UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A
(RULE 14a-101)
INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No.           )

IRON MOUNTAIN INCORPORATED

745 Atlantic Avenue
Boston, Massachusetts 02111

NOTICE OF 20032004 ANNUAL MEETING OF SHAREHOLDERS
TO BE HELD ON MAY 22, 200327, 2004

To the Shareholders of
    IRON MOUNTAIN INCORPORATED:

        Iron Mountain Incorporated will hold its 20032004 Annual Meeting of Shareholders at the offices of Sullivan & Worcester LLP, One Post Office Square, 23rd21st Floor, Boston, Massachusetts, on May 22, 200327, 2004 at 10:00 a.m. local time for the following purposes:

1.

To elect three Class IIIthe directors of Iron Mountain Incorporated for a three-yearone-year term or until their successors are elected and qualified;



2.

To approve an amendment to Iron Mountain's Amended and Restated Articles of Incorporation to increase the adoptionnumber of theauthorized shares of Iron Mountain Incorporated 2003 EmployeeMountain's Common Stock, Purchase Plan;par value $.01 per share, from 150,000,000 to 200,000,000;



3.

To approve the adoption ofan amendment to the Iron Mountain Incorporated 2003 Senior Executive2002 Stock Incentive Program;Plan to increase the number of shares of Common Stock authorized for issuance thereunder from 1,352,543 to 3,352,543; and



4.

To transact such other business as may properly come before the Annual Meeting.

        Attached to this notice is a Proxy Statement relating to the proposals to be considered at the Annual Meeting. The Board of Directors has fixed the close of business on April 1, 20035, 2004 as the record date for the determination of shareholders entitled to receive notice of and to vote at the Annual Meeting or at any adjournment or postponement thereof. In the event that the Annual Meeting is adjourned for at least 15 days due to the absence of a quorum, those shareholders entitled to vote who attend the adjourned meeting, although otherwise less than a quorum, shall constitute a quorum for the purpose of acting upon any matter set forth in this notice.notice except with regard to Item 3 as set forth in the accompanying proxy statement.

        Your vote is important regardless of the number of shares you own. The Company requests that you complete, sign, date and return the enclosed proxy card without delay in the enclosed postage-paid return envelope, even if you now plan to attend the Annual Meeting. You may revoke your proxy at any time prior to its exercise by delivering written notice or another duly executed proxy bearing a later date to the Secretary of the Company, or by attending the Annual Meeting and voting in person.

        All shareholders are cordially invited to attend the Annual Meeting.

By order of the Board of Directors,

GARRY B. WATZKE,B.WATZKE,Secretary

Boston, Massachusetts
April 17, 200322, 2004

IRON MOUNTAIN INCORPORATED

745 ATLANTIC AVENUE
BOSTON, MASSACHUSETTS 02111

PROXY STATEMENT
FOR THE ANNUAL MEETING OF SHAREHOLDERS

To be held on May 22, 200327, 2004

GENERAL INFORMATION

        This Proxy Statement is furnished in connection with the solicitation of proxies by the Board of Directors (the "Board") of Iron Mountain Incorporated ("Iron Mountain" or the "Company") for use at the Annual Meeting of Shareholders (the "Annual Meeting") to be held on May 22, 200327, 2004 or at any adjournment or postponement thereof.

        The Company's Annual Report to Shareholders for the year ended December 31, 20022003 is being mailed to shareholders with the mailing of this Proxy Statement on or about April 17, 2003.22, 2004.

        Iron Mountain will bear all costs of solicitation of proxies. Brokers, banks, custodians and other fiduciaries will be requested to forward proxy soliciting materialmaterials to the beneficial owners of shares held of record by such persons, and the Company will reimburse them for their reasonable out-of-pocket expenses incurred in connection with the distribution of such proxy materials. Solicitation of proxies by mail may be supplemented by telephone, telecopier or personal solicitation by directors, officers or other regular employees of the Company (who will not receive any additional compensation for any solicitation of proxies), as well as the firm of Georgeson Shareholder, which has been retained by the Company to assist in the solicitation for a fee of approximately $5,850$7,500 plus reasonable expenses.

Revocability of Proxies

        Any shareholder giving a proxy in the enclosed form has the power to revoke it at any time before it is exercised. You may revoke your proxy by delivering to the Secretary of the Company at the address given above a written notice of revocation or another duly executed proxy bearing a later date. You may also revoke your proxy by attending the Annual Meeting and voting in person.

Record Date, Voting and Share Ownership

        Iron Mountain's common stock, $0.01 par value per share (the "Common Stock"), is the only class of voting securities outstanding and entitled to vote at the Annual Meeting. As of the close of business on April 1, 2003,5, 2004, the record date for the determination of shareholders entitled to notice of and to vote at the Annual Meeting, 85,184,73485,843,184 shares of Common Stock were outstanding and entitled to vote. Each share is entitled to one vote on each matter.

        The presence at the Annual Meeting, in person or by proxy, of shareholders entitled to cast at least a majority of the votes that all shareholders are entitled to cast at the Annual Meeting will constitute a quorum. Shares represented by a properly signed and returned proxy will be treated as present at the Annual Meeting for purposes of determining a quorum, without regard to whether the proxy is marked as casting a vote or abstaining. Shares represented by "broker non-votes" will not be treated as present for purposes of determining a quorum; however, shares voted by a broker on any issue other than a procedural motion will be considered present for all quorum purposes, even if the shares are not voted on every matter. A broker non-vote occurs on an item when a broker identified as the record holder of shares is not permitted to vote on that item without instruction from the beneficial owner of the shares and no instruction has been received.

        A proxy in the enclosed form, if received in time for voting and not revoked, will be voted at the Annual Meeting in accordance with the instructions contained therein. Where a choice is not so specified, the shares represented by the proxy will be counted:

•

"For" the election of the nominees for director listed herein;

•

"For" the approval and adoption of the Iron Mountain Incorporated 2003 Employee Stock Purchase Planamendment to the Company's Amended and Restated Articles of Incorporation (the "ESPP""Charter Amendment"); and



•

"For" the approval and adoption of the amendment to the Iron Mountain Incorporated 2003 Senior Executive2002 Stock Incentive ProgramPlan (the "SEIP""Plan Amendment").

        Abstentions and broker non-votes will not be counted as votes cast and, therefore, will not affect the election of the directors, the adoption of the ESPPCharter Amendment or the adoption of the SEIP.Plan Amendment.

        Our website address is included several times in this proxy statement as a textual reference only and the information in the website is not incorporated by reference into this proxy statement.

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ITEM 1

ELECTION OF DIRECTORS

        The Board has unanimously adopted resolutions approving an amendment to Sections 3.1(c) and (d) of our Bylaws to declassify the Board. Section 3.1(c) of our Bylaws previously provided that the Board be divided into three classes, as nearly equal in number as reasonably possible, with members of each class serving three-year terms. The amendment provides for the annual election of all directors in the manner described below. The Board currently consists of nine directors. There are three classesWhile the amendment does not change the present number of directors, who serve for a three-year term and are elected on a staggered basis, one classthe Board has separately determined to reduce the number of directors standing for election each year. The termto eight effective as of the Class III directors, Kent P. Dauten, Arthur D. Little and C. Richard Reese, will expire at the2004 Annual Meeting. The termBoard will retain the authority to change that number and to fill any vacancies or newly created directorships.

        Classified or staggered boards have been widely adopted and have a long history in corporate law. Proponents of classified boards assert they promote the independence of directors because directors elected for multi-year terms are less subject to outside influence. Proponents of a staggered system for the election of directors also believe it provides continuity and stability in the management of the Class Ibusiness and affairs of a company because a majority of directors Clarke H. Bailey, Constantin R. Bodenalways have prior experience as directors of the Company. Proponents further assert that classified boards may enhance shareholder value by forcing an entity seeking control of a target company to initiate arms-length discussions with the board of a target company because the entity is unable to replace the entire board in a single election.

        On the other hand, some investors view classified boards as having the effect of reducing the accountability of directors to shareholders because classified boards limit the ability of shareholders to evaluate and Eugene B. Doggett,elect all directors on an annual basis. The election of directors is a primary means for shareholders to influence corporate governance policies and to hold management accountable for implementing those policies. In addition, opponents of classified boards assert that a staggered structure for the election of directors may discourage proxy contests in which shareholders have an opportunity to vote for a competing slate of nominees and therefore may erode shareholder value.

        Our Nominating and Governance Committee and Board have carefully considered the advantages and disadvantages of maintaining a classified board structure, and have concluded it is an appropriate time to declassify the Board. This determination by the Board furthers its goal of ensuring that the Company's corporate governance policies maximize management accountability to shareholders and will expireallow shareholders the opportunity each year to register their views on the performance of the Board.

        In connection with the amendment to our Bylaws to declassify our Board and in order to implement the provisions thereof, each of our directors whose terms would not have otherwise expired at the 2004 Annual Meeting of Shareholders. The term of the Class II directors, B. Thomas Golisano, John F. Kenny, Jr. and Vincent J. Ryan,has executed a resignation whereby he will expireresign at the 20052004 Annual MeetingMeeting. As a result, the terms for all of Shareholders. Directors of each class hold office untilour directors will end at the third annual meeting of the shareholders of the Company following their election or until their successors are elected and qualified.

2004 Annual Meeting. At the Annual Meeting, three Class IIIall directors are to be elected for one-year terms to serve until the Company's 20062005 Annual Meeting of Shareholders, or until their successors are elected and qualified. J. Peter Pierce resignedEugene B. Doggett's term as a Class III director on December 23, 2002,will also terminate as of the 2004 Annual Meeting and he has elected not to seek re-nomination as a result of his resignation, he has not been nominated to serve again.director. The Board has elected to reduce the size of the Board to nineeight directors, and therefore is only nominating three Class III directors. Proxies may not be votedeight directors for a greater number of individuals than the three nominees named.election. The Board has selected as nominees the following current Class III directors of the Company: Clarke H. Bailey, Constantin R. Boden, Kent P. Dauten, B. Thomas Golisano, John F. Kenny, Jr., Arthur D. Little, and C. Richard Reese.Reese and Vincent J. Ryan. Each has agreed to serve if elected, and management has no reason to believe that any of the nominees will be unavailable to serve.

        The Company's executive officers were last elected on May 23, 2002.22, 2003. At a meeting to be held immediately following the Annual Meeting, the Board currently intends to elect executive officers of the Company. All executive officers hold office at the discretion of the Board until the first meeting of

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the Board following the next annual meeting of shareholders or until their successorsthey sooner die, resign or are chosen and qualified.removed. Except for T. Anthony Ryan, the Company's Vice President, Real Estate, and Vincent J. Ryan, a Class II director, who are brothers, there are no family relationships between or among any of the Company's officers or directors.

Required Vote

        The affirmative vote of holders of a plurality of the votes properly cast at the Annual Meeting is required to elect each Class III director. For purposes of determining which nominees receive a plurality, only those cast "For" are included, and any abstentions or broker non-votes will not count in making that determination.

        The Board recommends that you vote FOR the election of each of the nominees listed below to serve as Class III directors of Iron Mountain until the 20062005 Annual Meeting of Shareholders, or until their successors are elected and qualified.

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        Set forth below is the name and age of each Class III director nominated to serve an additional term, his principal occupation and business experience during the past five years and the names of certain other companies of which he served as a director, as of April 1, 2003.2004.

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        Set forth below is the name and age of each other director and executive officer of the Company, his principal occupation and business experience during the past five years and the names of certain other companies of which he served as a director, as of April 1, 2003.

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5

        Set forth below is the name and age of each executive officer of the Company who is not a director, his principal occupation and business experience during the past five years and the names of certain other companies of which he served as a director, as of April 1, 2004.

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Director Compensation

        Directors who are employees of the Company do not receive additional compensation for serving as directors. Each director who is not an employee of the Company receives an annual retainer fee of $12,000$20,000 as compensation for his services as a member of the Board and $500$1,000 for attendance at Board and committee meetings ($1,000 per meeting formeetings. In addition, committee chairmen of the Compensation and Nominating and Governance Committees receive an annual retainer of $5,000; the chairman of the committee). In addition,Audit Committee receives an annual retainer of $20,000; and the "lead director" receives an annual retainer of $25,000. The Company also has a program by which it grants its nonemployee directors options to purchase $200,000shares of the Company's Common Stock every three years. Prior to May 23, 2002, each option was granted under eitheryears in an amount such that the Iron Mountain Incorporated 1995 Stock Incentive Plan (the "1995 Plan") or the Iron Mountain Incorporated 1997 Stock Option Plan (the "1997 Plan"). In May, 2002, the shareholders approved the adoptionproduct of the Iron Mountain Incorporated 2002 Stock Incentive Plan (the "2002 Plan"). Sinceexercise price and the approvalnumber of shares covered by the 2002 Plan, options will be granted under the 2002 Plan and grants are no longer being made under the 1995 Plan or the 1997 Plan.grant equals $200,000. Each such option has an exercise price equal to fair market value (as defined in the relevant plan) on the date of grant, vests in equal amounts over a period of three years (subject to the optionee's continuing to be a director) and has a ten year term. Options have been and will continue to be granted under the Iron Mountain Incorporated 2002 Stock Incentive Plan (the "2002 Stock Incentive Plan"). All directors are reimbursed for out-of-pocket expenses incurred in attending meetings of the Board or committees thereof, and for other expenses incurred in their capacities as directors.

The Company paid a total of $131,000$178,000 in cash for directors fees in respect of services for 2002.2003.

Board of Directors and Committee MeetingsCommittees

        Independence.    The Board is comprised of a majority of directors who qualify as independent directors pursuant to the corporate governance standards for companies listed on the New York Stock Exchange ("NYSE"). In determining independence pursuant to NYSE standards, each year the Board affirmatively determines whether directors have a direct or indirect material relationship with the Company, including its subsidiaries, that may interfere with their ability to exercise their independence from the Company. When assessing the materiality of a director's relationship with the Company, the Board considers all relevant facts and circumstances, not merely from the director's standpoint, but from that of the persons or organizations with which the director has an affiliation. Material relationships can include commercial, industrial, banking, consulting, legal, accounting, charitable and familial relationships.

        The Board has determined that the following directors qualify as independent under NYSE rules: Messrs. Bailey, Boden, Dauten, Golisano and Little. The Board has also determined that Mr. Doggett, who is not seeking re-nomination, is an independent director under the NYSE rules. The Board has concluded that none of these directors possessed the categorical relationships set forth in the NYSE listing standards that prevent independence. None of our independent directors has any relationship with the Company other than his service as a director and on committees of the Board.

        Two of our directors, Messrs. Kenny and Reese, are management employees involved in our day to day activities and are not considered to be independent directors. Additionally, although none of the relationships Mr. Ryan has with the Company would be sufficient to classify him as not independent under NYSE rules, the Board has determined not to consider Mr. Ryan as an independent director due to his position with Schooner, the familial relationship between Mr. Ryan and T. Anthony Ryan, an officer of the Company, and Schooner's lease with the Company.

