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                                                                      EXHIBIT 1



                           IRON MOUNTAIN INCORPORATED


                        5,000,000 SHARES OF COMMON STOCK


                             UNDERWRITING AGREEMENT


                                                                    MAY 11, 1999

BEAR, STEARNS & CO. INC.
WILLIAM BLAIR & COMPANY L.L.C.
PRUDENTIAL SECURITIES INCORPORATED
WASSERSTEIN PERELLA SECURITIES, INC.
         as Representatives of the several Underwriters
         named in Schedule I attached hereto

c/o Bear, Stearns & Co. Inc.
245 Park Avenue
New York, New York  10167

Dear Sirs:

                  Iron Mountain Incorporated (the "COMPANY"), a corporation
organized and existing under the laws of Delaware, proposes, subject to the
terms and conditions stated herein, to issue and sell to the several
Underwriters named in Schedule I hereto (the "UNDERWRITERS") an aggregate of
5,000,000 shares (the "FIRM SHARES") of its common stock, par value $.01 per
share (the "COMMON STOCK"), and, for the sole purpose of covering
over-allotments, if any, in connection with the sale of the Firm Shares, at the
option of the Underwriters, up to an additional 750,000 shares (the "ADDITIONAL
SHARES") of Common Stock. The Firm Shares and the Additional Shares are
collectively referred to herein as the "SHARES." The Shares are more fully
described in the Registration Statement referred to below.

                  1. REPRESENTATIONS AND WARRANTIES OF THE COMPANY. The Company
represents and warrants to the Underwriters that:

                  (a) The Company has filed with the Securities and Exchange
         Commission (the "COMMISSION") a registration statement, including a
         prospectus, on Form S-3 (No. 333-44185), for the registration of the
         Shares and certain other securities described therein that may be
         offered from time to time by the Company under the Securities Act of
         1933, as amended (the "SECURITIES ACT"). Such registration statement,
         including the prospectus, financial statements and schedules, exhibits
         and all other documents filed as a part thereof, as amended at the time
         of effectiveness of the registration statement, including any
         information deemed to be a part thereof as of the time of effectiveness
         pursuant to 

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         paragraph (b) of Rule 430A of the rules and regulations of
         the Commission under the Securities Act (the "REGULATIONS") or
         incorporated by reference therein, is herein called the "Registration
         Statement" and the prospectus, in the form first filed with the
         Commission pursuant to Rule 424(b) of the Regulations, is herein called
         the "Basic Prospectus." The term "Prospectus" means the Basic
         Prospectus as supplemented by the prospectus supplement dated the date
         hereof (the "PROSPECTUS SUPPLEMENT") specifically relating to the
         Shares, in the form first used to confirm sales of the Shares, filed
         pursuant to Rule 424 or Rule 430A under the Securities Act. The term
         "preliminary prospectus" as used herein means a preliminary prospectus
         supplement specifically relating to the Shares, together with the Basic
         Prospectus. Any reference herein to the Registration Statement, any
         preliminary prospectus or the Prospectus shall be deemed to refer to
         and include the documents incorporated by reference therein pursuant to
         Item 12 of Form S-3 which were filed under the Securities Exchange Act
         of 1934, as amended (the "EXCHANGE ACT"), on or before the effective
         date of the Registration Statement, the date of such preliminary
         prospectus or the date of the Prospectus, as the case may be, and any
         reference herein to the terms "amend," "amendment" or "supplement" with
         respect to the Registration Statement, any preliminary prospectus or
         the Prospectus shall be deemed to refer to and include (i) the filing
         of any document under the Exchange Act after the effective date of the
         Registration Statement, the date of such preliminary prospectus or the
         date of the Prospectus, as the case may be, which is incorporated
         therein by reference and (ii) any such document so filed.

                  (b) At the time of the effectiveness of the Registration
         Statement or the effectiveness of any post-effective amendment to the
         Registration Statement, when the Prospectus is first filed with the
         Commission pursuant to Rule 424(b) of the Regulations, when any
         supplement to or amendment of the Prospectus is filed with the
         Commission, when any document that was or will be incorporated by
         reference in the Registration Statement is or was filed under the
         Exchange Act, and at the First Closing Date and the Additional Closing
         Date, if any (as hereinafter respectively defined), the Registration
         Statement and the Prospectus and any amendments thereof and supplements
         thereto complied or will comply in all material respects with the
         applicable provisions of the Securities Act and the Regulations and the
         Exchange Act and the rules and regulations thereunder and did not or
         will not contain an untrue statement of a material fact and did not or
         will not omit to state any material fact required to be stated therein
         or necessary in order to make the statements therein (i) in the case of
         the Registration Statement, not misleading and (ii) in the case of the
         Prospectus, in light of the circumstances under which they were made,
         not misleading. When any related preliminary prospectus was first filed
         with the Commission (whether filed as part of the Registration
         Statement for the registration of the Shares or any amendment thereto
         or pursuant to Rule 424(b) of the Regulations) and when any amendment
         thereof or supplement thereto was first filed with the Commission, such
         preliminary prospectus and any amendments thereof and supplements
         thereto complied in all material respects with the applicable
         provisions of the Securities Act and the Regulations and the Exchange
         Act and the rules and regulations thereunder and did not contain an
         untrue statement of a material fact and did not omit to state any
         material fact required to be stated therein or necessary in order to

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         make the statements therein in light of the circumstances under which
         they were made not misleading. The Prospectus and any preliminary
         prospectus delivered to the Underwriters for use in connection with
         this offering was identical to the electronically transmitted copies
         thereof filed with the Commission pursuant to EDGAR, except to the
         extent permitted by Regulation S-T. No representation and warranty is
         made in this subsection (b), however, with respect to any information
         contained in or omitted from the Registration Statement or the
         Prospectus or any related preliminary prospectus or any amendment
         thereof or supplement thereto in reliance upon and in conformity with
         information furnished in writing to the Company by or on behalf of any
         Underwriter through the Representatives as herein stated expressly for
         use in connection with the preparation thereof.

                  (c) Subsequent to the respective dates as of which information
         is given in the Registration Statement and the Prospectus, except as
         set forth in the Registration Statement and the Prospectus, there has
         been no material adverse change or any development involving a
         prospective material adverse change in the business, prospects,
         properties, operations, condition (financial or other) or results of
         operations of the Company and its subsidiaries taken as a whole,
         whether or not arising from transactions in the ordinary course of
         business, and since the date of the latest balance sheet presented in
         the Registration Statement and the Prospectus, neither the Company nor
         any of its subsidiaries has incurred or undertaken any liabilities or
         obligations, direct or contingent, which are material to the Company
         and its subsidiaries taken as a whole, except for liabilities or
         obligations which are reflected in the Registration Statement and the
         Prospectus.

                  (d) The conditions for use of Form S-3, as set forth in the
         General Instructions thereto, have been satisfied by the Company. The
         Registration Statement has become effective; no stop order suspending
         the effectiveness of the Registration Statement is in effect, and no
         proceedings for such purpose are pending before or, to the knowledge of
         the Company, threatened by the Commission; and no order preventing or
         suspending the use of any preliminary prospectus has been issued by the
         Commission. Copies of such Registration Statement and amendments
         thereto (including documents incorporated by reference therein), the
         Basic Prospectus and all preliminary prospectuses contained therein
         have been delivered or made available to the Representatives.

                  (e) The documents incorporated or deemed to be incorporated by
         reference in the Prospectus, at the time they were or hereafter are
         filed with the Commission, complied and will comply in all material
         respects with the requirements of the Exchange Act and the rules and
         regulations of the Commission thereunder, and, when read together with
         the other information in the Prospectus, at the time the Registration
         Statement and any amendments thereto become effective and at the
         Closing Date (as hereinafter defined), will not contain any untrue
         statement of a material fact or omit to state a material fact required
         to be stated therein or necessary to make the statements therein, in
         the light of the circumstances under which they were made, not
         misleading.

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                  (f) The Company and each of its subsidiaries has been duly
         incorporated or formed, is validly existing as a corporation or limited
         liability company in good standing under the laws of its jurisdiction
         of incorporation or formation and has the corporate power and authority
         to carry on its business as it is currently being conducted and to own,
         lease and operate its properties, and each is duly qualified and is in
         good standing as a foreign corporation or limited liability company
         authorized to do business in each jurisdiction in which the nature of
         its business or its ownership or leasing of property requires such
         qualification, except where the failure to be so qualified would not
         have a material adverse effect (financial or otherwise) on the Company
         and its subsidiaries, taken as a whole.

                  (g) All of the outstanding shares of capital stock of, or
         other ownership interests in, each of the Company's subsidiaries have
         been duly authorized and validly issued and are fully paid and
         non-assessable, and are owned directly or indirectly by the Company
         (except for 12,789,246 shares representing 49.9% of the outstanding
         shares of capital stock of Britannia Data Management Limited ("BDM")),
         free and clear of any security interest, claim, lien, encumbrance or
         adverse interest of any nature, except for the security interests
         granted under the Second Amended and Restated Credit Agreement dated
         September 26, 1997 between the Company and The Chase Manhattan Bank, as
         Agent, as amended, or with respect to BDM, the security interests
         granted to The Governor and Company of the Bank of Scotland.

