
mail, return receipt requested, postage prepaid or (ii) one business day after
being sent via a reputable nationwide overnight courier service guaranteeing
next business day delivery, in each case to the intended recipient as set forth
below:

         If to the Company, at 1861 International Drive, McLean, Virginia 22102,
Attention: President and General Counsel, or at such other address or addresses
as may have been furnished in writing by the Company to the Purchasers, with a
copy to Thomas S. Ward, Esq., Hale and Dorr LLP, 60 State Street, Boston,
Massachusetts 02109; or

         If to a Purchaser, at his or its address set forth on Exhibit A, or at
                                                               ---------
such other address or addresses as may have been furnished to the Company in
writing by such Purchaser.

         Any party may give any notice, request, consent or other communication
under this Agreement using any other means (including, without limitation,
personal delivery, messenger service, telecopy, first class mail or electronic
mail), but no such notice, request, consent or other communication shall be
deemed to have been duly given unless and until it is actually received by the
party for whom it is intended. Any party may change the address to which
notices, requests, consents or other communications hereunder are to be
delivered by giving the other parties notice in the manner set forth in this
Section.

                (e) Complete Agreement; Assignment. This Agreement, the
                    ------------------------------
Exchange Agreement and the Release constitute the entire agreement and
understanding of the parties hereto with respect to the subject matter hereof
and supersedes all prior agreements and understandings relating to such subject
matter. No party may assign either this Agreement or any of its rights,
interests or obligations hereunder without the prior written approval of the
other parties hereof.

                (f) Amendments and Waivers. Any term of this Agreement may be
                    ----------------------
amended or terminated and the observance of any term of this Agreement may be
waived with respect to all parties to this Agreement (either generally or in a
particular instance and either retroactively or prospectively), with the written
consent of the Company and the holders of at least 66 2/3% of the Registrable
Shares, including Aether Capital LLC (so long as it holds any Registrable
Shares). Any such amendment, termination or waiver effected in accordance with
this Section 3.1(f) shall be binding on all parties hereto, even if they do not
execute such consent and the Company. No waivers of or exceptions to any term,
condition or provision of this Agreement, in any one or more instances, shall be
deemed to be, or construed as, a further or continuing waiver of any such term,
condition or provision.

                                       8

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                (g) Pronouns. Whenever the context may require, any pronouns
                    --------
used in this Agreement shall include the corresponding masculine, feminine or
neuter forms, and the singular form of nouns and pronouns shall include the
plural, and vice versa.

                (h) Counterparts; Facsimile Signatures.  This Agreement may be
                    ----------------------------------
executed in any number of counterparts, each of which shall be deemed to be an
original, and all of which together shall constitute one and the same document.
This Agreement may be executed by facsimile signatures.

                (i) Section Headings.  The section headings are for the
                    ----------------
convenience of the parties and in no way alter, modify, amend, limit or restrict
the contractual obligations of the parties.

              [Remainder of this page is intentionally left blank]
              ----------------------------------------------------

                                       9

<PAGE>

          [Counterpart signature page to Registration Rights Agreement]

         Executed as of the date first written above.

                                    MICROSTRATEGY INCORPORATED

                                        /s/ Eric F. Brown
                                    By:________________________

                                    Name:  Eric F. Brown

                                    Title: President and Chief Financial Officer

                                       10

<PAGE>

          [Counterpart signature page to Registration Rights Agreement]

         Executed as of the date first written above.

                                        AETHER CAPITAL LLC

                                        By: Aether Systems, Inc.,
                                            its Sole Member

                                            /s/ David C. Reymann
                                        By:________________________________

                                        Name:  David C. Reymann

                                        Title: Chief Financial Officer

                                       11

<PAGE>

          [Counterpart signature page to Registration Rights Agreement]

         Executed as of the date first written above.