        Attendance.    During the fiscal year ended December 31, 2002,2003, the Board held four regular meetings and threefour special meetings.meetings and took one action by written consent. Each incumbent director who was then in office, other than Mr. Golisano, attended at least 75% of the aggregate number of meetings of the Board and all committees thereof on which such director served. All of our directors attended our 2003 annual meeting of shareholders. All directors are expected to attend the annual meeting of shareholders. Our policy with respect to directors' attendance at our annual meetings of shareholders can be found in our corporate governance guidelines, the full text of which appears in the "Investor Relations/Governance" section of our website at www.ironmountain.com.

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        Committees.The Board of the Company has a standing Audit Committee, Executive Committee, Nominating and Governance Committee, Compensation Committee and a Stock Incentive Plan Subcommittee of the Compensation Committee (the "Incentive Plan Subcommittee"). In addition,The Board has adopted charters for the Audit Committee, Compensation Committee and Nominating and Governance Committee, each of which is available on December 5, 2002,our website at www.ironmountain.com under the heading "Investor Relations/Governance." The Board establishedand each of the Audit Committee, Compensation Committee and Nominating and Governance Committee have conducted and will continue to conduct annual self-evaluations. These self-evaluations are intended to facilitate an examination and discussion by the entire Board and each of these committees of their effectiveness as a Nominating/Governance Committee.group in fulfilling charter requirements and other responsibilities, as well as areas for improvement. During the fiscal year ended December 31, 2002,2003, the Audit Committee held 11eight meetings, the Executive Committee held threefive meetings and took threetwo actions by written consent, the Compensation Committee held five meetings, the Nominating and Governance Committee held one meeting and the Incentive Plan Subcommittee held one meeting and took five actions by written consent.three meetings.

        Audit Committee.    The Audit Committee consists of three members, Messrs. Boden (Chairman), Little and Dauten, each of whom is independent as defined by New York Stockthe rules of the Securities and Exchange Commission ("NYSE"SEC"), NYSE listing standards and the Audit Committee Charter. The Board has determined that Mr. Boden is an audit committee financial expert as defined by the rules of the SEC. Additionally, the Board has determined that each of the three members of the Audit Committee is financially literate as defined by the NYSE listing standards. The Audit Committee operates under a written charter adopted by the Board, which is filedattached to this proxy as an exhibit to the Company's Schedule 14A filed in April 2001.Appendix A. The Audit Committee selects and evaluates(1) assists the Board in oversight of the integrity of the Company's independent auditors, including their independence, reviews the audited financial statements, (2) assists the Board in oversight of the Company's compliance with legal and approves them for inclusionregulatory requirements, (3) assists the Board in oversight of the independent auditor's qualifications and independence, (4) assists the Board in the Company's Annual Report on Form 10-K, and discusses the adequacyperformance of the Company's internal controls with managementaudit function and independent auditors, (5) prepares an Audit Committee report as required by the auditors, amongSEC to be included in the annual proxy statement, (6) performs such other duties as the Board may assign to the Committee from time to time and (7) takes other actions taken to meet its responsibilities as set forth in its written charter. The Audit Committee is also responsible for establishing procedures for the receipt, retention and treatment of complaints regarding accounting, internal accounting controls and auditing matters, including procedures for the confidential and anonymous submission by employees of the Company of any concerns regarding accounting or auditing matters they think may be questionable. Information about these procedures can be found on our website in the "Investor Relations/Governance" section under the "E-mail Alert" heading at www.ironmountain.com.

        Executive Committee.    The Executive Committee consists of Messrs. Ryan (Chairman), Reese and Bailey. Between meetings of the Board, the Executive Committee exercises all the powers of the Board in the management and direction of the business and affairs of the Company to the extent not otherwise prohibited by law, the Board, the Company's Amended and Restated Bylaws or Amended and Restated Articles of Incorporation.

        Compensation Committee.    For the year ended December 31, 2003, the Compensation Committee consisted of Messrs. Bailey (Chairman), Boden, Little and Ryan. Each of these directors is independent as defined by NYSE listing standards with the exception of Mr. Ryan, who, as discussed above under "Independence," the Company has determined not to consider independent. Mr. Ryan has resigned from the Compensation Committee effective March 5, 2004. Upon Mr. Ryan's resignation, all of the members of the Compensation Committee qualify as independent under NYSE listing standards. The Compensation Committee (1) creates shareholder value by ensuring market-driven, competitive and equitable compensation systems for senior officers that create both short- and long-term incentives, (2) takes actions to retain a skilled, creative and professional management team at the most economical cost, (3) ensures that compensation policies and programs are compliant with applicable laws and are

8

administered without bias or prejudice, (4) takes actions to maintain a compensation philosophy of "paying for performance" for senior management, (5) develops and proposes for consideration by the Board compensation policies for the Company's non-employee directors that enable the Company to retain highly qualified individuals for such positions and (6) takes other actions to meet its responsibilities as set forth in its written charter.

        Nominating and Governance Committee.    The Nominating and Governance Committee consists of Messrs. Little (Chairman), Boden Ryan and Bailey.Golisano, each of whom is independent as defined by NYSE listing standards. The CompensationNominating and Governance Committee provides recommendations(1) recommends the composition and size of the Board, (2) identifies and recommends candidates for nomination to the Board, regarding Iron Mountain's compensation policies and programs and is also responsible for establishing and modifying(3) recommends to the compensation for allBoard statements of the Company's executive officers. Ifduties and responsibilities of each committee and subcommittee of the SEIP is approved,Board, (4) develops and recommends to the Compensation Committee will also administerBoard and implements corporate governance guidelines applicable to the SEIP.Company, (5) assists the Board in reviewing management succession, (6) develops and monitors an annual process to assess the effectiveness of the Board and the Board's standing committees and (7) takes other actions to meet its responsibilities as set forth in its written charter.

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        Incentive Plan Subcommittee.    The Incentive Plan Subcommittee consists of Messrs. Little (Chairman) and Boden, both of whom are "outside" and "non-employee" directors within the meaning of Section 162(m) of the Internal Revenue Code of 1986, as amended (the "Code"), and the regulations thereunder, and Rule 16b-3 under Section 16 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), respectively. The Incentive Plan Subcommittee currently administers the 2002 Stock Incentive Plan, including the grant of stock options under the 2002 Stock Incentive Plan to all employees, including executive officers.officers and directors. The Incentive Plan Subcommittee also administers the 2003 Employee Stock Purchase Plan (the "ESPP"), the Iron Mountain Incorporated 1995 Stock Incentive Plan (the "1995 Plan"), the Iron Mountain Incorporated 1997 Stock Option Plan (the "1997 Plan"), the Iron Mountain/ATSI 1995 Stock Option Plan and the Nonqualified Stock Option Plan of Pierce Leahy Corp., and recommends the adoption of, and any amendments to, all stock incentive plans. There are no shares available for grant under the 1995 Plan and the 1997 Plan, other than shares that become available under such plans in the future as a result of the lapse or cancellation of outstanding stock options. There are no shares available for grant under the Iron Mountain/ATSI 1995 Stock Option Plan or the Nonqualified Stock Option Plan of Pierce Leahy Corp. If the ESPP is approved, the Incentive Plan Subcommittee will administer such plan. The Incentive Plan Subcommittee also administers the Iron Mountain Incorporated Executive Deferred Compensation Plan, a nonqualified deferred compensation plan (the "Executive Deferred Compensation Plan").

Meetings of Independent/Non-Management Directors

        In accordance with NYSE listing standards and pursuant to our Corporate Governance Guidelines, our non-management directors meet at regularly scheduled executive sessions and may hold such additional executive sessions as they determine necessary or appropriate. One of our non-management directors, Mr. Ryan, has been determined by the Board not to be considered independent as defined by the NYSE listing standards; the independent directors meet at least once each year without such non-independent director. The Board has named Mr. Boden as the lead director and he acts as the chair of the executive sessions.

Shareholder Communications to Board of Directors

        The Nominating/Governance Committee consists of Messrs. Little (Chairman)Board believes it is important for shareholders and Boden. The Nominating/Governance Committee, which was recently established, will, among other things, (1) identify and recommend candidates for nominationothers to have a process to send communications to the Board. Accordingly, any shareholder, security holder or other interested party who desires to communicate with the Board, (2) recommendany individual director, including the lead director, or the independent or non-management directors as a group, may do so by regular mail or e-mail directed to the Board statementsSecretary of the duties and responsibilities of each committee and subcommittee ofCompany. The Secretary's mailing address is c/o Iron Mountain, 745 Atlantic Avenue,

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Boston, Massachusetts 02111; the Board, (3) recommendSecretary's e-mail address is corporatesecretary@ironmountain.com. Upon receiving mail addressed to the Board, the numberSecretary will assess the appropriate director or directors to receive the message, and will forward the mail to such director or directors without editing or altering it.

Selection of members of each committee and subcommittee, and (4) recommendCandidates for Directors

        The Board as a whole is responsible for nominating individuals for election to the Board matters related to governanceby the shareholders and for filling vacancies on the Board that may occur between annual meetings of the Company, such as director independence, qualifications, experience requirements, minimum attendance requirements, management succession planningshareholders. The Board is also responsible for developing and the role of the "lead" director. A proposed Nominating/approving criteria, in addition to those set forth in our Corporate Governance Guidelines, for candidates for Board membership. The Nominating and Governance Committee Charter outlining these responsibilities is being considered byresponsible for seeking candidates to become Board members, consistent with the Nominating/criteria set forth in the Corporate Governance Committee.

Resignation of Director

        On December 23, 2002, J. Peter Pierce tendered his resignation as a director. By letter to Mr. Pierce dated December 20, 2002, the Company's directors had requested that Mr. Pierce resign as a director (the "Board's Letter"). Mr. Pierce stated in his resignation letter that he was not resigning as a result of the Board's Letter. Instead, Mr. Pierce stated that his resignation was prompted by his disagreement as to certain procedures followed by the Company,Guidelines and the Board, in respect of the Company's disputes with Mr. Pierce, which include pending litigation and arbitration proceedings against him related to Mr. Pierce's alleged involvement with and support of Sequedex LLC, a competitor of the Company. Mr. Pierce contended that the actions taken against him were not authorizedapproved by the Board, and for recommending candidates to the entire Board for selection by the Board for nomination to fill vacancies on the Board or expiring terms of directors at each annual meeting of shareholders.

        Nominees for director will be selected on the basis of their integrity, experience, achievements, judgment, intelligence, personal character, ability to make independent analytical inquiries, willingness to devote adequate time to Board duties, and likelihood that he or she will be able to serve on the Company did not adequately disclose its actionsBoard for a sustained period. The Nominating and Governance Committee will consider, as part of the process for identifying individuals who might be candidates, individuals who are properly recommended by shareholders for nomination by the Board at a meeting of shareholders at which directors are to be elected. To be proper, a recommendation for a nominee for director with regardrespect to Mr. Pierce. Mr. Pierce also states that his resignation froma meeting of shareholders must comply with applicable law, the Company's bylaws, the Nominating and Governance Committee Charter and the Company's Corporate Governance Guidelines. The Nominating and Governance Committee will consider any suggestions offered by other directors or shareholders with respect to potential directors and there will be no difference in the manner in which potential nominees are evaluated. However, the Nominating and Governance Committee, and the Board, will enable himnot be required to pursue shareholders' rightsenlarge the size of the Board in order to nominate an otherwise fully qualified candidate proposed by a shareholder.

        In 2003, we did not pay a fee to any third party to identify or evaluate or assist in identifying or evaluating potential nominees for our Board. We did not, as of December 19, 2003, receive any recommendations from shareholders for nominees for the Board.

Nominations and Proposals of Shareholders

        The Company expects to hold the 2005 Annual Meeting on May 26, 2005.

     ��  To be eligible for consideration at our 2005 Annual Meeting, shareholder nominations of a person (or persons) to be elected as a director (or directors) must be received at our principal executive office no earlier than December 23, 2004, and no later than January 22, 2005. Shareholder nominations must also be made in compliance with the other interested shareholdersrequirements for shareholder nominations set forth in our Bylaws and Corporate Governance Guidelines.

        A shareholder who intends to ensurepresent a proposal at the 2005 Annual Meeting of Shareholders and who wants the proposal included in the Company's 2005 proxy statement and proxy card relating to that meeting must submit the Company is governedproposal by December 23, 2004. In order for the proposal to be included in the proxy statement, the shareholder submitting the proposal must meet certain eligibility standards and managed properly. Finally, Mr. Pierce objectedcomply with certain procedures established by the SEC, and the proposal must comply with the requirements as to form and substance established by our Bylaws and applicable laws and regulations. The proposal must be mailed to the Company's involvement with Thomas Carr, a business associate of Mr. Pierce,principal executive office, at the address stated herein, and to the failure of the Company to disclose a lawsuit between Mr. Carr and Mr. Pierce.

        The Company does not agree with Mr. Pierce's position and certain of his factual statements. When the Company's management began receiving information in the autumn of 2000 that Sequedex had been established by certain former executives of Pierce Leahy Corp. (some of which had noncompetition agreements with the Company), and also that Mr. Pierce was directly involved with Sequedex, managementshould be directed the Company's outside counsel to conduct a confidential investigation of these matters under the direction of Mr. Reese and the members of the Company's Executive Committee, other than Mr. Pierce. As a result of counsel's confidential investigation and discovery in

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lawsuits against certain former employees of the Company and Sequedex, the Company's management and the Board, other than Mr. Pierce, concluded that Mr. Pierce had breached noncompetition and nonsolicitation agreements with, as well as his fiduciary obligations to, the Company, both directly and indirectly, by reason of his involvement with and support of Sequedex. In order to preserve the confidential character of the investigation, as well as to prevent the potential destruction of evidence and the premature or inaccurate disclosures of these matters, the Company's management and the Board met informally on several occasions. The Company believes that its procedures were appropriate, given the unusual circumstances in the situation. As a result of the information that came to the attention of the Company's managementChief Financial Officer.

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        A shareholder who intends to present a proposal at the 2005 Annual Meeting of Shareholders and who intends to conduct his, her or its own proxy solicitation must submit the Board,proposal to the Company on March 28, 2002, initiatednot earlier than January 22, 2005 and not later than February 21, 2005.