                  (h) This Agreement and the transactions contemplated herein
         have been duly and validly authorized by the Company, and this
         Agreement has been duly and validly executed and delivered by the
         Company and is a valid and binding agreement of the Company enforceable
         in accordance with its terms except as (i) rights to indemnity and
         contribution hereunder may be limited by applicable law, (ii) the
         enforceability thereof may be limited by bankruptcy, insolvency,
         fraudulent conveyance or similar laws affecting creditors' rights
         generally and (iii) rights of acceleration and the availability of
         equitable remedies may be limited by equitable principles of general
         applicability.

                  (i) The Shares have been duly authorized and, when issued and
         delivered to the Underwriters against payment therefor in accordance
         with the terms of this Agreement (and to the extent delivered in
         physical form, duly countersigned by the Company's Transfer Agent and
         Registrar), will be duly and validly issued and outstanding, fully paid
         and nonassessable and will not have been issued in violation of or be
         subject to any preemptive rights or similar rights to subscribe for or
         to purchase securities of the Company. No holder of securities of the
         Company has any right which has not been fully waived in writing to
         request or require the Company to register the offer or sale of any
         securities owned by such holder under the Securities Act in connection
         with the public offering contemplated by this Agreement.

                  (j) The authorized capital stock of the Company, including the
         Shares, conforms as to legal matters to the description thereof
         contained in the Registration Statement and the Prospectus.

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                  (k) The Company has caused BDM to enter into that certain
         Share Purchase Agreement For Shares In MAP S.A. among BDM, Carrick
         Invest and Mr. Richard Charbonneau, dated as of May 10, 1999 as may be
         amended from time to time (the "MEMOGARDE AGREEMENT"), which has been
         duly authorized, executed and delivered by BDM and, assuming the due
         authorization, execution and delivery by Carrick Invest and Mr. Richard
         Charbonneau, is a valid and binding agreement of BDM enforceable in
         accordance with its terms. The execution, delivery and performance of
         the Memogarde Agreement and compliance by BDM with all the provisions
         thereof and the consummation of the transactions contemplated thereby
         will not conflict with or constitute a breach of any of the terms or
         provisions of, or a default under, the charter or by-laws or comparable
         organizational documents of BDM or any of its subsidiaries or any
         agreement, indenture or other instrument to which it or any of its
         subsidiaries is a party or by which it or any of its subsidiaries or
         their respective property is bound, or violate or conflict with any
         laws, administrative regulations or rulings or court decrees applicable
         to BDM, any of its subsidiaries or their respective property.

                  (l) Neither the Company nor any of its subsidiaries is in
         violation of its respective charter or by-laws or comparable
         organizational documents or in default (and no condition exists which,
         with notice or lapse of time or both, would constitute a default) in
         the performance of any obligation, agreement or condition contained in
         any bond, debenture, note or any other evidence of indebtedness or in
         any other agreement, indenture or instrument material to the conduct of
         the business of the Company and its subsidiaries, taken as a whole, to
         which the Company or any of its subsidiaries is a party or by which it
         or any of its subsidiaries or their respective property is bound.

                  (m) The execution, delivery and performance of this Agreement
         and compliance by the Company with all the provisions hereof and the
         consummation of the transactions contemplated hereby will not require
         any consent, approval, authorization or other order of any court,
         regulatory body, administrative agency or other governmental body
         (except as such may be required under the Securities Act or under the
         securities or Blue Sky laws of the various states or jurisdictions of
         or outside the United States in connection with the offer and sale of
         the Shares), and will not conflict with or constitute a breach of any
         of the terms or provisions of, or a default under, or result in the
         creation or imposition of any lien, charge or encumbrance upon any
         property or assets of the Company or any of its subsidiaries pursuant
         to the terms of, the charter or by-laws or comparable organizational
         documents of the Company or any of its subsidiaries or any agreement,
         indenture or other instrument to which it or any of its subsidiaries is
         a party or by which it or any of its subsidiaries or their respective
         property is bound, or violate or conflict with any laws, administrative
         regulations or rulings or court decrees applicable to the Company, any
         of its subsidiaries or their respective property.

                  (n) Except as otherwise set forth in the Prospectus, there are
         no material legal or governmental proceedings pending to which the
         Company or any of its subsidiaries is a party or to which any of their
         respective property is subject, and, to the best of the Company's
         knowledge, no such proceedings are threatened or contemplated.

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                  (o) Neither the Company nor any of its subsidiaries is
         currently in violation of any foreign, federal, state or local law or
         regulation relating to the protection of human health and safety, the
         environment or hazardous or toxic substances or wastes, pollutants or
         contaminants ("ENVIRONMENTAL LAWS"), nor any federal or state law
         relating to discrimination in the hiring, promotion or pay of employees
         nor any applicable federal or state wages and hours laws, nor any
         provisions of the Employee Retirement Income Security Act of 1974, as
         amended, or the rules and regulations promulgated thereunder, which in
         each case might result in any material adverse change in the business,
         prospects, financial condition or results of operations of the Company
         and its subsidiaries, taken as a whole.

                  (p) The Company and each of its subsidiaries has such permits,
         licenses, franchises and authorizations of governmental or regulatory
         authorities ("PERMITS"), including, without limitation, under any
         applicable Environmental Laws, as are necessary to own, lease and
         operate its respective properties and to conduct its respective
         business, except for such permits which would not result in any
         material adverse change in the prospects, financial condition or
         results of operations of the Company and its subsidiaries, taken as a
         whole; the Company and each of its subsidiaries has fulfilled and
         performed all of its material obligations with respect to such permits
         and no event has occurred which allows, or after notice or lapse of
         time would allow, revocation or termination thereof which might result
         in any material adverse change in the business, prospects, financial
         condition or results of operations of the Company and its subsidiaries,
         taken as a whole; and, except as described in the Prospectus, such
         permits contain no restrictions that materially interfere with the
         business or operations of the Company or any of its subsidiaries as
         currently conducted.

                  (q) In the ordinary course of its business, when the Company
         or any of its subsidiaries acquires a fee interest in a parcel of real
         property, the Company conducts a review (which is a Phase I Study or a
         review of a recent Phase I Study prepared on behalf of the seller or
         any predecessor owner of such property), as it relates to such real
         property, of the effect of Environmental Laws on the business,
         operations and properties of the Company and its subsidiaries, in the
         course of which it attempts to identify and evaluate associated costs
         and liabilities, if any (including, without limitation, any capital or
         operating expenditures required for clean-up, closure of properties or
         compliance with Environmental Laws or any permit, any related
         constraints on operating activities and any potential liabilities to
         third parties). In the ordinary course of its business, when the
         Company or any of its subsidiaries enters into a long-term real
         property lease, the Company conducts a review (which may or may not
         include a Phase I Study), as it relates to such real property, of the
         effect of Environmental Laws on the business, operations and properties
         of the Company and its subsidiaries, in the course of which it attempts
         to identify and evaluate associated costs and liabilities, if any
         (including, without limitation, any capital or operating expenditures
         required for clean-up, closure of properties or compliance with
         Environmental Laws or any permit, any related constraints on operating
         activities and any potential liabilities to third parties). On the
         basis of such review, the Company has reasonably concluded that such
         associated costs and liabilities would not,

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         singly or in the aggregate, have a material adverse effect (financial
         or otherwise) on the Company and its subsidiaries, taken as a whole.

                  (r) Except as otherwise set forth in the Prospectus or such as
         are not material to the business, prospects, financial condition or
         results of operations of the Company and its subsidiaries, taken as a
         whole, the Company and each of its subsidiaries has good and marketable
         title, free and clear of all liens, claims, encumbrances and
         restrictions except liens for taxes not yet due and payable, to all
         property and assets described in the Prospectus as being owned by it.
         All leases to which the Company or any of its subsidiaries is a party
         are valid and binding and no default by the Company or any of its
         subsidiaries, or to the knowledge of the Company or any of its
         subsidiaries, by any other party, has occurred or is continuing
         thereunder, which might result in any material adverse change in the
         business, prospects, financial condition or results of operations of
         the Company and its subsidiaries, taken as a whole, and the Company and
         its subsidiaries enjoy peaceful and undisturbed possession under all
         such leases to which any of them is a party as lessee with such
         exceptions as do not materially interfere with the use made or proposed
         to be made by the Company or such subsidiary.

                  (s) The Company and each of its subsidiaries maintains, with
         insurers of recognized standing, reasonably adequate insurance against
         property and casualty loss, general liability, business interruption
         and such other losses and risks, in each case, in such amounts as are
         prudent and customary in the business in which they are engaged.

                  (t) Arthur Andersen LLP are independent public accountants
         with respect to the Company within the meaning of the Securities Act.

                  (u) The financial statements, together with related schedules
         and notes forming part of the Registration Statement and the Prospectus
         (and any amendment or supplement thereto), present fairly the
         consolidated financial position, results of operations and changes in
         financial position of the Company and its subsidiaries on the basis
         stated in the Registration Statement and the Prospectus at the
         respective dates or for the respective periods to which they apply;
         such statements and related schedules and notes have been prepared in
         accordance with generally accepted accounting principles consistently
         applied throughout the periods involved, except as disclosed therein;
         and the other financial and statistical information and data set forth
         in the Registration Statement and the Prospectus (and any amendment or
         supplement thereto) is, to the Company's knowledge, in all material
         respects, accurately presented and prepared on a basis reasonably
         consistent with the books and records of the Company.