                                        SNOWDON LTD. PARTNERSHIP

                                            /s/ Jon C. Baker
                                        By:________________________________

                                        Name:  Jon C. Baker

                                        Title: Managing Member

                                       12

<PAGE>

          [Counterpart signature page to Registration Rights Agreement]

         Executed as of the date first written above.

                                        VALHALLA CAPITAL L.P.

                                        By:  Valhalla Capital Management LLC

                                            /s/ Nancy Casey
                                        By:________________________________

                                        Name:  Nancy Casey

                                        Title: Managing Member

                                       13

<PAGE>

          [Counterpart signature page to Registration Rights Agreement]

         Executed as of the date first written above.

                                         NEW VENTURE PARTNERS IV, L.P.

                                             /s/ Howard D. Wolfe, Sr.
                                         By:____________________________

                                         Name:  Howard D. Wolfe, Sr.

                                         Title: General Partner

                                       14

<PAGE>

          [Counterpart signature page to Registration Rights Agreement]

         Executed as of the date first written above.

                                     By: /s/ David R. Wilmerding, III
                                         ------------------------------------

                                        Name: David R. Wilmerding, III

                                       15

<PAGE>

          [Counterpart signature page to Registration Rights Agreement]

         Executed as of the date first written above.

                                          By: /s/ Nancy Casey
                                             -------------------------------

                                          Name: Nancy Casey

                                          By: /s/ Art Marks
                                              ------------------------------

                                          Name: Art Marks

                                       16

<PAGE>

          [Counterpart signature page to Registration Rights Agreement]

         Executed as of the date first written above.

                                         By: /s/ Jon C. Baker
                                             ------------------------------

                                         Name: Jon C. Baker

                                       17

<PAGE>

                                                                       Exhibit A
                                                                       ---------

                                   Purchasers
                                   ----------

Name and Address
----------------
Aether Capital LLC
c/o Aether Systems, Inc.
11460 Cronridge Drive
Owings Mills, Maryland 21117

Snowdon Ltd. Partnership
c/o Nevis Capital Management
1119 St. Paul Street
Baltimore, MD 21202

Jon C. Baker
c/o Nevis Capital Management
1119 St. Paul Street
Baltimore, MD 21202

David R. Wilmerding, III
c/o Nevis Capital Management
1119 St. Paul Street
Baltimore, MD 21202

New Venture Partners IV, L.P.
Attn: Howard Wolfe
1119 St. Paul Street
Baltimore, MD 21202

Nancy Casey & Art Marks
10836 Pleasant Hill Drive
Potomac, MD 20854

Valhalla Capital L.P.
10836 Pleasant Hill Drive
Potomac, MD 20854

                                       A-1EXHIBIT 10.1

                                                                  Execution Copy

================================================================================

                               FIFTH AMENDMENT TO

                     AMENDED AND RESTATED CREDIT AGREEMENT

                           Dated as of March 14, 2001

                                     Among

                  LABORATORY CORPORATION OF AMERICA HOLDINGS,
                                  as Borrower,

                            THE BANKS NAMED HEREIN,
                                 as Banks, and

                          CREDIT SUISSE FIRST BOSTON,
                            as Administrative Agent

================================================================================

<PAGE>

                               TABLE OF CONTENTS

                             ----------------------

                                                                            Page
                                                                            ----

                                   ARTICLE I
                                   AMENDMENTS

SECTION 1.01  Amendment to Mandatory Prepayment Provision......................1
SECTION 1.02  Amendment to Acquisition Covenant................................2
SECTION 1.03  Amendment to Debt Covenant.......................................2

                                   ARTICLE II
                         REPRESENTATIONS AND WARRANTIES

SECTION 2.01  Representations and Warranties of the Borrower...................2

                                  ARTICLE III
                                 MISCELLANEOUS

SECTION 3.01  Governing Law....................................................3
SECTION 3.02  Execution in Counterparts........................................3
SECTION 3.03  Effect on the Credit Agreement...................................3

<PAGE>

                         FIFTH AMENDMENT TO AMENDED AND
                           RESTATED CREDIT AGREEMENT

     FIFTH AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT, dated as of
March 14, 2001 (this "Amendment") among LABORATORY CORPORATION OF AMERICA
HOLDINGS, a Delaware corporation (the "Borrower"), the banks, financial
institutions and other institutional lenders (the "Banks") listed on the
signature pages hereof, and CREDIT SUISSE FIRST BOSTON, as administrative agent
(the "Administrative Agent") for the Lenders hereunder.