Code of Ethics

        We have adopted a civil action against Mr. PierceCode of Ethics and others in the Superior Court of New Jersey, Middlesex County, Chancery Division, and subsequently, on April 15, 2002, initiated an arbitration proceeding against Mr. Pierce. The Company's effortsBusiness Conduct that applies to resolve its disputes with Mr. Pierce, Sequedex and the other defendants were rejected. Mr. Pierce contends that the Company authorized the payment of $50,000 to Mr. Carr and his attorneys to fund a lawsuit against Mr. Pierce without independent knowledge as to its merits. The Company disagrees with Mr. Pierce's characterization of its dealings with Mr. Carr, who first approached the Company's management in the autumn of 2001 with information that, among other things, Mr. Pierce, who had acquired a controlling interest in Mr. Carr's transportation, warehousing and logistics company earlier that year, was utilizing that company surreptitiously to provideeach employee, support, transportation services and advertising for Sequedex. The information provided by Mr. Carr was consistent with other information that had come to management's attention as a result of the investigation and discovery described above. On April 9, 2002, after the Company was notified that Mr. Carr had commenced an independent lawsuit against Mr. Pierce, management concluded that it was in the best interestsincluding officers, of the Company and all directors. Our Code of Ethics and Business Conduct is posted on our website at www.ironmountain.com under the heading "Investor Relations/Governance." A printed copy of our Code of Ethics and Business Conduct is also available free of charge to any shareholder who requests a copy. We intend to satisfy our disclosure requirement regarding any amendment to, or waiver from, a provision of our Code of Ethics and Business Conduct applicable to the Company's chief executive officer, chief financial officer or principal accounting officer or controller by posting such information on our website or in a report on Form 8-K. Any waivers applicable to any other executive officers will also be promptly disclosed to shareholders on our website.

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ITEM 2

AMENDMENT TO THE COMPANY'S AMENDED AND RESTATED
ARTICLES OF INCORPORATION TO INCREASE THE AUTHORIZED SHARES
OF COMMON STOCK

Proposed Amendment

        The Pennsylvania General Corporation Law provides that the total number of shares of each class of stock that a corporation is authorized to issue shall be set forth in its Articles of Incorporation. The Company's Amended and Restated Articles of Incorporation (the "Restated Articles") presently authorize the Company to issue 150,000,000 shares of Common Stock and 10,000,000 shares of Preferred Stock.

        As of April 1, 2004, 85,841,854 of the authorized shares of Common Stock and no shares of Preferred Stock were issued and outstanding. The Board has unanimously approved, and unanimously recommends that the shareholders of the Company approve, a proposal to amend the first sentence of Article FOURTH of the Restated Articles to increase the number of shares of Common Stock that the Company is authorized to issue from 150,000,000 to 200,000,000 shares. The full text of the first sentence of Article FOURTH of the Articles of Incorporation as proposed to be amended by this proposal is as follows: "FOURTH: The aggregate number of shares which the corporation shall have authority to issue is Two Hundred Ten Million (210,000,000) shares, to be divided into Two Hundred Million (200,000,000) shares of Common Stock, par value $0.01 per share and Ten Million (10,000,000) shares of Preferred Stock, par value $0.01 per share."

Reasons for and General Effect of the Proposed Amendment

        The Board of Directors believes that the current level of authorized shares of Common Stock may restrict the Company's ability to issue or reserve Common Stock for general corporate purposes. The purpose of the proposed amendment is to provide $50,000sufficient authorized shares of Common Stock to give the Board the flexibility to issue Common Stock in financial support to Mr. Carr's counselthe future in order to ensureconnection with stock dividends, acquisitions and other transactions that management believes would provide the facts relating to certainpotential for growth and for other general corporate purposes. If the proposed amendment is adopted, there will be 114,158,146 shares of Mr. Pierce's actions in derogationCommon Stock authorized and unissued, based on the number of his contractualshares outstanding and fiduciary obligationsreserved as of April 1, 2004.

        No further action or authorization by the Company's shareholders would be necessary prior to the issuance of additional shares of Common Stock, except as may be required for a particular transaction by applicable law or regulatory agencies or by the rules of the NYSE or any other stock exchange on which the Company's securities may then be listed. If additional shares are available, transactions dependent upon the issuance of additional shares would be less likely to be impeded or undermined by delays and uncertainties occasioned by the need to obtain prior shareholder authorization. The ability to issue shares, as deemed in the Company's best interests by the Board, may also permit the Company were fully developed.to avoid expenses incurred in holding special shareholders' meetings in the future.

9        At the present time, the Board has no specific plans to issue or reserve additional shares of Common Stock other than in connection with routine grants under the 2002 Stock Incentive Plan or any similar replacement plan and issuances of shares under the ESPP. Shareholders of the Company have no preemptive rights with respect to any shares of the Company's Common Stock.

Certain Effects of the Proposed Amendment

        The issuance of additional shares of Common Stock by the Company could have an antitakeover effect by making it more difficult to obtain shareholder approval of various actions, such as a merger or removal of management. Additionally, the issuance of additional shares of Common Stock by the Company could have the effect of diluting existing shareholder earnings per share, book value per share and voting power. The amendment to the Restated Articles, if approved, could strengthen the

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position of management and might make the removal of management more difficult, even if removal would be generally beneficial to the Company's shareholders. The authorization to issue the additional shares of Common Stock would provide management with a capacity to counter the efforts of unfriendly tender offerors by issuing securities to others who are friendly or desirable to management. However, the submission of the proposed amendment to the Restated Articles is not a part of any present plan by the Company's management to adopt a series of amendments to the Company's Articles of Incorporation or Bylaws so as to render the takeover of the Company more difficult.

        The proposed amendment to the Restated Articles is not the result of management's knowledge of any specific effort to accumulate the Company's securities or to obtain control of the Company by means of a merger, tender offer, proxy solicitation in opposition to management or otherwise.

Required Vote

        The affirmative vote of the holders of a majority of the votes properly cast at the Annual Meeting is required to approve the amendment to the Company's Restated Articles. For purposes of determining whether a majority of the votes have been cast in favor of the approval of the amendment to the Company's Restated Articles, only those cast "For" or "Against" are included, and any abstentions or broker non-votes will not count in making that determination.

The Board recommends that you vote FOR the proposal to amend the Company's Restated Articles to increase the number of authorized shares of Common Stock from 150,000,000 to 200,000,000.

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ITEM 23

APPROVAL OF

AMENDMENT TO THE IRON MOUNTAIN INCORPORATED
2003 EMPLOYEE2002 STOCK PURCHASEINCENTIVE PLAN

        The Company's Board has unanimously approved, and is proposing for shareholder approval,unanimously recommends that the ESPP. The purpose of the ESPP is to provide employeesshareholders of the Company and its subsidiariesapprove, an amendment to the opportunity2002 Stock Incentive Plan, attached as Appendix B, to acquire an equity interest inincrease the Company by providing favorable termsnumber of shares of Common Stock authorized for themissuance under the 2002 Stock Incentive Plan from 1,352,543 to purchase the Company's Common Stock.3,352,543.

        The Board believes that equity-based compensation isequity interests are a significant factor in the Company's ability to attract, retain and motivate itskey employees, whodirectors and other service providers that are critical to the Company's long-term success and that an increase in the adoptionnumber of shares available for issuance under the ESPP will further the goal of providing employees2002 Stock Incentive Plan is necessary in order to provide those persons with incentives to serve the Company.

        On In approving the increase in the number of shares reserved for issuance under the 2002 Stock Incentive Plan, the Board considered that only approximately 550,000 shares were available for grant under the 2002 Stock Incentive Plan as of April 1, 2004, the average annual rate of grants during 2001 through 2003, and the closing price per shareportion of the Company's Commonoutstanding shares represented by shares subject to options, relative to other publicly held companies in related businesses.

Summary of the 2002 Stock as listed on the NYSE, was $38.54.

2003 Employee Stock PurchaseIncentive Plan

        The following summary of the material features of the 2003 Employee2002 Stock PurchaseIncentive Plan is qualified in its entirety by reference to the complete text of the ESPP, attached2002 Stock Incentive Plan, which is filed as Appendix Aan appendix to thisthe Company's Proxy Statement.Statement on Schedule 14A filed in April 2002.

        Overview.        The ESPP operates by granting, in a series2002 Stock Incentive Plan permits the issuance of offerings,equity-based awards, including incentive stock options, nonqualified stock options, grants of Common Stock, whether or not subject to acquire the Company'srestrictions, and stock appreciation rights. The 2002 Stock Incentive Plan initially reserved 1,352,543 shares of Common Stock. TheIf shareholders approve the amendment to the 2002 Stock Incentive Plan, Subcommittee determines the commencement date and duration of offerings. The Incentive Plan Subcommittee may also limit the maximumtotal amount of Common Stock available with respect to an offering.

        Provided the ESPP is approved by shareholders, the first offering is anticipated to commence on or about July 1, 2003. In general, offerings will last for six months and will begin each June 1 and December 1. During an offering, payroll deductionsreserved will be accumulated on behalf of each participant. At the end of the offering, the options will be exercised and the accumulated payroll deductions will be retained by the Company as full payment of the option price. Each participant will receive a number of shares of the Company's Common Stock equal to the accumulated payroll deductions credited to the participant's account as of the exercise date divided by the option price. The "option price" of shares of Common Stock will be 85 percent of the lower of the fair market value of the Company's shares at the start of the offering or on the exercise date. Fair market value under the ESPP means the average of the highest and lowest sale price of the Company's Common Stock on the date in question. The Incentive Plan Subcommittee may, with respect to a future offering, reduce (or eliminate) the option price discount or apply any discount only to the fair market value of the shares on the exercise date.3,352,543.

        Shares Available under the ESPP.Purpose, Eligible Individuals, Effective Date and Duration.    The total number of shares that may be subject to options under the ESPP is 750,000. This is projected to provide enough shares to keep the ESPP in place for at least three years (based on past experience with the 1998 Employee2002 Stock Purchase Plan). In order to ensure that sufficient shares remain available for at least three years, the Incentive Plan Subcommittee may impose a cap onwas effective April 1, 2002. The purpose of the amount of Common2002 Stock available with respectIncentive Plan is to any offering.

        If an option expires or is terminated or surrendered, the shares allocable to the option may again be available under the ESPP. If insufficient shares are available at the end of an offering, a pro rata allocation of remaining shares will be made.

        Eligibilityencourage employees, officers, directors and Participation.    In general, any employeeconsultants of the Company and our subsidiaries who render services to our management, development or a subsidiary that is (or is treatedoperation to continue their association with us by providing favorable opportunities for federal income tax purposes as) a corporation who is customarily employed for more than five months in a calendar year may become a participant in any future offering under the ESPP by electing to participate prior to the commencement of the offering. However, the following persons are

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ineligiblethem to participate in the ESPP: (1) any employee who owns,ownership of our Common Stock and in our future growth through grants of our Common Stock, with or without restrictions, options to acquire our Common Stock and other rights to compensation in amounts determined by the value of our Common Stock (collectively, "Awards"). For this purpose, subsidiaries include corporations, companies, partnerships and other forms of business organizations in which we own directly or indirectly as of the start of an offering, five percent or more of the Company's stock or the stock of one of the Company's corporate subsidiaries; (2) any employee of a subsidiary that does not elect to participate in the ESPP; (3) any union employee, if the union elects not to participate in the ESPP; (4) any individual who is not an employee, including outside directors, consultants and independent contractors; and (5) any employee hired fewer than six months prior to the commencement of an offering. In addition, an employee will not be granted an option that would permit him or her to own (or be considered to own) or hold outstanding options to purchase five percent50% or more of the total combined voting power or value of all classes of the Company's stock or thatother form of equity ownership or in which we have a corporate subsidiary, and a participant cannot acquire in any year more than $25,000 worthsignificant financial interest. The recipient of an Award is referred to as an "Optionee." At this time, approximately 13,000 persons are eligible to receive options pursuant to the 2002 Stock Incentive Plan.

        The 2002 Stock Incentive Plan will terminate on March 31, 2012, unless earlier terminated by the Board. Termination of the Company's stock under the ESPP (based on the value of the Company's stock at the start of the offering).

        A participant may authorize payroll deductions of from one to 15 percent of the participant's cash compensation on each pay date. A participant can decrease his or her rate of payroll deductions, but the participant can never increase the rate of payroll deductions once an offering begins.

        A participant may,2002 Stock Incentive Plan will not affect Awards made prior to the end of an offering period, and at such time and in such manner as the Incentive Plan Subcommittee may prescribe, withdraw from an offering and request payment of an amount in cash equal to the accumulated payroll deductions credited to the participant's account under the ESPP. Intermination, but no eventAwards will a participant receive interest with respect to his or her payroll deductions, whether used to exercise options or returned in cash.be made after termination.

        Termination of Employment.Shares Subject to the 2002 Stock Incentive Plan.    Upon terminationThe total number of employmentshares of our Common Stock that may be subject to Awards under the 2002 Stock Incentive Plan may not exceed 1,352,543 shares, or 3,352,543 shares if the amendment is approved. The shares may be authorized but unissued shares or treasury shares. The total amount of Common Stock that may be granted under the Plan to any single person in any calendar year may not exceed in the aggregate 500,000 shares. To the extent that

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an option or other form of Award lapses or is forfeited, the shares subject to the Award will again become available for any reason other than death,grant under the participant will receive a payment in cashterms of the amount credited to the participant's account under the ESPP.2002 Stock Incentive Plan.

        In the event thatof any change in the number of shares or kind of Common Stock outstanding pursuant to a participant dies priorreorganization, recapitalization, exchange of shares, stock dividend or split or combination of shares, appropriate adjustments will be made to the endnumber of an offering period,shares of authorized Common Stock, to the participant's account willnumber of shares of Common Stock subject to outstanding Awards, to the exercise price per share of options and other forms of Awards and to the kind of shares that may be paid in cash to his or her estate.

        Restrictions on Transfer.    A participant may not transfer, assign, pledge or otherwise dispose of an option issued under the ESPP. Shares acquired2002 Stock Incentive Plan.

        As of April 1, 2004, 785,064 options to purchase shares of Common Stock were outstanding under the ESPP at the end of an offering period will be freely tradable, subject in all cases to the participant's compliance with the Company's Statement of Insider Trading Policy.2002 Stock Incentive Plan.

        Administration.    IfAlthough the ESPP is approved byBoard has the shareholders,authority to administer the Plan, it will have an effective date of April 7, 2003, and will be administered byhas generally delegated this authority to the Incentive Plan Subcommittee.Subcommittee, which administers all of our equity-based compensation plans. Each member of the Incentive Plan Subcommittee is a "non-employee director" within the meaning of Rule 16b-3 promulgated under the Exchange Act and an "outside director" within the meaning of Section 162(m) of the Code.

        Subject to the terms of the 2002 Stock Incentive Plan, the Incentive Plan Subcommittee has the authority to: (1) select Optionees; (2) determine the terms and conditions of Awards, including the price to be paid by an Optionee for any Common Stock; and (3) interpret the 2002 Stock Incentive Plan and prescribe rules and regulations for its administration.