                  (v) Neither the Company nor any of its affiliates does
         business with the government of Cuba or with any person or affiliate
         located in Cuba within the meaning of Section 517.075, Florida Statutes
         (Chapter 92-198, Laws of Florida).

                  (w) The Company has an authorized, issued and outstanding
         capitalization as set forth in the Registration Statement and the
         Prospectus and all of the outstanding shares of capital stock of the
         Company have been duly authorized and validly issued and 

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         are fully paid and nonassessable and were not issued in violation
         of or subject to any preemptive rights.

                  (x) There are no outstanding subscriptions, rights, warrants,
         options, calls, convertible securities, commitments of sale or liens
         related to or entitling any person to purchase or otherwise to acquire
         any shares of the capital stock of, or other ownership interest in, the
         Company or any subsidiary thereof except as otherwise disclosed in the
         Prospectus.

                  (y) The Company has disclosed in the Prospectus, or otherwise
         disclosed to the Representatives in writing, any business relationships
         or related party transactions of the type that is required to be
         disclosed by Item 404 of Regulation S-K of the Commission.

                  (z) There is (i) no significant unfair labor practice
         complaint pending against the Company or any of its subsidiaries or, to
         the best knowledge of the Company, threatened against any of them,
         before the National Labor Relations Board or any state or local labor
         relations board, and no significant grievance or arbitration proceeding
         arising out of or under any collective bargaining agreement is pending
         against the Company or any of its subsidiaries or, to the best
         knowledge of the Company, threatened against any of them, and (ii) no
         significant strike, labor dispute, slowdown or stoppage pending against
         the Company or any of its subsidiaries or, to the best knowledge of the
         Company, threatened against it or any of its subsidiaries except for
         such actions specified in clause (i) or (ii) above, which, singly or in
         the aggregate, could not reasonably be expected to have a material
         adverse effect (financial or otherwise) on the Company and its
         subsidiaries, taken as a whole.

                  (aa) The Company and each of its subsidiaries maintains a
         system of internal accounting controls sufficient to provide reasonable
         assurance that (i) transactions are executed in accordance with
         management's general or specific authorizations, (ii) transactions are
         recorded as necessary to permit preparation of financial statements in
         conformity with generally accepted accounting principles and to
         maintain asset accountability, (iii) access to assets is permitted only
         in accordance with management's general or specific authorization and
         (iv) the recorded accountability for assets is compared with the
         existing assets at reasonable intervals and appropriate action is taken
         with respect to any differences.

                  (bb) All material tax returns required to be filed by the
         Company and each of its subsidiaries in any jurisdiction have been
         filed, other than those filings being contested in good faith, and all
         material taxes, including withholding taxes, penalties and interest,
         assessments, fees and other charges due pursuant to such returns or
         pursuant to any assessment received by the Company or any of its
         subsidiaries have been paid, other than those being contested in good
         faith and for which adequate reserves have been provided.

                  (cc) The Company and its subsidiaries own or possess, or can
         acquire on reasonable terms, all material patents, patent applications,
         trademarks, service marks,

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         trade names, licenses, copyrights and proprietary or other confidential
         information currently employed by them in connection with their
         respective businesses, and neither the Company nor any such subsidiary
         has received any notice of infringement of or conflict with asserted
         rights of any third party with respect to any of the foregoing which,
         singly or in the aggregate, if the subject of an unfavorable decision,
         ruling or finding, would result in any material adverse change in the
         business, prospects, financial condition or results of operations of
         the Company and its subsidiaries, taken as a whole, except as described
         in or contemplated by the Prospectus.

                  (dd) The Company is not, and upon consummation of the
         transactions contemplated by this Agreement will not be, an "investment
         company" or a company "controlled" by an "investment company" within
         the meaning of the Investment Company Act of 1940, as amended (the
         "INVESTMENT COMPANY ACT"), or be subject to registration under the
         Investment Company Act.

                  (ee) The Company and each of its affiliates has not taken and
         will not take, directly or indirectly, any action which is designed to
         or which constitutes or which might reasonably be expected to cause or
         result in the stabilization or manipulation of the price of any
         security of the Company to facilitate the sale or resale of the Shares
         and neither the Company nor any of its affiliated purchasers (as
         defined in Rule 100 of Regulation M under the Exchange Act) will take
         any action prohibited by Regulation M under the Exchange Act.

                  2. PURCHASE, SALE AND DELIVERY OF THE SHARES. (a) Subject to
the terms and conditions herein set forth and on the basis of the
representations, warranties, covenants and agreements herein contained, the
Company agrees to sell 5,000,000 Firm Shares to the Underwriters, and each
Underwriter agrees, severally, but not jointly, to purchase from the Company the
number of Firm Shares, set forth opposite the name of such Underwriter on
Schedule I hereto, plus any additional number of Firm Shares which such
Underwriter may become obligated to purchase pursuant to the provisions of
Section 9 hereof.

                  Payment of the purchase price for, and delivery of, the Firm
Shares, shall be made at the offices of Latham & Watkins, 885 Third Avenue, New
York, New York 10022 at 9:30 a.m. (New York time) on the third business day
(unless postponed in accordance with this Agreement or, if the Firm Shares are
priced, as contemplated by Rule 15c6-1(c) under the Exchange Act, after 4:30
p.m., New York time, the fourth business day) following the date of this
Agreement or at such other time or on such other date but not later than ten
business days after such date as shall be mutually agreed in writing between the
Company and Bear, Stearns & Co. Inc. on behalf of the Representatives (the time
and date of such payment and delivery being herein called the "FIRST CLOSING
DATE"). The Company shall deliver or cause to be delivered the Firm Shares in
such denominations and registered in such names as Bear, Stearns & Co. Inc. on
behalf of the Representatives may request in writing at least two full business
days prior to the First Closing Date. Payment shall be made to the Company on
the First Closing Date by certified or official bank check or checks drawn in
federal funds or same day funds payable to the order of the Company or by wire
transfer in same day funds to the Company, against delivery to Bear, Stearns &
Co. Inc. on behalf of Representatives, on behalf of the Underwriters, of the
Firm

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Shares. The Company will permit the Representatives to examine and package
such certificates for delivery at least one full business day prior to the First
Closing Date. For purposes of this Section 2, the term "business day" shall mean
any day except Saturday, Sunday and any day which shall be a legal holiday or a
day on which banking institutions are authorized or required by law or
government action to close in the State of New York.

                  (b) In addition, the Company has granted to the Underwriters,
solely for the purpose of covering over-allotments, if any, in the sale of Firm
Shares, an option (the "OPTION") to purchase all or any portion of the
Additional Shares, in pro rata proportion with respect to the Firm Shares sold
by the Company hereunder, exercisable on or before the thirtieth day following
the date of this Agreement, by written notice by Bear, Stearns & Co. Inc. on
behalf of the Representatives to the Company. Such notice shall set forth the
aggregate number of Additional Shares as to which the Option is being exercised
and the date and time, as reasonably determined by Bear, Stearns & Co. Inc. on
behalf of the Representatives, when the Additional Shares are to be delivered
(such date and time being herein sometimes referred to as the "ADDITIONAL
CLOSING DATE;" the First Closing Date and the Additional Closing Date may be
referred to herein as the "CLOSING DATE"); provided, however, that the
Additional Closing Date shall not be earlier than the First Closing Date or, if
the Additional Closing Date is to occur on a date other than the First Closing
Date, earlier than the third business day after the date on which the Option
shall have been exercised nor later than the eighth business day after the date
on which the Option shall have been exercised (unless such time and date are
postponed in accordance with the provisions of this Agreement). Certificates for
the Additional Shares shall be registered in such name or names and in such
authorized denominations as Bear, Stearns & Co. Inc. on behalf of the
Representatives may request in writing at least two full business days prior to
the Additional Closing Date. The Company will permit the Representatives to
examine and package such certificates for delivery at least one full business
day prior to the Additional Closing Date.

                  Payment of the purchase price for, and delivery of, the
Additional Shares shall be made at the offices of Latham & Watkins, 885 Third
Avenue, New York, New York 10022 at 9:30 a.m. (New York time) on the Additional
Closing Date (unless postponed in accordance with this Agreement). Payment for
the Additional Shares shall be made to the Company by certified or official bank
check or checks in federal funds or similar same day funds payable to the order
of the Company or by wire transfer in same day funds to the Company, against
delivery to Bear, Stearns & Co. Inc. on behalf of the Representatives, on behalf
of the Underwriters, of the Additional Shares.

                  (c) The price to be paid by the Underwriters for both the Firm
         Shares and the Additional Shares shall be $26.67 per Share.

                  3. OFFERING. Upon your authorization of the release of the
Shares, the several Underwriters propose to offer the Shares for sale to the
public initially upon the terms set forth in the Prospectus.

                  4. AGREEMENTS OF THE COMPANY. The Company agrees with the
Underwriters that:

                                       10

<PAGE>


                  (a) Immediately following the execution of this Agreement, the
         Company will prepare a Prospectus Supplement setting forth the number
         of Shares covered thereby and their terms not otherwise specified in
         the Basic Prospectus, the price at which the Shares are to be purchased
         by the Underwriters from the Company, and such other information as the
         Representatives and the Company deem appropriate in connection with the
         offering of the Shares; and the Company will promptly transmit copies
         of the Prospectus Supplement to the Commission for filing pursuant to
         Rule 424(b) of the Regulations and will furnish to the Representatives
         as many copies of the Prospectus (including such Prospectus Supplement)
         as they shall reasonably request.