                             PRELIMINARY STATEMENTS

     The parties hereto (i) have entered into an Amended and Restated Credit
Agreement dated as of March 31, 1997, as amended as of September 30, 1997,
February 25, 1998, May 7, 1999 and June 7, 2000 (the "Credit Agreement")
providing for, among other things, the Lenders to lend to the Borrower up to
$1,143,750,000 on the terms and subject to the conditions set forth therein and
(ii) desire to amend the Credit Agreement in the manner set forth herein. Each
capitalized term used but not defined herein shall have the meaning ascribed
thereto in the Credit Agreement.

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
and agreements contained herein, the parties hereto hereby agree as follows:

                                   ARTICLE I

                                   AMENDMENTS

     SECTION 1.01 Amendment to Mandatory Prepayment Provision. Section
2.05(b)(ii) of the Credit Agreement is hereby amended by renumbering such
subsection as Section 2.05(b)(ii)(A) and inserting the following immediately
thereafter:

          "(B) Zero Coupon Bond Issuance. The Borrower shall, on the date of
     receipt of the Net Cash Proceeds from the sale and issuance by the
     Borrower or any of its Subsidiaries of any Debt permitted pursuant to
     Section 5.02(j)(xiv), apply such Net Cash Proceeds to the Term Advances,
     in prepayment of the installments thereof until such Term Advances are
     paid in full, as follows: (1) first, 50% of such prepayment to be applied
     to

<PAGE>

     such installments in the order of maturity and (2) second, 50% of such
     prepayment to be applied to such installments pro rata."

     SECTION 1.02 Amendment to Acquisition Covenant. Section 5.02(h) of the
Credit Agreement is hereby amended by deleting the following text in subsection
5.02(h)(iii)(A):

     "75,000,000 (or, if Borrower Preferred Stock has converted to at least
     $200,000,000 of Borrower Common Stock (calculated at the conversion price
     of $27.50 per share of Borrower Common Stock rather than at the current
     market value of the Borrower Common Stock), $200,000,000); provided that
     the aggregate amount used in any year under this Section 5.02(h)(iii)(A)
     plus the amount borrowed under this Agreement to fund redemptions of
     Borrower Preferred Stock permitted under Section 5.02(e)(vi) and not
     repaid shall not exceed $275,000,000."

and inserting "$400,000,000" in lieu thereof.

     SECTION 1.03 Amendment to Debt Covenant. (a) Section 5.02(j) of the Credit
Agreement is hereby amended by adding the following new Section 5.02(j)(xiv):

          "(xiv) unsecured zero coupon convertible bonds issued in exchange for
     proceeds of not more than $500,000,000 and subordinated in right of
     payment to the payment in full of the obligations of the Borrower under
     this Agreement; provided that such bonds are issued on or before September
     30, 2001."

     (b) Such Section 5.02(j) is also amended to make conforming changes in the
punctuation by deleting "and" after the semicolon in subsection (xii), and
deleting the period at the end of subsection (xiii) and inserting "; and " in
lieu thereof.

                                   ARTICLE II

                         REPRESENTATIONS AND WARRANTIES

     SECTION 2.01 Representations and Warranties of the Borrower. The Borrower
represents and warrants as follows:

     (a) The Borrower is a corproation duly organized, validly existing and in
good standing under the laws of the State of Delaware.