        Stock Options.    The Incentive Plan Subcommittee will havemay grant incentive stock options and nonqualified stock options under the authority2002 Stock Incentive Plan. The Incentive Plan Subcommittee determines the number of shares of Common Stock subject to adopt, amendeach option, its exercise price, its duration and rescind such rulesthe manner and regulations as, in its opinion,time of exercise. Incentive stock options may be advisable in the administration of the ESPP andissued only to decide all questions of interpretation and application of such rules and regulations, which decision will be final and binding.

        Forfeiture for Dishonesty.    If the Board determines that a participant has engaged in fraud, embezzlement, theft, commission of a felony or proven dishonesty in the course of his or her employment that has damaged the Company or a subsidiary or has disclosed trade secrets or other proprietary informationemployees of the Company or of a corporate subsidiary (1) the individual's participation in the ESPP will terminateof ours, and the participant will forfeit his or her rightexercise price must be at least equal to receive anythe fair market value of the Common Stock that has not been delivered pursuant to an offering and (2) the Company will have the right to repurchase all or any partas of the date the option is granted. Further, an incentive stock option generally must be exercised within ten years of grant. The Incentive Plan Subcommittee, in its discretion, may provide that any option is subject to vesting limitations that make it exercisable during its entire duration or during any lesser period of time.

        The exercise price of an option may be paid in cash, in shares of Common Stock acquiredowned by the participantOptionee, by delivery of a recourse promissory note secured by the Common Stock acquired upon exercise of the earlieroption (provided that such a loan would not be available to any executive officer or director of the Company) or by means of a "cashless exercise" procedure in which a broker transmits to us the exercise price in cash, either as a margin loan or against the Optionee's notice of exercise and confirmation by us that we will issue and deliver to the broker stock certificates for that number of shares of Common Stock having an aggregate fair market value equal to the exercise price, or agrees to pay the exercise price to us in cash upon its receipt of stock certificates.

        In its discretion, and subject to the terms of the 2002 Stock Incentive Plan, the Incentive Plan Subcommittee may grant a reload option to purchase the number of shares of Common Stock delivered to us in full or partial payment of the exercise price on the exercise of any option pursuantor in full or partial payment of the tax withholding obligations resulting from the exercise of any option.

        Options are, at the discretion of the Incentive Plan Subcommittee, transferable to members of the ESPP, atOptionee's immediate family or to a pricefamily partnership or trust for the benefit of the Optionee's immediate family.

        Stock Appreciation Rights.    The Incentive Plan Subcommittee may also grant stock appreciation rights to Optionees on such terms and conditions as it may determine. Stock appreciation rights may be granted separately or in connection with an option. Upon the exercise of a stock appreciation right, the

15

Optionee is entitled to receive payment equal to the excess of the fair market value, on the date of exercise, of the number of shares of Common Stock for which the stock appreciation right is exercised, over the exercise price for the Common Stock under a related option, or if there is not a related option, over an amount paidper share stated in the agreement setting forth the terms and conditions of the stock appreciation right. Payment may be made in cash or other property, including Common Stock, in accordance with the provisions of the applicable agreement. Upon the exercise of a stock appreciation right related to an option, the option will terminate as to the number of shares of Common Stock for which the stock appreciation right is exercised.

        Stock Grants.    The Incentive Plan Subcommittee may issue shares of Common Stock to Optionees, either with or without restrictions, as determined by it in its discretion. Restrictions may include conditions that require the Optionee to forfeit the shares in the event that the holder ceases to provide services to us or one of our subsidiaries before a stated time. Unlike holders of options and stock appreciation rights, the recipient of a stock grant, including a stock grant subject to restrictions, unless otherwise provided for in a restricted stock agreement, has the rights of a shareholder of ours to vote and to receive payment of dividends on the Common Stock.

        Special Bonus Award.    The Incentive Plan Subcommittee may grant in connection with any nonqualified stock option or stock grant a special cash bonus in an amount not to exceed the lesser of (1) the combined federal, state and local income and employment tax liability incurred by the Optionee as a consequence of acquiring Common Stock on the exercise of the option or the grant or vesting of Common Stock, and the related special bonus, or (2) 30% of the imputed income realized by the Optionee on account of the exercise or vesting, and the related special bonus. A grant may also provide that the Company upon exercise, together with interest.will lend an Optionee an amount not more than the amount described in the preceding sentence, less the amount of any special cash bonus.

        Effect of Certain Corporate Changes.Transactions.    If before an offering closes,while unexercised Awards remain outstanding under the Company merges2002 Stock Incentive Plan we merge or consolidatesconsolidate with one or more corporations (whether or not the Company iswe are the surviving corporation), if we are liquidated or the Company is liquidated, sellssell or otherwise disposesdispose of substantially all of itsour assets to another entity or if there is a "change of control,"in control" then, except as otherwise specifically provided to the contrary in any applicable agreement, the Incentive Plan Subcommittee may in its discretion mayamend the terms of all unexercised Awards so that either: (1) convert outstanding options such that after the effective date of the event, each participantOptionee is entitled, upon exercise of an Award, to receive in lieu of the Company's Common Stock the number and class of

11

shares of thesuch stock or other securities to which the participanthe or she would have been entitled had the participanthe or she been a shareholder at the time of the event;event, or is entitled to receive from the successor entity a new Award of comparable value; (2) endeach Optionee is given an opportunity to exercise all or some of his or her unexercised Awards during a twenty day period ending with the offering and exerciseevent, at which time the optionsunexercised Awards will be cancelled; or (3) all unexercised Awards are cancelled as of the day before the effective date of the event.event in consideration for cash or other consideration with a value equal to the value of the shares the Optionee would have received had the Award been exercised (to the extent exercisable). In addition to the foregoing, the Incentive Plan Subcommittee may in its discretion also amend the terms of an Award by cancelling some or all of the restrictions on its exercise to permit its exercise to a greater extent than that permitted under its existing terms.

        A "changeFor these purposes, a change of control" shallcontrol will be deemed to have occurred if any person (as suchthat term is used in Section 13(d) and 14(d)(2) of the Exchange Act) other than a trust related to anany employee benefit plan maintained by the Company becomes the beneficial owner (within the meaning of Rule 13d-3 under the Exchange Act) of 50 percent50% or more of the Company'sour outstanding Common Stock, and within the period of 24 consecutive months immediately thereafter, individuals other than (1) individuals who at the beginning of such period constitute the entire Board or (2) individuals whose election, or nomination for election by the Company's shareholders, was approved by a vote of at least two-thirds of the directors then still in office who were directors at the beginning of the period, become a majority of the Board.

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        Amendment or Termination.Amendments to the 2002 Stock Incentive Plan.    The Board may modify, revise or terminate the 2002 Stock Incentive Plan at any time without a vote by shareholders, terminate or,and from time to time, amend, modify or suspendexcept that approval of our shareholders is required with respect to any amendment to change the ESPP; provided, however, that without shareholder approval there will be no: (1) change in theaggregate number of shares of Common Stock that may be issued under the ESPP; (2)2002 Stock Incentive Plan or to any person in a year, change in the class of persons eligible to participate in the ESPP;receive Awards or (3)make any other change to the ESPPchanges that requiresrequire shareholder approval under applicable law. Unless terminated earlier,Amendments adversely affecting outstanding Awards may not be made without the ESPP will terminate onconsent of the date asholder of which there are no longer any shares of Common Stock available to be offered.the Award.

        The Board may also amend the 2002 Stock Incentive Plan as necessary to enable awards to qualify for favorable foreign tax treatment in the case of an Optionee who is subject to a tax regime outside the United States.

Tax Treatment.The following description of the federal income tax consequences of the ESPPAwards is general and does not purport to be complete. In addition, the description does not discuss the tax consequences arising as a result of the participant's death or of the tax consequences of the ESPP under the laws of any state or foreign country in which the participant may reside.

        Federal Income Tax ConsequencesTreatment of Options.    An Optionee realizes no taxable income when a nonqualified stock option is granted. Instead, the difference between the fair market value of the ESPP.Common Stock acquired pursuant to an exercise of an option and the exercise price paid is taxed as ordinary compensation income when the option is exercised. The ESPPdifference is intended to constitute an "employee stock purchase plan" under Section 423measured and taxed as of the Code. As presently in effect, under Section 423date of exercise, if the Common Stock is not subject to a "substantial risk or forfeiture," or as of the Code,date or dates on which the risk terminates in other cases. An Optionee may elect to be taxed on the difference between the exercise price and the fair market value of the Common Stock on the date of exercise, even though some or all of the Common Stock acquired is subject to a participant will not realize incomesubstantial risk of forfeiture. Gain on the subsequent sale of the Common Stock acquired by exercise of the option is taxed as a result of eithercapital gain. We receive no tax deduction on the grant of a nonqualified stock option, but we are entitled to a tax deduction when the Optionee recognizes ordinary compensation income on or after exercise of the option, in the same amount as the income recognized by the Optionee.

        Generally, an option atOptionee incurs no federal income tax liability on either the start of an offering periodgrant or the exercise of an incentive stock option, although an Optionee will generally have taxable income for alternative minimum tax purposes at the endtime of an offering period andexercise equal to the Company will not be entitled to an income tax deduction at such grant date or exercise date. If the participant holds the stock acquired under the ESPP until the earlier of two years after the start of an offering or one year after the end of an offering, then upon the subsequent sale of the stock, the participant will have ordinary compensation income of the lesser of 15 percentexcess of the fair market value of the stock as ofCommon Stock subject to the start of the offering or the excess, if any, of the selling price of the stockoption over the optionexercise price. Any additional gain or loss will be treated as long-term capital gain or loss. The CompanyProvided that the Common Stock is not entitled to an income tax deduction with respect to the ordinary compensation income described above.

        If the participant disposes of the stock acquired under the ESPP before the earlier of two years after the start of the offering orheld for at least one year after the enddate of exercise of the offering, thenoption and at least two years after its date of grant, any gain realized on a subsequent sale of the Common Stock will be taxed as long-term capital gain. If the Common Stock is disposed of within a shorter period of time, the Optionee will recognize ordinary compensation income in an amount equal to the difference between the sales price and the exercise price or (if less) the difference between the fair market value at the time of exercise and the exercise price. We receive no tax deduction on the grant or exercise of an incentive stock option, but we are entitled to a tax deduction if the Optionee recognizes ordinary compensation income on account of a premature disposition of shares acquired on exercise of an incentive stock option, in the same amount and at the same time as the Optionee recognizes income.

        Tax Treatment of Stock Appreciation Rights.    An Optionee recognizes no income upon the grant of a stock appreciation right, but upon its exercise realizes ordinary compensation income in an amount equal to the cash or cash equivalent that he receives at that time. If the Optionee receives Common Stock upon exercise of the stock appreciation right, he recognizes ordinary compensation income measured by the fair market value of the Common Stock so received (or, if the Common Stock is subject to a substantial risk of forfeiture, at the date or dates on which the risk expires, unless he or she elects to be taxed currently). We are entitled to a tax deduction in the amount of ordinary compensation income recognized.

        Tax Treatment of Stock Grants.    A person who receives a stock grant without any restrictions will recognize ordinary compensation income on the fair market value of the Common Stock over the

17

amount (if any) paid for the Common Stock. If the Common Stock is subject to restrictions, the recipient generally will not recognize ordinary compensation income at the time the award is received, but will recognize ordinary compensation income when restrictions constituting a substantial risk of forfeiture lapse. The amount of such income will be equal to the excess if any,of the aggregate fair market value, as of the date the restrictions lapse, over the amount (if any) paid for the Common Stock. Alternatively, the Optionee may elect to be taxed, pursuant to Section 83(b) of the Code, on the excess of the fair market value of the stockCommon Stock at the endtime of the offeringgrant over the option price will beamount (if any) paid for the Common Stock, notwithstanding any restrictions. All such taxable amounts are deductible by us at the time and in the amount of the ordinary compensation income recognized by the Optionee.

        Section 162(m) of the Code.    Section 162(m) of the Code generally disallows an income tax deduction to public companies for compensation in excess of $1,000,000 paid in any year to the participant,chief executive officer and any of the four most highly compensated other executive officers, to the extent that this compensation is not "performance based" within the meaning of Section 162(m) of the Code. In the case of a stock plan, the performance-based exception is satisfied if, in addition to other requirements, the plan, including the amount of stock available for grant under the plan, is approved by shareholders, the grants are made by a committee of outside directors, and the Companyamount of compensation a person can receive is based solely on an increase in the value of the Common Stock after grant. If the amendment to increase the number of shares available for grant under the 2002 Stock Incentive Plan is approved by shareholders, one of the requirements for the performance-based exception will be entitled to a deductionsatisfied with respect to that income. Any additional gain or loss will be treated as short-term or long-term capital gain or loss, depending onshares awarded under the holding period.Plan.

Required Vote

        The affirmative vote of holders of a majority of the votes properly cast at the Annual Meeting is required to approve the adoptionamendment to the 2002 Stock Incentive Plan to increase the number of the ESPP.shares of Common Stock issuable thereunder from 1,352,543 to 3,352,543. For purposes of determining whether a majority of the votes have been cast in favor of the approval of the ESPP,amendment to the 2002 Stock Incentive Plan, only those cast "For" or "Against" are included, and any abstentions or broker non-votes will not count in making that determination. Additionally, NYSE rules require that at least a majority of the votes that all shareholders are entitled to cast at the Annual Meeting must vote on the Plan Amendment, whether for or against.

        The Board recommends that you vote FOR the approval of the 2003 Employeeamendment to the 2002 Stock PurchaseIncentive Plan.

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ITEM 3

APPROVALSECURITY OWNERSHIP OF THE IRON MOUNTAIN INCORPORATED
2003 SENIOR EXECUTIVE INCENTIVE PROGRAMCERTAIN BENEFICIAL OWNERS AND MANAGEMENT

        The Board has approved, and is proposing for shareholder approval, the SEIP. The purpose of the SEIP is to align the interests of shareholders with the interests of the SEIP's only participant, the Company's Chief Executive Officer. In addition, the SEIP would allow the annual performance-based compensation paid to the Chief Executive Officer to be tax deductible by the Company.

In General

        Section 162(m) of the Code generally disallows an income tax deduction to public companies for compensation in excess of $1,000,000 paid in any year to the Chief Executive Officer or any of the four other most highly compensated executive officers, to the extent that this compensation is not "performance-based" within the meaning of Section 162(m). Compensation in excess of the $1,000,000 limit may be deducted if, among other matters, amounts are paid pursuant to pre-established, objective performance goals determined by a committee consisting solely of two or more "outside directors" (within the meaning of Section 162(m)), the material terms of those goals are disclosed to and approved by shareholders and any payment is made only after a committee of outside directors certifies that the pre-established performance goals have been satisfied.