                  (b) The Company will make no further amendment or supplement
         to the Registration Statement or Prospectus, except as permitted
         herein; and, if at any time when a prospectus relating to the Shares is
         required to be delivered under the Securities Act, any event shall have
         occurred as a result of which the Prospectus as then amended and
         supplemented would, in the judgment of Bear, Stearns & Co. Inc. on
         behalf of the Representatives, include an untrue statement of a
         material fact or omit to state any material fact necessary in order to
         make the statements therein, in the light of the circumstances under
         which they were made when such Prospectus is delivered, not misleading,
         or, if for any other reason it shall be necessary during such same
         period to amend or supplement the Registration Statement or Prospectus
         in order to comply with the Securities Act or the Regulations or to
         file under the Exchange Act so as to comply therewith any document
         incorporated by reference in the Registration Statement or the
         Prospectus or in any amendment thereof or supplement thereto, the
         Company will notify the Representatives, afford the Representatives a
         reasonable opportunity to comment on any such proposed amendment or
         supplement, upon the Representatives' request, prepare and furnish
         without charge to each Underwriter and to any dealer in securities as
         many copies as the Representatives may from time to time reasonably
         request of an amended Prospectus or a supplement to the Prospectus,
         which will correct such statement or omission or effect such
         compliance, and use its best efforts to have any amendment to the
         Registration Statement declared effective as soon as possible.

                  (c) During the period in which a prospectus is required to be
         delivered under the Securities Act or Exchange Act in connection with
         sales of the Shares by an underwriter or dealer, the Company will
         advise the Representatives promptly (i) of receipt by the Company of
         any notification with respect to the suspension of the qualification of
         the Shares for sale in any jurisdiction or the initiation or threat of
         any proceeding for that purpose; (ii) of any downgrading in the rating
         accorded any of the securities of the Company by any "nationally
         recognized statistical rating organization" (as defined for purposes of
         Rule 436(g) under the Securities Act), or any public announcement that
         any such organization has under surveillance or review its rating of
         any such securities (other than an announcement with positive
         implications of a possible upgrading, and no implication of a possible
         downgrading of such rating) as soon as the Company learns of any such
         downgrading or public announcement; (iii) after it receives notice of
         the issuance by the Commission of any stop order or of any order
         preventing or suspending the use of any preliminary prospectus or the
         Prospectus; or (iv) of any request by the Commission for the amending
         or supplementing of the Registration Statement and

                                       11

<PAGE>


         any preliminary prospectus or the Prospectus or for additional
         information; and, in the event of the issuance of any stop order or of
         any order preventing or suspending the use of any preliminary
         prospectus or the Prospectus or suspending any such qualification, the
         Company will use its reasonable efforts to obtain its withdrawal.

                  (d) The Company will furnish the Representatives with such
         number of manually signed copies of the Registration Statement,
         including all exhibits, amendments and documents incorporated by
         reference therein, as reasonably requested by the Representatives and,
         during the period in which a prospectus is required to be delivered
         under the Securities Act or Exchange Act in connection with sales of
         the Shares by an underwriter or dealer, to furnish the Underwriters
         copies of any preliminary prospectus and Prospectus, and all amendments
         and supplements, in such quantities as the Representatives may from
         time to time reasonably request.

                  (e) The Company will make generally available (within the
         meaning of Section 11(a) of the Securities Act) to its security holders
         and to the Underwriters as soon as practicable, but in any event not
         later than 45 days after the end of its fiscal quarter in which the
         first anniversary date of the date of the Prospectus occurs, an
         earnings statement of the Company and its subsidiaries (which need not
         be audited) complying with the provisions of Rule 158 of the Regulation
         covering a period of at least twelve consecutive months beginning after
         the effective date of the Registration Statement.

                  (f) Prior to the date hereof, the Company has applied for
         listing of these Shares on the New York Stock Exchange and will use its
         best efforts to complete that listing, subject only to official notice
         of issuance, prior to the First Closing Date.

                  (g) The Company will not (and will cause its affiliates not
         to) take, directly or indirectly, any action which is designed to or
         which constitutes or which might reasonably be expected to cause or
         result in the stabilization or manipulation of the price of any
         security of the Company to facilitate the sale or resale of the Shares
         and neither the Company nor any of its affiliated purchasers (as
         defined in Rule 100 of Regulation M under the Exchange Act) will take
         any action prohibited by Regulation M under the Exchange Act.

                  (h) The Company will apply the net proceeds of the issue and
         sale of the Shares to be sold by the Company as set forth under the
         caption "Use of Proceeds" in the Prospectus.

                  (i) During a period of three years from the date of the
         Prospectus, the Company will furnish to Bear, Stearns & Co. Inc. on
         behalf of the Underwriters as soon as available a copy of each report
         or other publicly available information of the Company mailed to the
         security holders of the Company or filed with the Commission and such
         other publicly available information concerning the Company and its
         subsidiaries as the Underwriters may reasonably request.

                                       12

<PAGE>


                  (j) The Company will use its best efforts to do and perform,
         or cause to be done or performed, all things required or necessary to
         be done and performed under this Agreement by the Company prior to the
         Closing Date, and to satisfy all conditions precedent to the delivery
         of the Shares.

                  (k) The Company will endeavor in good faith, in cooperation
         with the Underwriters, at or prior to the time of the date of the
         Prospectus, to qualify, to the extent necessary, the Shares for
         offering and sale under the securities laws relating to the offering or
         sale of the Shares of such jurisdictions within the United States of
         America as the Underwriters may designate and to maintain such
         qualification in effect for so long as required for the distribution
         thereof; except that in no event shall the Company be obligated in
         connection therewith to qualify as a foreign corporation or to execute
         a general consent to service of process.

                  (l) During the period of 90 days from the date of the
         Prospectus, the Company will not, directly or indirectly, without the
         prior written consent of Bear, Stearns & Co. Inc., offer, sell,
         contract to sell, swap, make any short sale, pledge, establish an open
         "put equivalent position" within the meaning of Rule 16a-1(h) under the
         Exchange Act, grant any option to purchase or otherwise dispose (or
         publicly announce the intention to do any of the foregoing) of, or file
         or announce the filing of any registration statement in connection with
         the offer or sale of, any shares of Common Stock of the Company (or any
         securities convertible into, exercisable for or exchangeable for shares
         of Common Stock of the Company), and the Company will obtain the
         undertaking of each of the directors, executive officers and certain
         other officers listed in the "Management" section of the Prospectus
         Supplement and the former stockholders of Data Base, Inc. that are a
         party to the Stock Purchase Agreement with the Company, dated as of
         February 28, 1999, as may be amended from time to time (the "DATA BASE
         AGREEMENT"), not to engage in any of the aforementioned transactions on
         their own behalf. Notwithstanding the foregoing, during such period the
         Company may (i) issue Common Stock upon the exercise of presently
         outstanding stock options and issue options to purchase shares of
         Common Stock pursuant to any of its stock option plans existing on the
         date of this Agreement, and (ii) enter into and perform acquisition
         agreements that may obligate the Company to issue up to an aggregate
         1,000,000 shares of Common Stock pursuant thereto and issue shares of
         Common Stock pursuant to such agreements, so long as the persons
         receiving or to receive such shares in accordance with this clause (ii)
         agree in writing to be bound to the same degree that Company is bound
         pursuant to this Section 4(l) for any period remaining under the
         Company's agreement hereunder.

                  (m) During the period when the Prospectus is required to be
         delivered under the Securities Act or the Exchange Act, the Company
         will file all documents required to be filed with the Commission
         pursuant to Section 13, 14 or 15 of the Exchange Act within the time
         periods required by the Exchange Act and the rules and regulations
         thereunder.

                  5. EXPENSES. The Company will pay all costs and expenses
incident to the performance of its obligations under this Agreement, whether or
not the transactions

                                       13
<PAGE>


contemplated herein are consummated or this Agreement is terminated pursuant to
Sections 9 or 11 hereof, including all costs and expenses incident to (a) the
printing or other production of documents with respect to the transactions,
including any costs of printing and filing with the Commission of any
preliminary prospectus and the Prospectus and the printing and distribution of
any underwriting documents, including this Agreement, (b) all arrangements
relating to the delivery to the Underwriters of copies of the foregoing and
related documents, (c) the fees and disbursements of the counsel, the
accountants and any other experts or advisors retained by the Company, (d) the
costs incident to the issuance, transfer and delivery of the Shares to the
Underwriters, including any stamp, value-added or transfer or other taxes
payable thereon, (e) the preparation, issuance and delivery to the Underwriters
of any stock certificates evidencing the Shares, (f) the qualification of the
Shares under state or foreign securities or "blue sky" laws, including the costs
of printing and mailing a preliminary and final "Blue Sky Survey" and the filing
fees and reasonable fees and disbursements of counsel for the Underwriters
relating thereto (if any), (g) all expenses and listing fees in connection with
the listing of the Shares on the New York Stock Exchange, (h) the costs and
charges (including fees and disbursements of counsel) of the transfer agent and
registrar, and (i) any meetings with prospective investors in the Shares (other
than as shall have been specifically approved by the Representatives to be paid
for by the Underwriters); PROVIDED, HOWEVER, that the Underwriters will
reimburse the Company for certain mutually agreed upon costs and expenses
incident to the Company's offering of the Shares.