                                       2

<PAGE>

     (b) The execution, delivery and performance by the Borrower of this
Amendment are within its corporate powers, have been duly authorized by all
necessary corporate action, and do not contravene the Borrower's charter or by-
laws.

     (c) No authorization or approval or other action by, and no notice to or
filing with, any governmental authority or regulatory body is required for the
due execution, delivery and performance by the Borrower of this Amendment.

     (d) This Amendment has been duly executed and delivered by the Borrower.
This Amendment is the legal, valid and binding obligation of the Borrower,
enforceable against the Borrower, in accordance with its terms, subject to
applicable bankruptcy, insolvency, reorganization, moratorium or similar laws
affecting the enforceability of creditors' rights generally and by general
principles of equity.

     (e) The representations and warranties contained in Section 4.01 of the
Credit Agreement are correct in all material respects on and as of the date
hereof, as though made on and as of the date hereof.

     (f) No event has occurred and is continuing which constitutes a Default.

                                  ARTICLE III

                                 MISCELLANEOUS

     SECTION 3.01 Governing Law. This Amendment shall be governed by, and
construed in accordance with, the laws of the State of New York, without regard
to the conflicts of law principles thereof.

     SECTION 3.02 Execution in Counterparts. This Amendment may be executed in
any number of counterparts and by any combination of the parties hereto in
separate counterparts, each of which counterparts shall be an original and all
of which taken together shall constitute one and the same instrument. Delivery
of an executed counterpart of a signature page to this Amendment by facsimile
shall be effective as delivery fo a manually executed counterpart of this
Amendment.

     SECTION 3.03 Effect on the Credit Agreement. Upon execution and delivery
of this Amendment, each reference in the Credit Agreement to this "Agreement",
"hereunder", "hereof", "herein", or words of like import shall mean and be a
reference to the Credit Agreement, as amended hereby and each reference to the
Credit Agreement in any Loan Document (as defined in the Credit

                                       3

<PAGE>

Agreement) shall mean and be a reference to the Credit Agreement, as amended
hereby. Except as expressly modified hereby, all of the terms and conditions of
the Credit Agreement shall remain unaltered and in full force and effect. This
Amendment is subject to the provisions of Section 8.01 of the Credit Agreement.

     Each of the undersigned has caused this Amendment to be executed by its
respective officer or officers thereunto duly authorized, as of the date first
written above.

BORROWER:                             LABORATORY CORPORATION OF
                                        AMERICA HOLDINGS

                                      By: /s/ Wesley R. Elingburg
                                         ---------------------------------------
                                         Name: Wesley R. Elingburg
                                         Title: Executive VP, CFO, and Treasurer

ADMINISTRATIVE                        CREDIT SUISSE FIRST BOSTON,
AGENT:                                  as Administrative Agent

                                      By: /s/ Karl M. Studer
                                         ---------------------------------------
                                         Name:  Karl M. Studer
                                         Title: Director

                                      By: /s/ Julia P. Kingsbury
                                         ---------------------------------------
                                         Name:  Julia P. Kingsbury
                                         Title: Vice President

                                       4

<PAGE>

                                      CREDIT SUISSE FIRST BOSTON

                                      By: /s/ Karl M. Studer
                                         ---------------------------------------
                                         Name:  Karl M. Studer
                                         Title: Director

                                      By: /s/ Roland Isler
                                         ---------------------------------------
                                         Name:  Roland Isler
                                         Title: Associate

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-5

<PAGE>

                                      BANK OF AMERICA , N.A.