Description of the SEIP

        The SEIP was adopted after an analysis by the Compensation Committee of the total compensation package of the Chief Executive Officer relative to the total compensation of a peer group of chief executive officers. The Compensation Committee felt strongly that a significant portion of the Chief Executive Officer's compensation should be in the form of a performance-based bonus, although a decision was made by the Compensation Committee to increase the Chief Executive Officer's base salary from $700,000 to $800,000, effective April 1, 2003.

        Under the SEIP, the Chief Executive Officer is eligible for a cash bonus of up to the lesser of 2.5 times the Chief Executive Officer's base salary for the fiscal year or $2,500,000. For each fiscal year, the Compensation Committee will establish in writing the performance goals for the Chief Executive Officer. (The Compensation Committee currently satisfies the Section 162(m) requirement of consisting solely of two or more "outside directors." In the event the Compensation Committee no longer satisfies this requirement, a committee or subcommittee of the Board satisfying this requirement will assume the responsibilities of the Compensation Committee under the SEIP.) The performance goals will be established at a time when achievement of the goals is substantially uncertain (but never more than 90 days following the start of the fiscal year to which the payment relates). Because the Board and the Compensation Committee believe that the specific performance goals will constitute confidential business information, disclosure of which could adversely affect the Company, publication of the performance goals is not contemplated. The performance goals for the 2003 fiscal year have, however, been established by the Compensation Committee.

        Performance goals under the SEIP are based on achievement of established objectives relating to one or more of the following business criteria: EBITDA; gross revenue; growth rate; capital spending; return on investment capital; free cash flow; attaining budget; operating income; and achievement of stated corporate goals including but not limited to acquisitions, alliances, joint ventures and internal expansion. The objectives may, for example, be based on a percentage change or achievement of a stated objective. Further, the objectives may be adjusted as necessary to reflect acquisitions. One hundred percent of the annual SEIP limit may only be paid if all established objectives are fully achieved. If the objectives are not fully achieved, some lesser percentage of the annual limit, as determined in advance by the Compensation Committee, may be paid.

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        Under the SEIP, the Compensation Committee has the right to reduce or eliminate, in its discretion, any amount payable if certain additional criteria are not satisfied. These criteria consist of the extent to which the objectives achieved satisfy the Company's short-term or long-term goals, the confidence of shareholders in the Company, as evidenced in part by the Company's stock price, the effectiveness of the Company and the wellness of the Company as a whole, taking into account, for example, labor relations and other similar matters.

        After the close of the Company's fiscal year, and generally before the close of the next fiscal year's first quarter, the Compensation Committee will determine the extent to which the performance goals were satisfied and will exercise its discretion in determining the final amount payable under the SEIP. No payment will be made under the SEIP without consultation with the Chairmen of the Audit and Executive Committees.

        The SEIP is intended to provide a framework within which to manage and reward the Chief Executive Officer's annual and long-term performance, clearly establish and communicate the goals and objectives for the Company, motivate and reward performance supporting the Company's business goals, link rewards with individual performance, and provide a positive compensation opportunity along with a substantial downside risk. The Board believes that the establishment of the SEIP achieves these goals.

        If the shareholders approve the SEIP, the first payment under the SEIP will be made with respect to the fiscal year of the Company that commenced on January 1, 2003.

Required Vote

        The affirmative vote of holders of a majority of the votes properly cast at the Annual Meeting is required to approve the adoption of the SEIP. For purposes of determining whether a majority of the votes have been cast in favor of the approval of the SEIP, only those cast "For" or "Against" are included, and any abstentions or broker non-votes will not count in making that determination.

The Board recommends that you vote FOR the approval of the 2003 Senior Executive Incentive Program.

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Security Ownership of Certain Beneficial Owners and Management

        The following table sets forth certain information known to the Company with respect to beneficial ownership of Common Stock by (1) each director, (2) the Chief Executive Officer and the other four most highly compensated executive officers of the Company (the "Named Executive Officers"), (3) all directors and executive officersNamed Executive Officers of the Company as a group and (4) each shareholder known by us to be the beneficial owner of more than five percent of the Common Stock. Such information is presented as of AprilMarch 1, 2003,2004, except as otherwise indicated.noted.

*

Less than 1%

(1)

Except as otherwise indicated, the persons named in the table above have sole voting and investment power with respect to all shares of Common Stock shown as beneficially owned by them.

(2)

Mr. Reese is a director, Chairman of the Board, Chief Executive Officer and President of the Company. Includes 40,43641,536 shares of Common Stock held in trusts for the benefit of Mr. Reese's children, as to which Mr. Reese disclaims beneficial ownership. Also includes 1,311,373 shares of Common Stock as to which Mr. Reese shares beneficial ownership with Schooner Capital Trust ("Schooner Trust") as a result of a 19881995 deferred compensation arrangement, as amended, between Schooner Trust and Mr. Reese relating to Mr. Reese's former services as President of the predecessor corporation to Schooner.Schooner Trust. Pursuant to such arrangement, upon the earlier to occur of (i) Schooner's(1) Schooner Trust's sale or exchange of substantially all of the shares of Common Stock held by Schooner Trust or (ii)(2) the cessation of Mr. Reese's employment with the Company, Schooner Trust is required to transfer such shares of Common Stock to Mr. Reese or remit to Mr. Reese cash in an amount equal to the then current fair market value of such shares of

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Common Stock. Schooner Trust has agreed to vote the shares of Common Stock subject to such arrangement at the direction of Mr. Reese.

15

---

(3)

Mr. Kenny is an Executive Vice President, Chief Financial Officer and a director of the Company. Includes 357,136380,166 shares that Mr. Kenny has the right to acquire pursuant to currently exercisable options.options, and 1,302 shares of which will be exercisable within 60 days.

(4)

Mr. Ebbighausen is an Executive Vice President of the Company and the President of IMOSDP, a division of IMIM. Includes 18,88829,594 shares that Mr. Ebbighausen has the right to acquire pursuant to currently exercisable options.options, and 3,221 shares of which will be exercisable within 60 days.

(5)

Mr. Miller is an Executive Vice President of the Company and the President and Chief Operating Officer of IMRM, a division of IMIM. Includes 86,74594,585 shares that Mr. Miller has the right to acquire pursuant to currently exercisable options.options, and 9,709 shares of which will be exercisable within 60 days.

(6)

Mr. Delle Donne is an Executive Vice President of the Company and the President of Enterprise Solutions and Services, a division of IMIM. Includes 40,512 shares that Mr. Delle Donne has the right to acquire pursuant to currently exercisable options.options, and 13,531 shares of which will be exercisable within 60 days.

(7)

Mr. Bailey is a director of the Company. Includes 13,91116,343 shares that Mr. Bailey has the right to acquire pursuant to currently exercisable options.

(8)

Mr. Boden is a director of the Company. Includes 13,91116,343 shares that Mr. Boden has the right to acquire pursuant to currently exercisable options.

(9)

Mr. Dauten is a director of the Company. Includes 13,91116,343 shares that Mr. Dauten has the right to acquire pursuant to currently exercisable options.

(10)

Mr. Doggett is a director of the Company. Includes 13,91116,343 shares that Mr. Doggett has the right to acquire pursuant to currently exercisable options.

(11)

Mr. Golisano is a director of the Company. Includes 22,05324,485 shares that Mr. Golisano has the right to acquire pursuant to currently exercisable options.

(12)

Mr. Little is a director of the Company. Includes 45,000 shares held by The Little Family Trust, as to which Mr. Little disclaims beneficial ownership, as well as 13,911and 10,818 shares that Mr. Little has the right to acquire pursuant to currently exercisable options.

(13)

Mr. Ryan is a director of the Company. Includes 13,91116,343 shares that Mr. Ryan has the right to acquire pursuant to currently exercisable options. Also includes: (i) 

1.

3,129,073 shares held by the Vincent J. Ryan Revocable Trust, dated December 24, 1987 ("Ryan 1987 Trust"). Mr. Ryan, as one of the two trustees of the Ryan 1987 Trust, has sole voting and dispositive power with respect to the 3,129,073 shares.

2.

300,000 shares held by the Carla E. Meyer Three-Year Retained Annuity Trust, dated August 4, 2003 ("Meyer Trust"). Mr. Ryan and Stephen Maiocco are the Trustees of the Meyer Trust. The Trustees of the Meyer Trust have joint voting and dispositive power over such shares.

3.

4,104,114 shares held by Schooner Trust. Mr. Ryan is Chairman and the beneficial owner of Schooner. On December 12, 2003, Schooner assigned to Schooner Trust a certain deferred compensation arrangement, as amended, between Schooner and C. Richard Reese relating to former services by Mr. Reese as President of Schooner. On that same date, Schooner transferred to Schooner Trust a total of 4,104,114 shares. These 4,104,114 shares include 1,311,373 shares as to which Mr. Reese shares beneficial ownership with Schooner Trust as a

20

result of such deferred compensation arrangement described above in note (2). Pursuant to such deferred compensation arrangement, upon the earlier to occur of (i) Schooner Trust's sale or exchange of all or a portion of those 1,311,373 shares, after all other shares of Iron Mountain Common Stock held by Schooner which include 1,311,373Trust have been sold, or (ii) the cessation of Mr. Reese's employment with Iron Mountain, Schooner Trust is required to transfer such shares attributable(or portion thereof) to aMr. Reese, or remit to Mr. Reese cash in an amount equal to the then current fair market value of such shares. Schooner Trust has agreed to vote the shares subject to such deferred compensation arrangement described in note (2) above as to whichat the direction of Mr. Ryan shares voting power but has sole investment power and 2,792,741 shares as to whichReese. Thus Mr. Ryan has sole voting power with respect to 2,792,741 shares held by Schooner Trust, and investmenthas sole dispositive power aswith respect to the Chairman of the Boardentire 4,104,114 shares held by Schooner Trust. Mr. Ryan is President of Schooner Trust and he, and members of his family, are the principal stockholdersole shareholders of Schooner Capital Trust,Trust.

4.

102,000 shares registered in the sole membername of Schooner; (ii) 9,000 shares held inThe Schooner Foundation, a trust for the benefitprivate non-profit foundation, of Mr. Ryan's heirs, as to which Mr. Ryan disclaims beneficial ownership except tois a trustee.



5.

9,000 shares registered in the extentname of his pecuniary interest therein; (iii) 102,000 shares held by The Schooner Foundation as toCitibank, South Dakota, Trustee of the Ryan 1988 Issue Trust, of which Mr. Ryan disclaims beneficial ownership. is the Settlor.

Mr. Ryan's address is c/o Schooner Capital LLC, 745 Atlantic Avenue, Boston, Massachusetts 02111.

(14)

Includes 608,800689,638 shares that directors and executive officers have the right to acquire pursuant to currently exercisable options.

(15)

ThisThe information is presented as of December 31, 2002,2003 and is based solely on a Schedule 13G/A filed with the Securities and Exchange Commission (the "Commission") on February 14, 2003. These securities are owned by various individual and institutional investors for which Chieftain Capital Management, Inc. ("Chieftain") serves as independent advisor with power to direct investments and/or sole power to vote the securities. Chieftain has shared voting power and shared dispositive power over all 12,575,919 shares, but disclaims beneficial ownership as to all these shares. The address of Chieftain is 12 East 49^th Street, New York, New York 10017.

16

(16)

This information is presented as of December 31, 2002, and is based solely on a Schedule 13G13F filed with the Commission on February 14, 2003. The17, 2004 by Berkshire Hathaway Inc. and Warren E. Buffett. Based on the information provided in such Schedule 13F, the relevant members of the filing group, together with their respective addresses are: Warren E. Buffett, 1440 Kiewit Plaza, Omaha, NE 68131; Berkshire Hathaway Inc., 1440 Kiewit Plaza, Omaha, NE 68131; OBH, Inc.,Warren E. Buffett, 1440 Kiewit Plaza, Omaha, NE 68131; GEICO Corporation, 1 Geico Plaza, Washington, D.C. 20076; Government Insurance Company, 1 Geico Plaza, Washington, D.C. 20076; National Indemnity Company, 3024 Harney Street, Omaha, NE 68131; OBH, Inc., 1440 Kiewit Plaza, Omaha, NE 68131 and Government Insurance Company,Plaza Investment Managers, 1 Geico Plaza, Washington, D.C. 20076. Each member of the filing groupforegoing-named individual and legal entities has shared voting and dispositive power over the 8,000,000 shares with the other members of the filing group.5,018,500 shares.

(17)(16)

ThisThe information is presented as of December 31, 2002,2003, and is based solely on a Schedule 13G/A filed with the Commission on February 3, 2003.13, 2004. These securities are owned by various clients and principals of Chieftain Capital Management, Inc. ("Chieftain"). Chieftain has both shared dispositive power and shared voting power over 11,228,800 shares. The address of Chieftain is 12 East 49th Street, New York, New York 10017.

(17)

This information is presented as of February 24, 2004, and is based solely on a letter received from T. Rowe Price Associates, Inc. ("Price Associates"). Pursuant to such letter, these securities are owned by various individual and institutional investors for which T. Rowe Price Associates Inc. ("Price Associates") serves as independent advisor with power to direct investments and/or sole power to vote the securities. Price Associates has sole voting power over 1,352,7491,172,799 shares and sole dispositive power over 7,712,4785,840,078 shares, but disclaims beneficial ownership as to all of these shares. The address of T. Rowe Price Associates, Inc. is 100 E. Pratt Street, Baltimore, Maryland 21202.

(18)

This information is presented as of November 1, 2002,December 31, 2003, and is based solely on a Schedule 13G/A filed with the Commission on November 12, 2002.March 11, 2004. Mr. Smith has sole voting and dispositive power over 803,944742,489 shares and has shared voting and dispositive power over 4,620,1204,591,770 shares with Mr. Tryforos and Mr. Vassalluzo. The address of Mr. Smith is 323 Railroad Avenue, Greenwich, Connecticut 06830.

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(19)

This information is presented as of November 1, 2002,December 31, 2003, and is based solely on a Schedule 13G/A filed with the Commission on November 12, 2002.March 11, 2004. Mr. Tryforos has sole voting and dispositive power over 33,1397,816 shares and has shared voting and dispositive power over 4,620,1204,591,770 shares with Mr. Smith and Mr. Vassalluzo. The address of Mr. Tryforos is 323 Railroad Avenue, Greenwich, Connecticut 06830.

(20)

This information is presented as of November 1, 2002December 31, 2003 and is based solely on a Schedule 13G/A filed with the Commission on November 12, 2002.March 11, 2004. Mr. Vassalluzo has sole voting and dispositive power over 20,000 shares and has shared voting and dispositive power over 4,428,1204,591,770 shares with Mr. Tryforos and Mr. Smith. The address of Mr. Vassalluzo is 323 Railroad Avenue, Greenwich, Connecticut 06830.

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Executive Compensation

        The following table provides certain information concerning compensation earned by the Chief Executive Officer and the Named Executive Officers measured as of December 31, 2002.2003.