                  6. CONDITIONS TO UNDERWRITERS' OBLIGATIONS. The several
obligations of the Underwriters to purchase the Firm Shares under this Agreement
are subject to the satisfaction of each of the following conditions:

                  (a) The Registration Statement shall continue to be effective
         as of the First Closing Date; the Prospectus shall have been filed with
         the Commission pursuant to Rule 424(b) within the applicable time
         period prescribed for such filing by the Regulations; no stop order
         suspending the Registration Statement or the Prospectus or any part
         thereof shall have been issued and no proceeding for that purpose shall
         have been initiated or threatened by the Commission; and all requests
         for additional information on the part of the Commission shall have
         been complied with to the reasonable satisfaction of Bear, Stearns &
         Co. Inc. on behalf of the Representatives.

                  (b) All the representations and warranties of the Company
         contained in this Agreement shall be true and correct on the First
         Closing Date with the same force and effect as if made on and as of the
         First Closing Date.

                  (c) (i) Since the date of the latest balance sheet included in
         the Prospectus, there shall not have been any material adverse change,
         or any development involving a prospective material adverse change, in
         the business, prospects, financial condition or results of operations
         of the Company and its subsidiaries taken as a whole, whether or not
         arising in the ordinary course of business, except as otherwise
         described in the Prospectus, (ii) since the date of the latest balance
         sheet included in the Prospectus, there shall not have been any
         material change, or any development involving a prospective material
         adverse change, in the capital stock or in the long-term debt of the
         Company from that set forth in the Prospectus, (iii) the Company and
         its subsidiaries shall have no


                                       14
<PAGE>


         liability or obligation, direct or contingent, which is material to the
         Company and its subsidiaries, taken as a whole, other than those
         described in the Prospectus and (iv) on the First Closing Date you
         shall have received a certificate dated the First Closing Date, signed
         by C. Richard Reese, in his capacity as Chairman of the Board and Chief
         Executive Officer, and by John F. Kenny, Jr., in his capacity as
         Executive Vice President and Chief Financial Officer of the Company,
         confirming the matters set forth in paragraphs (b), (c) and (i) of this
         Section 6.

                  (d) The Underwriters shall have received on the First Closing
         Date an opinion (satisfactory to the Underwriters and counsel for the
         Underwriters), dated the First Closing Date, of Sullivan & Worcester
         LLP, counsel for the Company, to the effect that:

                           (i) each of the Company and its subsidiaries set
                  forth on Schedule II hereto (the "SIGNIFICANT SUBSIDIARIES")
                  has been duly incorporated or formed, is validly existing as a
                  corporation or limited liability company in good standing
                  under the laws of its jurisdiction of incorporation or
                  formation and has the corporate or limited liability company
                  power and authority required to carry on its business as it is
                  currently being conducted and to own, lease and operate its
                  properties;

                           (ii) each of the Company and the Significant
                  Subsidiaries is duly qualified and is in good standing as a
                  foreign corporation or limited liability company authorized to
                  do business in each jurisdiction in which the nature of its
                  business or its ownership or leasing of property requires such
                  qualification, except where the failure to be so qualified
                  would not have a material adverse effect on the Company and
                  its subsidiaries, taken as a whole;

                           (iii) all of the outstanding shares of capital stock
                  of, or other ownership interests in, each of the Company's
                  Significant Subsidiaries have been duly and validly authorized
                  and issued and are fully paid and non-assessable, and except
                  as set forth in the Prospectus are owned beneficially by the
                  Company, free and clear of any perfected security interest,
                  or, to the knowledge of such counsel, any other security
                  interest, claim, lien, encumbrance or adverse interest of any
                  nature;

                           (iv) the Company has an authorized, issued and
                  outstanding capitalization as set forth in the Registration
                  Statement and the Prospectus and all of the outstanding shares
                  of capital stock have been duly authorized and validly issued
                  and are fully paid and nonassessable and were not issued in
                  violation of or subject to any preemptive or similar rights to
                  subscribe for or to purchase securities of the Company
                  contained in the Amended and Restated Certificate of
                  Incorporation or the Amended and Restated By-Laws of the
                  Company or in any agreements of the Company of which such
                  counsel has knowledge. The Firm Shares have been duly and
                  validly authorized and, when issued and delivered to and paid
                  for by the Underwriters in accordance with this Agreement,
                  will be duly and validly issued, fully paid and nonassessable
                  and will not have been issued in violation of or subject to
                  any preemptive rights or similar rights to subscribe for or

                                       15

<PAGE>


                  to purchase securities of the Company contained in the Amended
                  and Restated Certificate of Incorporation or the Amended and
                  Restated By-Laws of the Company or in any agreements of the
                  Company of which such counsel has knowledge. To such counsel's
                  knowledge, no holder of securities of the Company has any
                  right which has not been fully waived in writing to request or
                  require the Company to register the offer or sale of any
                  securities owned by such holder under the Securities Act in
                  connection with the public offering contemplated by this
                  Agreement. The Common Stock and the Firm Shares conform to the
                  descriptions thereof contained in the Registration Statement
                  and the Prospectus;

                           (v) this Agreement has been duly authorized, executed
                  and delivered by the Company and is a valid and binding
                  agreement of the Company enforceable in accordance with its
                  terms except as (A) rights to indemnity and contribution
                  hereunder may be limited by applicable law, (B) enforceability
                  thereof may be limited by bankruptcy, insolvency, fraudulent
                  conveyance or similar laws affecting creditors' rights
                  generally and (C) the availability of equitable remedies may
                  be limited by equitable principles of general applicability;

                           (vi) the statements under the captions "Description
                  of Capital Stock" and "Underwriting" in the Prospectus, as
                  amended or supplemented, insofar as such statements constitute
                  a summary of legal matters, documents or proceedings referred
                  to therein, fairly present the information called for with
                  respect to such legal matters, documents and proceedings;

                           (vii) to such counsel's knowledge, neither the
                  Company nor any of its subsidiaries is in violation of its
                  respective charter or by-laws or comparable organizational
                  documents and, to such counsel's knowledge, neither the
                  Company nor any of its subsidiaries is in default in the
                  performance of any obligation, agreement or condition
                  contained in the Memogarde Agreement, except as such defaults
                  would not, singly or in the aggregate, result in a material
                  adverse change in the business, prospects, financial condition
                  or results of operations of the Company or any of its
                  subsidiaries, taken as a whole;

                           (viii) The execution, delivery and performance of
                  this Agreement and compliance by the Company with all the
                  provisions hereof, and the consummation of the transactions
                  contemplated hereby will not require any consent, approval,
                  authorization or other order of any court, regulatory body,
                  administrative agency or other governmental body (except as
                  such may be required under the Securities Act and under the
                  securities or Blue Sky laws of the various states or
                  jurisdictions of or outside the United States in connection
                  with the offer and sale of the Shares), and will not conflict
                  with or constitute a breach of any of the terms or provisions
                  of, or a default under, the charter or by-laws or comparable
                  organizational documents of the Company or any of its
                  Significant Subsidiaries or any agreement, indenture or other
                  instrument known to such counsel to which it or any of its
                  Significant Subsidiaries is a party or by which it or any of
                  its Significant

                                       16

<PAGE>


                  Subsidiaries or their respective property is bound, or violate
                  or conflict with any laws, administrative regulations or
                  rulings or court decrees applicable to the Company, any of its
                  subsidiaries or their respective property;

                           (ix) such counsel does not know (A) of any legal or
                  governmental proceeding pending or threatened to which the
                  Company or any of its subsidiaries is a party or to which any
                  of their respective property is subject which is required to
                  be described in the Prospectus and is not so described, or (B)
                  of any contract or other document which is required to be
                  described in the Prospectus and is not so described;

                           (x) to such counsel's knowledge, (A) neither the
                  Company nor any of its subsidiaries is in violation of any
                  federal or state law or regulation relating to the storage,
                  handling or transportation of hazardous or toxic materials,
                  (B) the Company and its subsidiaries have received all
                  permits, licenses or other approvals required of them under
                  applicable federal and state environmental laws and
                  regulations to conduct their respective businesses as
                  described in the Prospectus and (C) the Company and each of
                  its subsidiaries is in compliance with all terms and
                  conditions of any such permit, license or approval, except any
                  such violation of law or regulation, failure to receive
                  required permits, licenses or other approvals or failure to
                  comply with the terms and conditions of such permits, licenses
                  or approvals as would not, singly or in the aggregate, result
                  in a material adverse change in the business, prospects,
                  financial condition or results of operations of the Company
                  and its subsidiaries, taken as a whole;

                           (xi) the Company is not, and upon consummation of the
                  transactions contemplated by this Agreement will not be, an
                  "investment company" or a company "controlled" by an
                  "investment company" within the meaning of the Investment
                  Company Act or subject to registration under the Investment
                  Company Act;