                                      By: /s/ Philip S. Durand
                                         ---------------------------------------
                                         Name:  Philip S. Durand
                                         Title: Principal

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                               S-6

<PAGE>

                                      BANQUE NATIONALE DE PARIS

                                      By: /s/ Arnaud Collin du Bocage
                                         --------------------------------------
                                         Name:  Arnaud Collin du Bocage
                                         Title:

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

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-7

<PAGE>

                                      BAYERISCHE LANDESBANK GIROZENTRALE

                                      By: /s/ Alexander Kohnert
                                         ---------------------------------------
                                         Name:  Alexander Kohnert
                                         Title: First Vice President

                                      By: /s/ Wolfgang Kottmann
                                         ---------------------------------------
                                         Name:  Wolfgang Kottmann
                                         Title: Vice President

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-8

<PAGE>

                                      THE CHASE MANHATTAN BANK

                                      By: /s/ James W. Peterson
                                         ---------------------------------------
                                         Name:  James W. Peterson
                                         Title: Vice President

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-9

<PAGE>

                                      CREDIT LYONNAIS NEW YORK BRANCH

                                      By: /s/ Monique Benhamou
                                         ---------------------------------------
                                         Name:  Monique Benhamou
                                         Title: Vice President

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-10

<PAGE>

                                      DEUTSCHE BANK AG NEW YORK BRANCH
                                         and/or CAYMAN ISLANDS BRANCH

                                      By: /s/ Jean M. Hannigan
                                         ---------------------------------------
                                         Name:  Jean M. Hannigan
                                         Title:   Director

                                      By: /s/ Annette Walter
                                         ---------------------------------------
                                         Name:  Annette Walter
                                         Title: Associate

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-11

<PAGE>

                                      FIRST UNION NATIONAL BANK

                                      By: /s/ Douglas T. Davis
                                         ---------------------------------------
                                         Name:  Douglas T. Davis
                                         Title:  Senior Vice President

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-12

<PAGE>

                                      THE FUJI BANK, LTD. (NEW YORK BRANCH)

                                      By: /s/ Raymond Ventura
                                         ---------------------------------------
                                         Name:  Raymond Ventura
                                         Title: Vice President & Manager

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-13

<PAGE>

                                      UBS AG, Stamford Branch

                                      By: /s/ Wilfred V. Saint
                                        ----------------------------------------
                                         Name:  Wilfred V. Saint
                                         Title: Associate Director
                                                Banking Products Services US

                                      By: /s/ Robert P. Wagner
                                         ---------------------------------------
                                         Name:  Robert P. Wagner
                                         Title: Director

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-14

<PAGE>

                                      SOCIETE GENERALE

                                      By: /s/ Eric Bellaiche
                                         ---------------------------------------
                                         Name:  Eric Bellaiche
                                         Title: MD

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                     S-15

<PAGE>

                                      THE SUMITOMO BANK, LIMITED
                                          (NEW YORK BRANCH)

                                      By: /s/ Peter R. Knight
                                         ---------------------------------------
                                         Name:  Peter R. Knight
                                         Title: Sr. Vice President

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-16

<PAGE>

                                      WACHOVIA BANK, N.A., formerly known
                                         as Wachovia Bank of Georgia, N.A.

                                      By: /s/ Kathleen H. Reedy
                                         ---------------------------------------
                                         Name:  Kathleen H. Reedy
                                         Title: Senior Vice President

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-17

<PAGE>

                                      WESTDEUTSCHE LANDESBANK

                                      By: /s/ Richard J. Pearse
                                         ---------------------------------------
                                         Name:  Richard J. Pearse
                                         Title: Executive Director

                                      By: /s/ Lars Kickstein
                                         ---------------------------------------
                                         Name:  Lars Kickstein
                                         Title: Manager

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-18

<PAGE>

                                      COMMERZBANK AKTIENGESELLSCHAFT,
                                         Atlanta Agency

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

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

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-19

<PAGE>

                                      BBL INTERNATIONAL (U.K.) LIMITED

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

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

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-20

<PAGE>

                                      THE CHUO MITSUI TRUST AND BANKING
                                      CO., LIMITED

                                      By: /s/ Yoshiki Kiyono
                                         ---------------------------------------
                                         Name:  Yoshiki Kiyono
                                         Title: General Manager

                        [FIFTH AMENDMENT SIGNATURE PAGE]

                                      S-21

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