Summary Compensation Table

(1)

Reflects the Company's matching contribution to The Iron Mountain Companies 401(k) Plan for each individual.

(2)

Mr. Delle Donne joined the Company in May 2001.

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        The following table sets forth certain information concerning the grant of options to purchase the Company's Common Stock to thethose Named Executive Officers who were granted options during the year ended December 31, 2002.2003.

Option Grants In 20022003

(1)

Potential Realizable Value is based on the assumed growth rates for an assumed ten-year option term. Five percent annual growth results in a Common Stock price per share of $50.618,$62.55, and 10% annual growth results in a Common Stock price per share of $80.601,$99.60, respectively, for such term.

18

The actual value, if any, an executive officer may realize will depend on the excess of the market price of the Common Stock over the exercise price on the date the option is exercised. There is no assurance that the value realized by an executive officer will be at or near the amounts reflected in this table.

        The following table sets forth certain information with respect to stock options during the year ended December 31, 20022003 exercised by, and the unexercised options to purchase Common Stock held by, the Named Executive Officers. Mr. Reese does not have any options.

Aggregated Option Exercises In Last Fiscal Year And Fiscal Year End Option Values

(1)

Based on a year-end value of $32.88$39.71 per share, less the exercise price.

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Equity Compensation Plan Information

        The following provides certain equity compensation plan information with respect to all of our equity compensation plans in effect as of December 31, 2002:2003:

(1)

Includes the Iron Mountain/ATSI 1995 Stock Option Plan, the Nonqualified Stock Option Plan of Pierce Leahy Corp., the 1995 Plan, the 1997 Plan and the 2002 Stock Incentive Plan.

(2)

Includes the 2002 Plan.Stock Incentive Plan and the ESPP. No new grants are being made under the 1995 Plan and 1997 Plan other than shares that become available under such plans in the future as a result of the approvallapse or cancellation of outstanding stock options under the 2002 Stock Incentive1995 Plan and the 1997 Plan.

Compensation Committee Report on Executive Compensation

        The Compensation Committee consists entirely of directors who are not employees of the Company. It is the Compensation Committee's responsibility to review, recommend and approve the Company's compensation policies and programs, including all compensation for the Chief Executive Officer and the other executive officers of the Company for the fiscal year ended December 31, 2002.2003.

        The Incentive Plan Subcommittee consists entirely of directors who are both "non-employee" directors within the meaning of Rule 16b-3 under Section 16 of the Exchange Act and "outside"

19

directors within the meaning of Section 162(m) of the Code and the regulations thereunder, so that grants of options under the 1995 Plan, the 1997 Plan and the 2002 Stock Incentive Plan to executive officers were exempt under Rule 16b-3 and generally eligible for the "performance-based" exception of Section 162(m) of the Code. The Incentive Plan Subcommittee administered the 1995 Plan, the 1997 Plan and the 2002 Stock Incentive Plan and in exercise of that function determined what grants of stock options, restricted stock and stock appreciation rights thereunder were to be made to the Chief Executive Officer and the other executive officers of the Company. The Incentive Plan Subcommittee also administered the Iron Mountain/ATSI 1995 Stock Option Plan, the Nonqualified Stock Option Plan of Pierce Leahy Corp. (although no additional grants were made under those plans), and the Executive Deferred Compensation Plan.Plan and the ESPP.

        The purpose of the 1995 Plan, the 1997 Plan, the 2002 Stock Incentive Plan and the other stock incentive plans administered by the Incentive Plan Subcommittee is to encourage key employees, directors and consultants of the Company who render services of special importance to, and who contribute materially to the success of, the Company to continue their association with the Company by providing favorable opportunities for them to participate in the ownership of the Company and in its future growth. The Incentive Plan Subcommittee made a stock option grant to Mr. Ebbighausen in 2002.

24

        The purpose of the Iron Mountain Incorporated 1998 Employee Stock Purchase Plan was, and, if approved by the shareholders, the purpose of the ESPP is to provide employees of the Company with the opportunity to acquire an equity interest in the Company by providing favorable terms for them to purchase the Company's Common Stock.

        The Executive Deferred Compensation Plan is maintained for the purpose of providing deferred compensation to a select group of management and highly compensated employees of the Company. This plan is expected to encourage the continued employment of the participating employees, whose management and individual performance are largely responsible for the success of the Company, and to facilitate the recruiting of key management and highly compensated employees required for the continued growth and profitability of the Company.

        The Compensation Committee determined the salary levels of the Company's executive officers, including the Chief Executive Officer, and other officers for fiscal year 2002,2003, and the amounts of bonuses paid in 20032004 for performance in fiscal year 2002.2003. The compensation policies implemented by the Compensation Committee, which combine base salary and incentive compensation in the form of cash bonuses and long-term stock options, are designed to achieve the operating and acquisition strategies and goals of the Company. The Compensation Committee establishes base compensation for executive officers, including the Chief Executive Officer, based upon third-party compensation surveys, taking into account the other compensation components offered by the Company, the size and complexity of the Company, the experience and expected future contributions of each executive officer and other factors. Cash bonuses for executive officers including the Chief Executive Officer, are determined after the completion of each fiscal year, based upon an evaluation of the Company's performance during the year as compared with certain fiscal goals of the Company for the year, together with each executive officer's performance during such year.year and, in the case of the Chief Executive Officer, pursuant to the 2003 Senior Executive Incentive Program (the "SEIP").

        Section 162(m) of the Code generally disallows an income tax deduction to public companies for compensation in excess of $1,000,000 paid in any year to the Chief Executive Officer or any of the four other most highly compensated executive officers, to the extent that this compensation is not "performance-based" within the meaning of Section 162(m). The Compensation Committee's general policy, subject to all then prevailing relevant circumstances, is to attempt to structure the compensation arrangements of the Company to maximize deductions for federal income tax purposes. In connection with a recent review of Mr. Reese's compensation package, the Board has approved,adopted and is recommending that the shareholders approve, the SEIP. It is anticipated that the combination of Mr. Reese's 2002 bonus (paid in 2003) and his 2003 base salary will result in the payment of

20

compensation in excess of $1,000,000 for 2003. The impact of any non-deductible amount with respect to Mr. Reese's 2003 compensation will be immaterial. If approved the SEIP will help the Companyin 2003 in part to maximize the deduction for compensation paid to Mr. Reese. With respect to Mr. Reese's bonus paid in 2004 for performance in fiscal year 2003, the Compensation Committee timely certified in writing that the performance goals and other material terms of the SEIP were satisfied. The Compensation Committee also timely established, pursuant to the SEIP, the criteria for any bonus for which Mr. Reese may be eligible in the future.2005 for performance in fiscal year 2004.

COMPENSATION COMMITTEE
ARTHUR D. LITTLE,Chairman
CONSTANTIN R. BODEN
VINCENT J. RYAN
CLARKE H. BAILEY

ADDITIONAL INFORMATION

Change of Control Arrangement

        The 1995 Plan provides for acceleration of the vesting of options and stock appreciation rights if the Company or any wholly owned subsidiary of the Company is a party to a merger or consolidation (whether or not the Company is the surviving corporation) in any transaction or series of related transactions and there is a "Limited Change of Control" of the Company. As of December 31, 2002, 2003,

25

there were 536,605309,337 unvested options under the 1995 Plan. The 1997 Plan and the 2002 Stock Incentive Plan do not contain this provision. A Limited Change of Control occurs if after the merger or consolidation (1) individuals who immediately prior to the merger or consolidation served as members of the Board no longer constitute a majority of the Board or the board of directors of the surviving corporation and (2) the voting securities of the Company outstanding immediately prior to the merger or consolidation do not represent (either by remaining outstanding or upon conversion into securities of the surviving corporation) more than 50% of the voting power of the securities of the Company or the surviving corporation immediately after the merger or consolidation.

Corporate Governance

        In response to the Sarbanes-Oxley Act of 2002 ("Sarbanes-Oxley") and corporate governance rule proposals of the NYSE, the exchange on which the Common Stock of the Company is listed, Iron Mountain has undertaken a review of its governance procedures and committees to ensure that they continue to comply with rules of the Commision and NYSE, as well as best corporate governance practices. The governance rules proposed by the NYSE have not become final, and the Commission has not yet finalized all of its expected rules under Sarbanes-Oxley. As a result, Iron Mountain is still evaluating its governance procedures and committees and considering the various changes it may make. As part of this effort, the Board has recently created the position of "lead director" to facilitate discussions among the Company's independent directors and has named Mr. Boden as lead director. Additionally, the Board has established a Nominating/Governance Committee to advise the Board regarding nominees for directorships, governance principles for the Company and other matters related to the appropriate functioning of the Board in supervising the direction, affairs and management of Iron Mountain. The Board will, during 2003, continue to evaluate its committees and processes with a view to discharging its responsibilities in compliance with best corporate practices and applicable laws and rules of the NYSE. The Company will, as appropriate, make available on its website copies of committee charters and other corporate governance documents.

Compensation Committee Interlocks and Insider Participation

        TheFor the year ended December 31, 2003, the Compensation Committee of the Board consistsconsisted of Mr. Little,Bailey, who is the Chairman, and Messrs. Boden, RyanLittle and Bailey.Ryan. Mr. Ryan is the Chairman of the Board and Chief Executive Officer of Schooner and principal shareholder of Schooner Capital Trust. Schooner is a party to a lease as described in "Certain Relationships and Related Transactions." Mr. Ryan resigned from the Compensation Committee effective March 5, 2004 so that the Compensation Committee would consist entirely of independent directors as required by NYSE listing standards.

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Certain Relationships and Related Transactions

        Schooner leases space from the Company at the Company's corporate headquarters. Vincent J. Ryan, a director of the Company, is the Chairman of the Board and Chief Executive Officer of Schooner. The lease is a tenancy-at-will and may be terminated by either the Company or by Schooner at any time. As consideration for the lease, Schooner pays rent to the Company based on its pro rata share of all expenses related to the use and occupancy of the premises. The rent paid by Schooner to the Company under such lease was approximately $128,000$143,569.73 in the year ended December 31, 2002,2003, and Schooner currently pays annual rent of approximately $144,000.$169,450. The Company believes that the terms of this lease are no less favorable to it than would have been negotiated with an unrelated third party.

        During 2002, the Company leased from three separate limited partnerships certain of its facilities in Suffield, Connecticut, Orlando, Florida and Charlotte, North Carolina. J. Peter Pierce, who resigned as a director of the Company on December 23, 2002, is the general partner of the limited partnerships, and members of the Pierce family and their affiliates own substantial limited partnership interests in each of the limited partnerships. The leases for the Suffield and Orlando facilities terminate on December 31, 2005 and January 3, 2006, respectively. The Charlotte facility was sold in 2002 to an unaffiliated party. Each of the leases for the Suffield and Orlando facilities contain two five-year renewal options. The aggregate rental payment by the Company under these leases during 2002 was $482,000. The Company believes that the terms of these leases are no less favorable to the Company than would have been negotiated with unrelated third parties.

The Company paid compensation of approximately $217,000$265,000 for the year ended December 31, 20022003 to Mr. T. Anthony Ryan. Mr. Ryan is Vice President, Real Estate, of the Company and is the brother of Vincent J. Ryan, a director of the Company. The Company believes that the terms of Mr. Ryan's employment are no less favorable to it than would be negotiable with an unrelated third party.

        The Company provided an annual pension in the amount of $96,000 to Leo W. Pierce, Sr. for the year ended December 31, 2002. Mr. Pierce formerly served as Chairman Emeritus of the Company and is the father of J. Peter Pierce, who resigned as a director of the Company on December 23, 2002. The Company will continue to provide a pension to Mr. Pierce in 2003.

Litigation with Related Parties

        On March 28, 2002, the Company and IMIM commenced an action in the Middlesex County, New Jersey, Superior Court, Chancery Division, captioned Iron Mountain Incorporated and Iron Mountain Information Management, Inc., v. J. Peter Pierce, Douglas B. Huntley, J. Michael Gold, Fred A. Mathewson, Jr., Michael DiIanni, J. Anthony Hayden, Pioneer Capital, LLC, and Sequedex, LLC. In the complaint, the Company alleges that defendant J. Peter Pierce, a former member of the Company's Board and the former President of IMIM until his termination without cause effective June 30, 2000, violated his fiduciary obligations, as well as various noncompetition and other provisions of an employment agreement with the Company, dated February 1, 2000, by providing direct and/or indirect financial, management and other support to defendant Sequedex. Sequedex was established in October 2000, and competed directly with the Company in the records and information management services industry. The complaint also alleges that Mr. Pierce and certain of the other defendants, who were employed by or affiliated with Pierce Leahy Corp. prior to the merger of Pierce Leahy with the Company in February 2000, misappropriated and used the Company's trade secrets and other confidential information. Finally, the complaint asserts claims against Sequedex and others for tortious interference with contractual relations, against all of the defendants for civil conspiracy in respect of the matters described above, and against defendant Michael DiIanni for breach of his employment agreement with IMIM, dated September 6, 2000. The litigation seeks injunctions in respect of certain matters and recovery of damages against the defendants. On April 12, 2002, the Company also initiated

22

a related arbitration proceeding against Mr. Pierce before the Philadelphia, Pennsylvania, Office of the American Arbitration Association (the "AAA") on account of an arbitration clause in the employment agreement between the Company and Mr. Pierce. In the arbitration, Mr. Pierce has counterclaimed for indemnification of his expenses, including attorneys' fees. The Company has disputed Mr. Pierce's claim. On July 19, 2002, the litigation was stayed pending the outcome of the arbitration proceeding. On February 25, 2003, in response to the Company's request, the AAA removed the arbitrator. A replacement arbitrator is in the process of being selected. The Company intends to prosecute the arbitration proceeding and the litigation vigorously.

        On December 16, 2002, Hartford Windsor Associates, L.P. ("H-W Associates"), Hartford General, LLC, J. Anthony Hayden, Mr. Pierce, Frank Seidman and John H. Greenwald, Jr. commenced an action in the Court of Common Pleas, Montgomery County, Pennsylvania, against the Company. In the complaint, the plaintiffs allege that H-W Associates purchased a warehouse property in Connecticut to serve as a records storage facility, and entered into a lease for the facility with Sequedex, then a competitor of the Company, and that the remaining plaintiffs were limited or general partners of H-W Associates. The plaintiffs also allege that the Company tortiously interfered with Sequedex's contractual relations with an actual or prospective customer of Sequedex and, as a result, caused Sequedex to default on its lease to H-W Associates. The complaint seeks damages in excess of $100,000.