                           (xii) such counsel believes that (except for
                  financial statements, schedules and other financial and
                  statistical information contained therein) (1) the
                  Registration Statement (or any documents incorporated by
                  reference therein), does not contain and, at the time the
                  Registration Statement became effective, did not contain any
                  untrue statement of a material fact or omit or omitted to
                  state a material fact required to be stated therein or
                  necessary to make the statements therein, in light of the
                  circumstances under which they were made, not misleading, and
                  (2) the Prospectus, as amended or supplemented, if applicable,
                  (or any documents incorporated by reference therein), as of
                  its date and at the date of such opinion, did not and does not
                  contain any untrue statement of a material fact or omit to
                  state a material fact necessary in order to make the
                  statements therein, in the light of the circumstances under
                  which they were made, not misleading;

                           (xiii) The Registration Statement has become
                  effective under the Act, and, to the best knowledge of such
                  counsel, no stop order suspending the 

                                       17

<PAGE>


                  effectiveness of the Registration Statement has been issued
                  and no proceedings therefor have been initiated or threatened
                  by the Commission and all filings required by Rule 424(b) of
                  the Regulations have been made;

                           (xiv) The Registration Statement, the Prospectus and
                  each amendment thereof or supplement thereto (except the
                  financial statements, schedules and other financial and
                  statistical information contained or incorporated by reference
                  therein), as of their respective effective or issue dates,
                  complied as to form in all material respects with the
                  requirements of the Securities Act and the Regulations;

                           (xv) Each document filed pursuant to the Exchange Act
                  and incorporated by reference in the Registration Statement
                  and the Prospectus or any amendment thereof or supplement
                  thereto (except the financial statements, schedules and other
                  financial and statistical information contained or
                  incorporated by reference therein) when they were filed with
                  the Commission complied as to form in all material respects
                  with the requirements of the Securities Act or the Exchange
                  Act, as applicable, and the respective rules and regulations
                  of the Commission thereunder; and

                           (xvi) The Common Stock currently outstanding is
                  approved for listing on, and the Shares to be sold under this
                  Agreement to the Underwriters are duly authorized for listing,
                  on the New York Stock Exchange.

                           In giving such opinion with respect to the matters
                  covered by clause (xii) such counsel may state that their
                  opinion and belief are based upon their participation in the
                  preparation of the Prospectus and any amendments or
                  supplements thereto and review and discussion of the contents
                  thereof, but are without independent check or verification
                  except as specified. Notwithstanding the foregoing, the
                  opinion with respect to the matters covered by clause (i),
                  (ii) and (iii), relating to BDM and its subsidiaries, may be
                  delivered by Eversheds or other U.K. counsel reasonably
                  satisfactory to the Underwriters.

                  (e) The Underwriters shall have received on the First Closing
         Date an opinion (satisfactory to Bear, Stearns & Co. Inc. on behalf of
         the Underwriters and counsel for the Underwriters), dated the First
         Closing Date, of Garry B. Watzke, Esq., general counsel for the
         Company, as to the matters referred to in clauses (vi), (viii), (ix)
         and (xii) of the foregoing paragraph (d) and as to the following
         additional matters:

                           (i) to such counsel's knowledge, neither the Company
                  nor any of its subsidiaries is in violation of its respective
                  charter or by-laws or comparable organizational documents and,
                  to such counsel's knowledge, neither the Company nor any of
                  its subsidiaries is in default in the performance of any
                  obligation, agreement or condition contained in any bond,
                  debenture, note or other evidence of indebtedness or in any
                  other agreement, indenture or instrument material to the
                  conduct of the business of the Company and its subsidiaries,
                  taken as a whole, to 

                                       18

<PAGE>


                  which the Company or any of its subsidiaries is a party or by
                  which it or any of its subsidiaries or their respective
                  properties are bound;

                           (ii) all leases to which the Company or any of its
                  subsidiaries is a party relating to real property in
                  Massachusetts or California are valid and binding and no
                  default has occurred or is continuing thereunder, which might
                  result in any material adverse change in the business,
                  prospects, financial condition or results of operations of the
                  Company and its subsidiaries taken as a whole, and the Company
                  and its subsidiaries enjoy peaceful and undisturbed possession
                  under all such leases to which any of them is a party as
                  lessee with such exceptions as do not materially interfere
                  with the use made by the Company or such subsidiary; and

                           (iii) to such counsel's knowledge, the Company and
                  each of its subsidiaries has such permits, licenses,
                  franchises and authorizations of governmental or regulatory
                  authorities ("PERMITS"), including, without limitation, under
                  any applicable Environmental Laws, as are necessary to own,
                  lease and operate its respective properties and to conduct its
                  respective business in the manner described in the Prospectus;
                  to such counsel's knowledge without having conducted any
                  independent investigation, the Company and each of its
                  subsidiaries has fulfilled and performed all of its material
                  obligations with respect to such permits and no event has
                  occurred which allows, or after notice or lapse of time would
                  allow, revocation or termination thereof or would result in
                  any other material impairment of the rights of the holder of
                  any such permit, except in each case as would not, singly or
                  in the aggregate, have a material adverse effect (financial or
                  otherwise) on the Company and its subsidiaries, taken as a
                  whole and, except as described in the Prospectus, such permits
                  contain no restrictions that materially interfere with the
                  business or operations of the Company or any of its
                  subsidiaries as currently conducted.

                  In giving such opinion with respect to the matters covered by
clause (xii) of the foregoing paragraph (d) such counsel may state that his
opinion and belief are based upon his participation in the preparation of the
Prospectus and any amendments or supplements thereto and review and discussion
of the contents thereof, but are without independent check or verification
except as specified.

                  (f) The opinions of Sullivan & Worcester LLP and Garry B.
         Watzke described in paragraphs (d) and (e) above, respectively, shall
         be rendered to the Underwriters at the request of the Company and shall
         so state therein.

                  (g) The Underwriters shall have received on the First Closing
         Date an opinion, dated the First Closing Date, of Latham & Watkins,
         counsel for the Underwriters, as to such matters as the Underwriters
         shall reasonably request.

                  (h) The Underwriters shall have received a letter or letters
         on and as of the date of this Agreement (each, an "INITIAL LETTER"), in
         form and substance satisfactory to the Representatives, from Arthur
         Andersen LLP (with respect to Iron Mountain Incorporated,

                                       19

<PAGE>


         Midwest Records Management, Sloan Vaults, Inc. and Affiliates and
         InterMation, Inc.), Abbott, Stringham & Lynch (with respect to Records
         Retention/FileSafe, L.P.), Robson Rhodes (with respect to BDM), Ernst &
         Young LLP (with respect to Arcus Technology Services, Inc., Arcus
         Group, Inc. and HIMSCORP, Inc. and Subsidiaries), Moss Adams LLP (with
         respect to Data Base, Inc. and Affiliate), Brach, Neal, Daney & Spence,
         LLP (with respect to First American Records Management, Inc.) and
         Carbis Walker & Associates, LLP (with respect to National Underground
         Storage, Inc.), each independent public accountants, with respect to
         the financial statements and certain financial information contained in
         the Registration Statement and the Prospectus and a letter or letters
         on and as of the First Closing Date, in form and substance satisfactory
         to the Representatives, from Arthur Andersen LLP, Abbott, Stringham &
         Lynch, Robson Rhodes, Ernst & Young LLP, Moss Adams LLP, Brach, Neal,
         Daney & Spence, LLP, and Carbis Walker & Associates, LLP confirming the
         information contained in the initial letter or letters provided by such
         accountants.

                  (i) The Company shall not have failed at or prior to the First
         Closing Date to perform or comply with any of the agreements herein
         contained and required to be performed or complied with by the Company
         at or prior to the First Closing Date.

                  (j) Prior to the First Closing Date, the Company shall have
         furnished to the Representatives such further information, certificates
         and documents as the Representatives may reasonably request.

                  (k) The Company shall have delivered to you prior to the date
         of this Agreement the agreements executed in accordance with Section
         4(l) hereof.

                  (l) At the First Closing Date, the Shares shall have been
         approved for listing on the New York Stock Exchange, subject only to
         official notice of issuance and evidence of satisfactory distribution.

                  If any of the conditions specified in this Section 6 shall not
have been fulfilled when and as required by this Agreement, or if any of the
certificates, opinions, written statements or letters furnished to the
Representatives or to Underwriters' Counsel pursuant to this Section 6 shall not
be in all material respects reasonably satisfactory in form and substance to the
Representatives and to Underwriters' Counsel, all obligations of the
Underwriters hereunder may be canceled by the Underwriters at, or at any time
prior to, the First Closing Date and the obligations of the Underwriters to
purchase the Additional Shares may be canceled by the Underwriters at, or at any
time prior to, the Additional Closing Date. Notice of such cancellation shall be
given to the Company in writing, or by telephone, telex or telegraph, confirmed
in writing.

                  The respective obligations of the several Underwriters to
purchase and pay for any Additional Shares shall be subject, in their
discretion, to each of the foregoing conditions to purchase the Firm Shares,
except that all references to the Firm Shares and the First Closing Date shall
be deemed to refer to such Additional Shares and the Additional Closing Date,
respectively.