        Also on December 16, 2002, Pioneer Capital L.P. ("Pioneer"), Pioneer Capital Genpar, Inc. ("PCG"), the general partner of Pioneer, and Mr. Pierce, the President of PCG, commenced an action in the Court of Common Pleas, Montgomery County, Pennsylvania, against the Company, C. Richard Reese, John F. Kenny, Jr., Garry Watzke, Schooner and Vincent J. Ryan. The named individuals are directors and/or officers of the Company and Schooner is a shareholder of the Company. In the complaint, the plaintiffs allege that the defendants had numerous conversations and arrangements with Mr. Carr, one of Mr. Pierce's and Pioneer's business partners in a company named Logisteq LLC. The plaintiffs further allege that, as a result of such conversations and arrangements, defendants conspired to, and did intentionally, interfere with Pioneer's relationship with its partner and Logisteq. The plaintiffs also allege that defendants damaged Mr. Pierce's reputation in the community by telling employees of the Company and other third parties that Mr. Pierce breached his employment agreement with the Company, misappropriated and used the Company's confidential information, breached his fiduciary duties to the Company's shareholders and assisted Sequedex, then a competitor of the Company, in unfairly competing with the Company. Finally, the complaint alleges that the business partner in Logisteq taped conversations with Mr. Pierce and others which allegedly violated privacy laws, that the defendants knew, or should have known, that the tapes were being made without the consent of the individuals and, as a result, Mr. Pierce was harmed. The complaint seeks damages in excess of $5,000,000. The Company and the other defendants have challenged the legal sufficiency of the plaintiffs' pleadings in each of these cases, and intend to vigorously defend themselves against these lawsuits.

Audit Committee Report

        Management is responsible for the Company's financial reporting process including its system of internal controls, and for the preparation of consolidated financial statements in accordance with generally accepted accounting principles. The Company's independent auditor is responsible for auditing those financial statements. The Audit Committee's responsibility is to monitor and review these processes.

        The Audit Committee has reviewed and discussed with the independent auditor and management the plan and results of the auditing engagement and the audited financial statements for the fiscal year ended December 31, 2002.2003. The Audit Committee has reviewed with management the scope and nature of the Company's internal auditing controls and has discussed with the independent auditor the matters required to be discussed by Statement on Auditing Standards No. 61, Communications with Audit

23

Committee. In addition, the Audit Committee has received the written disclosures and the letter from the independent auditor required by Independence Standards Board No. 1, Independence Discussions With Audit Committees and discussed with the independent auditor its independence from the Company and its management. The Audit Committee considered whether the provision of nonaudit

26

services by the independent auditor is compatible with maintaining the independent auditor's independence and concluded that it was acceptable at this time.

        The Audit Committee has reported to the Board its activities, conclusions and recommendations. Specifically, in reliance on the reviews and discussions referred to above, the Audit Committee recommended to the Board, and the Board has approved, that the audited financial statements be included in the Company's Annual Report on Form 10-K for the year ended December 31, 2002,2003, as filed with the Commission on March 21, 2003.11, 2004. The Audit Committee has approved the reappointment of Deloitte & Touche LLP as the Company's independent auditor for the fiscal year ending December 31, 2003.2004.

AUDIT COMMITTEE
CONSTANTIN R. BODEN,Chairman
ARTHUR D. LITTLE
KENT P. DAUTEN

Auditors

        The Company is not required to submit the selection of the Company's auditors to a shareholder vote. On June 19, 2002, the Board, upon recommendation of theMay 21, 2003, our Audit Committee and approval of the Executive Committee, dismissed Arthur Andersen LLP as the Company's independent public accountants and engaged Deloitte & Touche LLP as the Company's independent public accountants for the fiscal year ending December 31, 2002.2003.

        For a portion of fiscal year 2002, Arthur Andersen LLP acted as the Company's independent public accountants. On June 19, 2002, the Board, upon the recommendation of the Audit Committee and approval of the Executive Committee, dismissed Arthur Andersen as the Company's independent public accountants. The audit reports of Arthur Andersen on the Company's consolidated financial statements for the fiscal yearsyear ended December 31, 2000 and 2001 did not contain any adverse opinion or disclaimer of opinion, nor were they qualified or modified as to uncertainty, audit scope or accounting principles. During the two fiscal yearsyear ended December 31, 2001 December 31, 2000 and the subsequent interim period through June 19, 2002, there were no disagreements with Arthur Andersen on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedure, which disagreements, if not resolved to Arthur Andersen's satisfaction, would have caused Arthur Andersen to make reference to the subject matter of the disagreement in connection with its reports. None of the reportable events described under Item 304(a)(1)(v) of Regulation S-K occurred within the fiscal yearsyear ended December 31, 2001 December 31, 2000 or within the interim period through June 19, 2002.

        The Company provided Arthur Andersen with a copy of the above disclosures. A letter dated June 19, 2002 from Arthur Andersen stating its agreement with the Company's statements is listed under Item 7 and filed as Exhibit 16.1 and incorporated by reference into the Company's report on Form 8-K filed June 19, 2002.

        During the two fiscal yearsyear ended December 31, 2001 and 2000, and the subsequent interim period through June 19, 2002, the Company did not consult with Deloitte & Touche with respect to the application of accounting principles to a specified transaction, either completed or proposed, or the type of audit opinion that might be rendered on the Company's consolidated financial statements or regarding any other matters or events set forth in Item 304(a)(2)(i) and (ii) of Regulation S-K.

        A representative of Deloitte & Touche is expected to be present at the Annual Meeting. They will have the opportunity to make a statement if they desire to do so and will be available to respond to appropriate questions from shareholders who are present at the Annual Meeting.

The aggregatefees for services provided by Deloitte & Touche LLP to us for the fiscal year ended December 31, 2003 and fees for services provided by Deloitte & Touche for the audit of the 2002

27

financial statements and services provided by Deloitte & Touche and Arthur Andersen for reviews of the financial statements included in the Company's 2002 quarterly reports are set forth below under "Audit

24

Fees." The fees for other services provided by Deloitte & Touche to the Company during 2002 are also set forth below:were as follows:

(1)

Includes fees paid to Arthur Andersen for audit services provided in the first quarter of 2002.

(2)

Audit Related Fees include benefit plan audits, due diligence and accounting consultations.

(3)

Tax Fees include tax return preparation, compliance work and foreign jurisdiction tax consulting.

(4)

All Other Fees include employee benefits consultations and purchase of accounting software and related services.

        RepresentativesThe Audit Committee has established policies and procedures which are intended to control the services provided by our auditors and to monitor their continuing independence. Under these policies, no audit or non-audit services may be undertaken by our auditors unless the engagement is specifically pre-approved by the Audit Committee. The Audit Committee may delegate to one or more members the authority to grant the pre-approvals required by this paragraph. The decisions of any member to whom authority is delegated to pre-approve an activity under this paragraph must be presented to the full Audit Committee at each of its scheduled meetings.

        The Audit Committee may not approve performance by our auditor or its personnel of the following non-audit services for the Company (unless permitted by SEC rules and applicable accounting standards): (1) bookkeeping or other services related to the accounting records or financial statements of the Company; (2) financial information systems design and implementation; (3) appraisal or valuation services, fairness opinions, or contribution in kind reports; (4) actuarial services; (5) internal audit outsourcing services; (6) management functions or human resources; (7) broker or dealer, investment advisor, or investment banking services; and (8) legal services and expert services unrelated to the audit.

        The Audit Committee will not approve engagements of our auditors to perform non-audit services for us if doing so will cause our auditors to cease to be independent within the meaning of applicable SEC or NYSE rules. In other circumstances, the Audit Committee considers among other things, whether our auditors are able to provide the required services in a more or less effective and efficient manner than other available service providers.

        Since May 6, 2003, the date when SEC rules relating to approval of services by auditors became effective, all services for which we engaged our auditors were pre-approved by the Audit Committee. The total fees we paid to Deloitte & Touche and Arthur Andersen for services in 2002 and 2003 are set forth above. The Audit Committee approved the engagement of Deloitte & Touche are expected to be presentprovide these non-audit services because they determined that Deloitte & Touche's providing these services would not compromise its independence and that its familiarity with our record keeping and accounting systems would permit it to provide these services with equal or higher quality, quicker and at the Annual Meeting. They will have the opportunity to make a statement if they desire to do so and will also be available to respond to appropriate questionslower cost than we could obtain these services from shareholders.other providers.

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Section 16(a) Beneficial Ownership Reporting Compliance

        Section 16(a) of the Exchange Act requires that the Company's executive officers, directors, and persons who own more than ten percent of a registered class of the Company's equity securities file reports of ownership on Form 3 and changes in ownership on Form 4 or 5 with the Commission. Such executive officers, directors and ten percent shareholders are also required by Commission rules to furnish to the Company copies of all Section 16(a) reports that they file. Based solely on its review of the copies of such forms received by it, or written representations from certain reporting persons that they were not required to file a Form 5, the Company believes that, during the fiscal year ended December 31, 2002,2003, the Company's executive officers, directors and ten percent shareholders complied with all Section 16(a) filing requirements applicable to such persons, except that each of Jean A. Bua, our Chief Accounting Officer, John F. Kenny, a director Arthur D. Little, wasand our Chief Financial Officer and Robert G. Miller, President and Chief Operating Officer of IMRM, were late in filing onea report on Form 4 relating to a single transaction by The Little Family Trust,options granted to each of them of which he is a beneficiary.they were not notified in time to meet accelerated filing requirements.

2529

Performance Graph

        In February 2000, Iron Mountain merged with Pierce Leahy Corp. in a stock-for-stock merger. In order to provide comprehensive disclosure, the performance graphs for both Iron Mountain and Pierce Leahy prior to the merger are shown below, in addition to a performance graph for the combined company after the merger.

Iron Mountain—Pre-Merger

        The following graph compares the percentage change in the cumulative total return on the common stock of Iron Mountain prior to the merger to the cumulative total returns of the S&P 500 Index and the S&P Small Cap 600 Index for fiscal years 1999, 1998, 1997 and 1997.1996. This comparison assumes an investment of $100 on February 1, 1996 and the reinvestment of any dividends.

*

$100 INVESTED ON 2/1/96 IN STOCK OR ON 1/31/96
IN INDEX—INCLUDING REINVESTMENT OF DIVIDENDS.
FISCAL YEAR ENDING DECEMBER 31.

2630

Pierce Leahy

        The following graph compares the percentage change in the cumulative total return on Pierce Leahy's common stock to the cumulative total returns of the S&P 500 Index and the Russell 2000 Index for fiscal years 1999 and 1998 and for the portion of 1997 that Pierce Leahy's common stock was registered under Section 12 of the Exchange Act. This comparison assumes an investment of $100 on July 2, 1997 and the reinvestment of any dividends.

*

$100 INVESTED ON 7/2/97 IN STOCK OR INDEX—
INCLUDING REINVESTMENT OF DIVIDENDS.
FISCAL YEAR ENDING DECEMBER 31.

2731

Iron Mountain—Post-Merger

        The following graph compares the percentage change in the cumulative total return on the Common Stock of the combined Company after the merger of Iron Mountain and Pierce Leahy on February 1, 2000 to the cumulative total returns of the S&P 500 Index and the Russell 1000 Index for the period from February 1, 2000 through December 31, 2002.2003. This comparison assumes an investment of $100 on February 1, 2000 and the reinvestment of any dividends.

*

$100 INVESTED ON 2/1/00 IN STOCK OR ON 1/31/00
IN INDEX—INCLUDING REINVESTMENT OF DIVIDENDS.
FISCAL YEAR ENDING DECEMBER 31.

2832

Other Matters

        The Board does not know of any other matters that may come before the Annual Meeting. However, if any other matters are properly presented to the meeting, it is the intention of the persons named in the accompanying proxy to vote, or otherwise act, in accordance with their best judgment on such matters.

Additional Documentation

        The Company will furnish without charge to any shareholder, upon written or oral request, a copy of the Company's Annual Report on Form 10-K, including the financial statements and the financial statement schedules and other documents filed pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act. Requests for such documents should be addressed to the Secretary of Iron Mountain Incorporated, 745 Atlantic Avenue, Boston, Massachusetts 02111, telephone number (617) 535-4766.

Proposals of Shareholders

        The Company expects to hold the 2004 Annual Meeting on May 27, 2004.

        A shareholder who intends to present a proposal at the 2004 Annual Meeting of Shareholders for inclusion in the Company's 2004 proxy statement and proxy card relating to that meeting must submit the proposal by December 19, 2003. In order for the proposal to be included in the proxy statement, the shareholder submitting the proposal must meet certain eligibility standards and comply with certain procedures established by the Commission, and the proposal must comply with the requirements as to form and substance established by applicable laws and regulations. The proposal must be mailed to the Company's principal executive office, at the address stated herein, and should be directed to the attention of the Chief Financial Officer.

        A shareholder who intends to present a proposal at the 2004 Annual Meeting of Shareholders and who intends to conduct his or her own proxy solicitation must submit the proposal to the Company not earlier than January 18, 2004 and not later than February 17, 2004.

By Order of the Board of Directors,

GARRY B. WATZKE,Secretary

April 17, 200322, 2004

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Appendix A

IRON MOUNTAIN INCORPORATED

2003 EMPLOYEE STOCK PURCHASE PLANAppendix A

1.    PURPOSEAUDIT COMMITTEE
OF
IRON MOUNTAIN INCORPORATED

CHARTER

        The purposeAudit Committee (the "Committee") of the Iron Mountain Incorporated 2003 Employee Stock Purchase Plan is to provide employeesBoard of Directors (the "Board") of Iron Mountain Incorporated (the "Company") and its Subsidiaries the opportunity to acquire an equity interest in the Companyshall consist of a minimum of three (3) directors, one of whom will act as Chair. The Committee will act by providing favorable terms for them to purchase its stock. This Plan is intended to qualify as an employee stock purchase plan within the meaning of Section 423a majority of the Code.

2.    DEFINITIONS

        (a)  "Board"members present at a meeting. Meetings may be held in person or by telecommunications pursuant to which all members attending can communicate with each other. In lieu of a meeting, the Committee may act by unanimous written consent. In the event one or more vacancies on the Committee temporarily reduce the number of members to two (2), action taken by the two members of the Committee shall meanbe deemed authorized actions of the Committee. Members of the Committee shall be appointed by the Board of Directors and shall serve until the meeting of the Company.

        (b)  "ChangeBoard occurring immediately after the next following annual meeting of Control"shareholders unless they earlier resign or are removed by the Board acting in its discretion. Unless a Chair is elected by the Board, the members of the Company shall be deemed to have occurred if any person (as such term is used in Section 13(d) and 14(d)(2)Committee may designate a chair by majority vote.