                                       20

<PAGE>


                  7. INDEMNIFICATION. (a) The Company agrees to indemnify and
hold harmless each Underwriter and each person, if any, who controls any
Underwriter within the meaning of Section 15 of the Securities Act or Section
20(a) of the Exchange Act, against any and all losses, liabilities, claims,
damages and expenses whatsoever as incurred (including, but not limited to,
reasonable attorneys' fees and any and all reasonable expenses whatsoever
incurred in investigating, preparing or defending against any litigation,
commenced or threatened, or any claim whatsoever, and any and all amounts paid
in settlement of any claim or litigation), joint or several, to which they or
any of them may become subject under the Securities Act, the Exchange Act or
otherwise, insofar as such losses, liabilities, claims, damages or expenses (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 the Registration
Statement, as originally filed or any amendment thereof, or any related
preliminary prospectus or the Prospectus or in any amendment thereof or
supplement thereto, or arise out of or are based upon the omission or alleged
omission to state therein a material fact necessary to make the statements
therein, in the light of the circumstances in which they were made, not
misleading; provided, however, that the Company shall not be liable in any such
case to the extent, but only to the extent, that any such loss, liability,
claim, damage or expense arises out of or is based upon any such untrue
statement or omission, or alleged untrue statement or omission, made therein in
reliance upon and in conformity with written information furnished to the
Company by, or on behalf of, any Underwriter through the Representatives
expressly for use therein. This indemnity obligation will be in addition to any
liability which the Company may otherwise have, including under this Agreement.

                  (b) Each Underwriter, severally, but not jointly, agrees to
indemnify and hold harmless the Company, each of the directors of the Company,
each of the officers of the Company, and each other person, if any, who controls
the Company within the meaning of Section 15 of the Securities Act or Section
20(a) of the Exchange Act, against any losses, liabilities, claims, damages and
expenses whatsoever as incurred (including but not limited to attorneys' fees
and any and all reasonable expenses whatsoever incurred in investigating,
preparing or defending against any litigation, commenced or threatened, or any
claim whatsoever, and any and all amounts paid in settlement of any claim or
litigation), jointly or severally, to which they or any of them may become
subject under the Securities Act, the Exchange Act or otherwise, insofar as such
losses, liabilities, claims, damages or expenses (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 the Prospectus or in any amendment thereof or
supplement thereto, or arise out of or are based upon the omission or alleged
omission to state therein a material fact necessary to make the statements
therein, in the light of the circumstances in which they were made, not
misleading, in each case to the extent, but only to the extent, that any such
loss, liability, claim, damage or expense arises out of or is based upon any
such untrue statement or omission, or alleged untrue statement or omission, made
therein in reliance upon and in conformity with written information furnished to
the Company by, or on behalf of, any Underwriter through the Representatives
expressly for use therein; PROVIDED, HOWEVER, that in no case shall any
Underwriter be liable or responsible for any amount in excess of the
underwriting discount applicable to the Shares purchased by such Underwriter
hereunder. The Company acknowledges that (i) the statements set forth in the
last paragraph of the inside front cover of the

                                       21

<PAGE>


Prospectus and (ii) the names of the Underwriters listed in the table within,
and the second to last paragraph of, the Underwriting Section of the Prospectus
constitute the only information furnished to the Company in writing by, or on
behalf of, any Underwriter expressly for use in the Prospectus or in any
amendment thereof or supplement thereto.

                  (c) Promptly after receipt by an indemnified party under
subsection (a) or (b) above of notice of the commencement of any action, such
indemnified party shall, if a claim in respect thereof is to be made against the
indemnifying party under such subsection, notify each party against whom
indemnification is to be sought in writing of the commencement thereof (but the
failure so to notify an indemnifying party shall not relieve it from any
liability which it may have under this Section 7, or otherwise). In case any
such action is brought against any indemnified party, and such indemnified party
notifies an indemnifying party of the commencement thereof, the indemnifying
party will be entitled to participate in the defense of such action, and to the
extent such indemnifying party may elect by written notice delivered to the
indemnified party promptly after receiving the aforesaid notice from such
indemnified party to assume the defense thereof with counsel satisfactory to
such indemnified party. Notwithstanding the foregoing, the indemnified party or
parties shall have the right to employ its or their own counsel in any such
case, but the fees and expenses of such counsel shall be at the expense of such
indemnified party or parties unless (i) the employment of such counsel shall
have been authorized in writing by one of the indemnifying parties in connection
with the defense of such action, (ii) the indemnifying parties shall not have
employed counsel to have charge of the defense of such action within a
reasonable time after notice of commencement of the action, or (iii) such
indemnified party or parties shall have reasonably concluded that there may be
defenses available to it or them which are different from or additional to those
available to one or all of the indemnifying parties (in which case the
indemnifying parties shall not have the right to direct the defense of such
action on behalf of the indemnified party or parties), in any of which events
such fees and expenses shall be borne by the indemnifying parties (it being
understood, however, that the indemnifying party shall not be liable in any one
action or separate but substantially similar or related actions in the same
jurisdiction for the expenses of more than one separate counsel and one
additional local counsel). Anything in this subsection to the contrary
notwithstanding, an indemnifying party shall not be liable for any settlement of
any claim or action effected without its written consent (which consent may not
be unreasonably withheld). No indemnifying party shall, without the prior
written consent of the indemnified party, effect any settlement of any pending
or threatened proceeding in respect of which any indemnified party is or could
have been a party and indemnity could have been sought hereunder by such
indemnified party, unless such settlement includes an unconditional release of
such indemnified party from all liability or claims that are the subject matter
of such proceeding.

                  8. CONTRIBUTION. In order to provide for contribution in
circumstances in which the indemnification provided for in Section 7 hereof is
for any reason held to be unavailable from any indemnifying party or is
insufficient to hold harmless a party indemnified thereunder, the Company and
the Underwriters shall contribute to the aggregate losses, claims, damages,
liabilities and expenses of the nature contemplated by such indemnification
provision (including any investigation, legal and other expenses incurred in
connection with, and any amount paid in settlement of, any action, suit or
proceeding or any claims asserted, but after deducting any contribution received
from persons who may also be liable for contribution,

                                       22

<PAGE>


including officers and directors of the Company and persons who control the
Company within the meaning of Section 15 of the Securities Act or Section 20(a)
of the Exchange Act) to which the Company, on the one hand, and one or more of
the Underwriters, on the other hand, may be subject as incurred in such
proportions as is appropriate to reflect the relative benefits received by the
Company, on the one hand, and the Underwriters, on the other hand, from the
offering of the Shares or, if such allocation is not permitted by applicable law
or indemnification is not available as a result of the indemnifying party not
having received notice as provided in Section 7 hereof, in such proportion as is
appropriate to reflect not only the relative benefits referred to above but also
the relative fault of the Company, on the one hand, and the Underwriters, on the
other hand, in connection with the statements or omissions which resulted in
such losses, claims, damages, liabilities or expenses, as well as any other
relevant equitable considerations. The relative benefits received by the
Company, on the one hand, and the Underwriters, on the other hand, shall be
deemed to be in the same proportion as (x) the total proceeds from the offering
of the Shares (net of discounts to the Underwriters but before deducting
expenses) received by the Company and (y) the total discounts and commissions
received by the Underwriters bear to the total price to the public of the
Shares, in each case as set forth in the table on the cover page of the
Prospectus. The relative fault of the Company on the one hand, and of the
Underwriters, on the other hand, shall be determined by reference to, among
other things, whether the untrue or alleged untrue statement of a material fact
or the omission or alleged omission to state a material fact relates to
information supplied by the Company on the one hand, or the Underwriters, on the
other hand, and the parties' relative intent, knowledge, access to information
and opportunity to correct or prevent such statement or omission. The Company
and the Underwriters agree that it would not be just and equitable if
contribution pursuant to this Section 8 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 Section 8, 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. Notwithstanding the provisions of this Section 8, no
Underwriter shall be required to contribute any amount in excess of the amount
by which the total price at which the Shares purchased by it were offered to
investors exceeds the amount of any damages that such Underwriter has otherwise
been required to pay by reason of such untrue or alleged untrue statement or
omission or alleged omission. For purposes of this Section 8, each person, if
any, who controls any Underwriter within the meaning of Section 15 of the
Securities Act or Section 20(a) of the Exchange Act shall have the same rights
to contribution as the Underwriters, and each person, if any, who controls the
Company within the meaning of Section 15 of the Securities Act or Section 20(a)
of the Exchange Act and each officer and each director of the Company shall have
the same rights to contribution as the Company. 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, notify each party or
parties from whom contribution may be sought, but the omission to so notify such
party or parties shall not relieve the party or parties from whom contribution
may be sought from any obligation it or they may have under this Section 8 or
otherwise, except to the extent that it has been prejudiced in any material
respect by the omission to so notify. No party shall be liable for contribution
with respect to any action or claim settled without its consent (which consent
may not be unreasonably withheld).

                                       23

<PAGE>


                  9. DEFAULT BY AN UNDERWRITER.

                  (a) If one or more of the Underwriters shall fail at each
applicable Closing Date to purchase the Shares which it or they are obligated to
purchase under this Agreement (the "DEFAULTED SHARES") and such Defaulted Shares
do not exceed in the aggregate 10% of the aggregate principal amount of the
Shares, then each non-defaulting Underwriter shall purchase an aggregate amount
of the Defaulted Shares equal to the proportion that the aggregate principal
amounts of Shares to be purchased by such Underwriter as set forth opposite such
Underwriter's name on Schedule I hereto bears to the aggregate principal amount
of Shares to be purchased by all non-defaulting Underwriters.

                  (b) Notwithstanding the foregoing, if the Defaulted Shares
equal or exceed in the aggregate 10% of the aggregate principal amount of the
Shares, then the non-defaulting Underwriters shall have the right, within 48
hours after the Closing Date, to make arrangements for one or more of such
non-defaulting Underwriters to purchase all, but not less than all, of the
Defaulted Shares in such amounts as may be agreed upon among such non-defaulting
Underwriters and upon the terms herein set forth; PROVIDED that if the
non-defaulting Underwriters shall not have completed such arrangements within
such 48-hour period, then this Agreement shall terminate without liability on
the part of the non-defaulting Underwriters or the Company.

                  No action taken pursuant to this Section 9 shall relieve any
defaulting Underwriter from liability in respect of its default.

                  In the event of any such default which does not result in a
termination of this Agreement, any of the non-defaulting Underwriters or the
Company shall have the right to postpone the Closing Date for a period not
exceeding seven days in order to effect any required changes in the Prospectus
or in any other documents or arrangements.

                  10. SURVIVAL OF REPRESENTATIONS AND AGREEMENTS. All
representations and warranties, covenants and agreements of the Underwriters or
the Company contained in this Agreement, including, without limitation, the
agreements contained in Sections 4 and 5, the indemnity agreements contained in
Section 7 and the contribution agreements contained in Section 8, shall remain
operative and in full force and effect regardless of any investigation made by
or on behalf of the Underwriters or any controlling person thereof or by or on
behalf of the Company, any of its officers and directors or any controlling
person thereof, and shall survive delivery of and payment for the Shares to and
by the Underwriters. The representations contained in Section 1 and the
agreements contained in Sections 2 (to the extent provided in Section 9), 5, 7
and 8 and this Section 10 shall survive the termination of this Agreement,
including termination pursuant to Section 9 or 11.

                  11. TERMINATION. (a) The Representatives shall have the right
to terminate this Agreement at any time prior to the Closing Date:

                  (i) if any domestic or international event or act or
         occurrence has materially disrupted, or in the Representatives' sole
         opinion will in the immediate future materially

                                       24

<PAGE>


         disrupt, the market for the Company's securities or the United States
         or international securities markets in general;

                  (ii) if trading on the New York Stock Exchange, the American
         Stock Exchange or the National Association of Securities Dealers
         Automated Quotation System shall have been suspended or materially
         limited;

                  (iii) if a banking moratorium has been declared by any United
         States federal or New York State authority or if any new restriction
         materially adversely affecting the distribution of the Shares shall
         have become effective;

                  (iv) if the United States becomes engaged in hostilities or
         there is an escalation of hostilities involving the United States or
         there is a declaration of a national emergency or war by the United
         States; or

                  (v) if there shall have been any other change in political,
         financial or economic conditions, if the effect of such event in the
         sole judgment of the Representatives is to make it impracticable or
         inadvisable to proceed with the offering, sale and delivery of the
         Shares on the terms contemplated by the Prospectus.

                  (b) Any notice of termination pursuant to this Section 11
shall be made to the Company by telephone, telex or telegraph, confirmed in
writing by letter.

                  (c) If this Agreement shall be terminated pursuant to any of
the provisions hereof (otherwise than pursuant to Section 9(b) or 11(a)), or if
the sale of the Shares provided for herein is not consummated because any
condition to the obligations of the Underwriters set forth herein is not
satisfied or because of any refusal, inability or failure on the part of the
Company to perform any agreement herein or comply with the provision hereof, the
Company will, subject to demand by the Representatives, reimburse the
Underwriters for all out-of-pocket expenses (including the fees and expenses of
their counsel), incurred by the Underwriters in connection herewith.

                  12. NOTICE. All communications hereunder, except as may be
otherwise specifically provided herein, shall be in writing and, if sent to any
Underwriter, shall be mailed, delivered, telecopied, telexed or telegraphed and
confirmed in writing, to such Underwriter, c/o Bear, Stearns & Co. Inc., 245
Park Avenue, New York, New York 10167 Attention: Christopher Churchill; with a
copy to Latham & Watkins, 885 Third Avenue, New York, New York 10022, Attention:
Robert A. Zuccaro; if sent to the Company, shall be mailed, delivered,
telecopied, telexed or telegraphed and confirmed in writing to Iron Mountain
Incorporated, 745 Atlantic Avenue, 10th Floor, Boston, Massachusetts 02111,
Attention: Chief Executive Officer; with a copy to Sullivan & Worcester LLP, One
Post Office Square, Boston, Massachusetts 02109, Attention: William J. Curry.

                  13. CONSENT TO JURISDICTION; WAIVER OF IMMUNITIES. (a) The 
Company:

                           (i) irrevocably submits to the jurisdiction of any
                  New York State or federal court sitting in New York City and
                  any appellate court from any thereof in

                                       25

<PAGE>


                  any action or proceeding arising out of or relating to this
                  Agreement or any other document delivered hereunder;

                           (ii) irrevocably agrees that all claims in respect of
                  any such action or proceeding may be heard and determined in
                  such New York State court or in such federal court; and

                           (iii) irrevocably waives, to the fullest extent
                  permitted by law, the defense of an inconvenient forum to the
                  maintenance of such action or proceeding and irrevocably
                  consents, to the fullest extent permitted by law, to service
                  of process of any of the aforementioned courts in any such
                  action or proceeding by the mailing of copies thereof by
                  registered or certified mail, postage prepaid, to the Company
                  at its address as provided in Section 12 of this Agreement,
                  such service to become effective five days after such mailing;

                  (b) Nothing in this Section 13 shall affect the right of any
         person to serve legal process in any other manner permitted by law or
         affect the right of any person to bring any action or proceeding
         against the Company or its properties in the courts of other
         jurisdictions.

                  14. PARTIES. This Agreement shall inure solely to the benefit
of, and shall be binding upon, the Underwriters, the Company and the controlling
persons, directors, officers, employees and agents referred to in Sections 7 and
8, and their respective successors and assigns, and no other person shall have
or be construed to have any legal or equitable right, remedy or claim under or
in respect of or by virtue of this Agreement or any provision herein contained.
The term "successors and assigns" shall not include a purchaser, in its capacity
as such, of Shares from the Underwriters.

                  15. GOVERNING LAW. This Agreement shall be governed by and
construed in accordance with the laws of the State of New York for contracts
made and to be fully performed in such state without regard to the conflict of
law principles thereof.

                  16. COUNTERPARTS. This Agreement may be executed and delivered
(including by facsimile transmission) in one or more counterparts, and by the
different parties hereto in separate counterparts, each of which when executed
and delivered shall be deemed to be an original but all of which taken together
shall constitute one and the same agreement.

                                     26

<PAGE>


                  If the foregoing is in accordance with your understanding of
our agreement, please sign and return to the Company a counterpart hereof,
whereupon this instrument, along with all counterparts, will become a binding
agreement between the Underwriters and the Company in accordance with its terms.

                             Very truly yours,

                             IRON MOUNTAIN INCORPORATED


                             By:    / S /  C. RICHARD REESE
                                    -----------------------
                                    Name:   C. Richard Reese
                                    Title:  Chairman and Chief Executive Officer


Accepted as of the date first above written:

BEAR, STEARNS & CO. INC.
WILLIAM BLAIR & COMPANY L.L.C.
PRUDENTIAL SECURITIES INCORPORATED
WASSERSTEIN PERELLA SECURITIES, INC.

By:  / S /  STEPHEN PARISH
     ----------------------
     Name:    Stephen Parish
     Title:   Senior Managing Director
     On behalf of themselves and the other
     Underwriters named on Schedule I hereto

<PAGE>


                                   SCHEDULE I
<TABLE>
<CAPTION>

                                                                                      Number of Additional Shares to
                                                   Total Number of Firm Shares To     be Purchased if Maximum Option
              Name of Underwriter                           Be Purchased                       is Exercised
              -------------------                  -----------------------------      ------------------------------
<S>                                                           <C>                                  <C> 
Bear, Stearns & Co., Inc.                                     2,760,000                            414,000

William Blair & Company L.L.C.                                1,150,000                            172,500

Prudential Securities Incorporated                              460,000                             69,000

Wasserstein Perella Securities, Inc.                            230,000                             34,500

Allen & Company Incorporated                                    100,000                             15,000

BancBoston Robertson Stephens Inc.                              100,000                             15,000

CJS Securities, Inc.                                            100,000                             15,000

Jefferies & Company, Inc.                                       100,000                             15,000
                                                              ---------                            -------
                                                              ---------                            -------
                             Total                            5,000,000                            750,000

</TABLE>


<PAGE>


                                   SCHEDULE II

                        LIST OF SIGNIFICANT SUBSIDIARIES
<TABLE>
<CAPTION>


                               Name                  State or Jurisdiction of
-------------------------------------------------          Incorporation
                                                    -------------------------
<S>                                                       <C> 
Iron Mountain Records Management, Inc.                       Delaware

Iron Mountain of Maryland LLC                                Delaware

Iron Mountain/Safesite, Inc.                                 Delaware

Arcus Data Security, Inc.                                    Delaware

Arcus Staffing Resources, Inc.                               Delaware

Iron Mountain/National Underground Storage, Inc.             Delaware

Criterion Atlantic Property, Inc.                            Delaware

Britannia Data Management Limited                         United Kingdom

</TABLE>