I.    Purpose

        The primary purpose of the Exchange Act) other than a trust relatedCommittee is to an employee benefit plan maintained byassist the Company becomesBoard in fulfilling its responsibility to oversee the beneficial owner (withinquality and integrity of, and management's conduct with respect to, the meaning of Rule 13d-3 under the Exchange Act) of 50 percent or moreCompany's financial reporting process, including oversight of the Company's outstanding Common Stock,compliance with legal and withinregulatory requirements. This role involves:

        (a)   assisting the period of 24 consecutive months immediately thereafter, individuals other than (i) individuals who at the beginning of such period constitute the entire Board or (ii) individuals whose election, or nomination for election by the Company's shareholders, was approved by a vote of at least two-thirdsin oversight of the directors then still in office who were directors at the beginning of the period, become a majority of the Board.

        (c)  "Code" shall mean the Internal Revenue Code of 1986, as amended. Any reference to a particular Section shall include any successor and regulation thereto.

        (d)  "Committee" shall have the meaning set forth in Section 3.

        (e)  "Common Stock" shall mean the sharesintegrity of the Company's common stock, $0.01 par value per share.financial statements;

        (b)   assisting the Board in oversight of the Company's compliance with legal and regulatory requirements;

        (c)   assisting the Board in oversight of the independent auditor's qualifications and independence;

        (d)   assisting the Board in the performance of the Company's internal audit function and independent auditors;

        (e)   preparing an Audit Committee report as required by the Securities and Exchange Commission ("SEC") to be included in the annual proxy statement; and

        (f)    "Company" shall haveperforming such other duties as the meaning set forth in Section 1.

        (g)  "Compensation" shall mean cash remuneration reported (orBoard may assign to be reported) in Box 1 of Form W-2, or its equivalent, increased by any salary reduction elected pursuant to Sections 402(g), 132(f) or 125 of the Code.

        (h)  "Employee" shall mean any individual who is customarily employed for more than five months in a calendar year by the Company or any Subsidiary. The term Employee shall not include: (i) any individual who is not a common law employee of the Company or a Subsidiary; (ii) any Employee who owns, directly or indirectly, as of the Offering Date five percent or more of the total combined voting power or value of all classes of stock of the Company or a Subsidiary; (iii) any individual who is a common law employee of a Subsidiary, none of the employees of which participate in the Plan, as determined by the Committee; (iv) any Employee who is a member of a collective bargaining unit with which the Company or a Subsidiary has bargained in good faith with respect to participation in the Plan and as a result of such bargaining the labor organization made an affirmative decision not to participate in the Plan; and (v) any Employee whose employment commencement date is fewer than six months prior to the commencement of an Offering.

        (i)    "Exchange Act" shall mean the Securities Exchange Act of 1934, as amended.

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        (j)    "Exercise Date" shall mean the date(s) designated by the Committee from time to time on which an Optionee may exercise an Option; provided, however,time.

        While the Committee has the powers and responsibilities set forth in this Charter, it is not the duty of the Committee to prepare the Company's financial statements, to plan or conduct audits of those financial statements, to determine that no Exercise Datethose financial statements are complete and accurate and in accordance with generally accepted accounting principles, or to determine that disclosures have been properly made. This is the responsibility of the Company's management and the independent auditor.

II.    Duties and Responsibilities

        The Committee shall have the following duties and responsibilities:

        (a)   The Committee shall be more than 12 months afterdirectly responsible for the applicable Offering Date;appointment, compensation, retention and provided, further, that if such prior date is not a business day,oversight of the Exercise Date shall bework of the business day immediately precedingindependent auditor (including resolution of any disagreements over

A-1

financial reporting) for the applicable date.

        (k)  "Fair Market Value" shall be determined accordingpurpose of preparing or issuing an audit report or performing other audit review or test services, and the independent auditor must report to the following rules:Committee.

        (b)   The Committee shall establish procedures for:

        (i)    if the Common Stock is notreceipt, retention and treatment of complaints received by the Company regarding accounting, internal accounting controls, or auditing matters; and

        (ii)   the confidential, anonymous submission by Company employees of concerns regarding questionable accounting or auditing matters.

        (c)   The Committee shall at least annually review a report by the time listedCompany's independent auditor describing the auditor's internal control procedures, any material issues raised by the auditor's most recent quality control review, and assessment of all material relationships between the independent auditor and the Company;

        (d)   The Committee shall discuss the Company's annual and quarterly financial statements with management and the independent auditor (including disclosures under management's discussion and analysis of financial condition and results of operations ("MD&A"));

        (e)   The Committee shall discuss earnings press releases (either individually or admittedgenerally) with management, as well as financial information and earnings guidance provided to trading on a stock exchangeanalysts and ratings agencies;

        (f)    The Committee shall periodically discuss with management policies with respect to risk assessment and risk management;

        (g)   The Committee shall periodically hold separate meetings with management, internal auditors and the independent auditor;

        (h)   The Committee shall review with the independent auditor any audit problems or difficulties and management's responses;

        (i)    The Committee shall set policies regarding the Nasdaq National Market, Fair Market Value shall be the closing pricehiring of employees or former employees of the Common Stock on the date in question in the over-the-counter market, as such price is reported in a publication of general circulation selected by the Boardindependent auditor; and regularly reporting the price of the Common Stock in such market; provided, however, that if the price of the Common Stock is not so reported, Fair Market Value

        (j)    The Committee shall be determined in good faith by the Board, which may take into consideration (1) the price paid for the Common Stock in the most recent trade of a substantial number of shares knownfurnish regular reports to the Board to have occurred at arm's length between willingconcerning the Committee's work.

III.    Membership Qualifications

        All of the members of the Committee shall meet the independence requirements of the SEC, the Corporate Governance Rules of the New York Stock Exchange ("NYSE") listing standards and knowledgeable investors, (2) an appraisal by an independent party or (3) any other methodapplicable laws and regulations. At least one member of valuation undertaken in good faiththe Committee shall be an audit committee financial expert, as such term is defined by the Board, or some orSEC; all members of the above as the Board shall in its discretion elect; or (ii) if the Common Stock is at the time listed or admitted to trading on any stock exchange or the Nasdaq National Market, then Fair Market ValueCommittee shall be the mean between the lowest and highest reported sale prices (or the lowest reported bid price and the highest reported asked price) of the Common Stock on the date in question on the principal exchange on which the Common Stock is then listed or admitted to trading. If no reported sale of Common Stock takes place on the date in question on the principal exchange or the Nasdaq National Market,"financially literate," as the case may be, then the reported closing sale price (or the reported closing asked price) of the Common Stock on such date on the principal exchange or the Nasdaq National Market, as the case may be, shall be determinative of Fair Market Value.

        (l)    "Insider" shall mean a person subject to Section 16 of the Exchange Act.

        (m)  "Offering" shall mean any offering of Common Stock in accordance with Section 7.

        (n)  "Offering Date" shall mean the date(s) designateddefined by the Committee fromNYSE, or shall become financially literate within a reasonable period of time to time on which an Option is granted; provided, however, that there shall beafter their appointment; and at least one Offering Date in any consecutive 12-month period whilemember of the Plan remains in effect; and provided, further, that if such date is not a business day, the Offering Date shall be the business day immediately preceding the applicable date.

        (o)  "Option" shall mean the right of a Participant to purchase Common Stock pursuant to an Offering.

        (p)  "Option Price"Committee shall have accounting or related financial management expertise within the meaning set forth in Section 8.

        (q)  "Optionee" shall mean any individual who has been granted an Option that remains outstanding under the terms of any Offering or who owns Common Stock as a result of an Offering.

        (r)  "Participant" shall mean an Employee who has in effect a payroll deduction authorization in accordance with Section 6.

        (s)  "Plan" shall mean the Iron Mountain Incorporated 2003 Employee Stock Purchase Plan as set forth herein, with any and all amendments hereto that may be in effect.

        (t)    "Securities Act" shall mean the Securities Act of 1933, as amended.

        (u)  "Subsidiary" shall mean a corporation of which the Company owns, directly or indirectly through an unbroken chain of ownership, fifty percent or more of the total combined voting power of all classes of stock, whether or not such corporation now exists or is hereafter organized or acquired by the Company or a Subsidiary. An entity may be treated as a Subsidiary for purposes of this Plan if, consistent with Sections 423 and 424Corporate Governance Rules of the Code, such entity is owned by a corporation and is

A-2

disregarded for federal income tax purposes, or such entity is treated as a corporation for federal income tax purposes.

3.    ADMINISTRATION OF THE PLAN

        Unless the Board shall designate another person or persons, the Plan shall be administered by the Stock Incentive Plan Subcommittee (the "Committee") of the Compensation Committee of the Board.NYSE listing standards. No member of the Committee shall be liablea member of the audit committee of more than three publicly held companies unless the Board shall have determined that such simultaneous service does not impair the ability of such member to serve on the Committee.

        No member of the Committee shall (a) directly or indirectly receive from the Company consulting, advisory or other compensatory fees other than Board or Committee fees or similar compensation for serving on the Board or a committee of the Board; or (b) be an "affiliated person" (as defined by SEC rules and regulations) of the Company or any actionsubsidiary thereof, unless permitted by an exemption provided by such rules and regulations. The Company shall make required disclosure of any exception in its annual proxy statement.

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IV.    Periodic Reviews and Other Activities

        The following functions shall be the regular recurring activities of the Committee in carrying out its oversight function and its responsibilities. These functions are set forth as a guide with the understanding that the Committee may diverge from this guide as appropriate given the circumstances.

        (a)   Quarterly, in connection with the preparation of each periodic report of the Company, the Committee shall review with management and the independent auditor:

          (i)  The Company's financial statements, including the Company's disclosures under MD&A, to be included in the Company's periodic reports, prior to the filing of such reports with the SEC. Such review shall specifically include a discussion with management regarding:

        (A)  Critical accounting estimates and judgments including how policies were chosen among alternatives, the methodology of applying those estimates and policies, and the assumptions made, and the impact of changes in, those policies, both qualitatively and quantitatively;

        (B)  Material off-balance sheet transactions, arrangements, obligations (including contingent obligations) and other relationships of the Company with unconsolidated entities or determinationother persons, that may have a material current or future effect on financial condition, changes in financial condition, results of operations, liquidity, capital resources, capital reserves or significant components of revenues or expenses; and

        (C)  Related-party transactions.

         (ii)  Any analysis prepared by management and/or the independent auditor of significant financial reporting issues and judgments made in good faithconnection with the preparation of such financial statements, including analyses of the effects of the application of alternative generally accepted accounting principles ("GAAP") on the financial statements.

        (b)   Quarterly, in connection with the preparation of each periodic report of the Company, the Committee shall review: (i) management's disclosures to the Committee under Section 302 of the Sarbanes-Oxley Act and (ii) the CEO and CFO certifications to be filed pursuant to Sections 302 and 906 of the Sarbanes-Oxley Act, and the bases therefor.

        (c)   At least quarterly, the Committee shall meet, separately, with management, the internal auditing staff, and the independent auditor to review and discuss the Company's auditing and accounting principles and practices and financial statement presentations that could significantly affect the Company's financial statements, any changes in the Company's selection or application of accounting principles suggested by the independent auditor, internal auditing staff or management and any major issues as to the quality and adequacy of the Company's internal controls.

        (d)   At least annually, the Committee shall obtain and review a report by the independent auditor describing: (i) the firm's internal quality-control procedures; and (ii) any material issues raised by (a) the most recent internal quality-control review, or peer review, of the firm, or (b) any inquiry or investigation by governmental or professional authorities, within the preceding five (5) years, respecting one (1) or more independent audits carried out by the firm, and any steps taken to deal with any such issues. In addition, the Committee shall verify that the independent auditor is registered with the Public Company Accounting Oversight Board ("PCAOB"), review any public reports of the PCAOB disciplining the independent auditor and review any recent inspection reports of the independent auditor.

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        (e)   In connection with any audit, the independent auditor shall inform the Committee about:

          (i)  All critical accounting policies, alternative GAAP methods or departures from GAAP discussed with management and their ramifications, and the independent auditor's preferred alternative; and

         (ii)  Other material written communications between the independent auditor or its firm and management, such as any management letter or schedule of unadjusted differences.

        (f)    At least annually, the Committee shall evaluate the independence of the independent auditor by:

          (i)  Discussing with the independent auditor any relationships between the independent auditor and the Company (consistent with Independence Standards Board Standard No. 1) and their impact on the independent auditor's independence;

         (ii)  Considering whether there should he a rotation of the audit firm in order to ensure auditor independence; and

        (iii)  Confirming that the lead (or coordinating) audit partner (the audit partner having primary responsibility for the audit) has not performed audit services for the Company for each of the past five (5) fiscal years, and that other audit partners have not performed services for the Company for such periods of time as would be prohibited by SEC rules or applicable accounting standards. The Committee shall also review and evaluate the lead audit partner.

        (g)   The Committee shall prepare the report required by the SEC to be included in the Company's annual proxy statement and review and approve all other disclosures regarding the Committee and the performance of its duties to be included in such proxy statement or in any other document required by applicable securities laws or stock exchange listing requirements or rules;

        (h)   The Committee shall regularly review with the independent auditor:

          (i)  Any problems or difficulties encountered in the course of the audit work, including any restrictions on the scope of the activities or access to requested information, and the Company's response;

         (ii)  Any disagreements with management;

        (iii)  Any changes required in the planned scope of the internal audit; and

        (iv)  The internal audit department responsibilities, budget and staffing.

        (i)    Periodically, the Committee shall meet with management to review the Company's major financial risk exposures and the steps management has taken to monitor and control such exposures, and to discuss guidelines and policies to govern the process by which risk assessment and management is undertaken. This review must include a discussion of any significant deficiencies and material weaknesses or other major adequacy issues in the design or operation of internal control over financial reporting and any fraud (without regard to materiality) involving management or employees with a significant role in the Company's internal control over financial reporting. The Committee shall discuss any special steps adopted in light of material control deficiencies.

        (j)    Periodically, the Committee shall review with management, the independent auditor, the internal auditing staff and the Company's counsel, as appropriate, any legal, regulatory or compliance matters (including any material reports or inquiries received from regulators or governmental agencies) that could have a significant impact on the Company's financial statements, including significant changes in accounting standards or rules as promulgated by the PCAOB, the Financial Accounting Standards Board, the SEC or other regulatory authorities with relevant jurisdiction.

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        (k)   The Committee shall discuss the general contents of earnings press releases (including the use of "pro forma" or "adjusted" or other non-GAAP information), as well as financial information and earnings guidance provided to analysts and rating agencies.

        (l)    The Committee shall preapprove all audit (including comfort letters and statutory audits) and non-audit services, other than as provided in the following sentence. The preapproval requirement is waived with respect to the Plan.provision of non-audit services for the Company, if:

          (i)  The aggregate amount of all such non-audit services provided to the Company constitutes no more than five percent (5%) of the total amount of revenues paid by the Company to the independent auditor during the fiscal year in which the non-audit services are provided;

         (ii)  Such services were not recognized by the Company at the time of the engagement to be non-audit services; and

        (iii)  Such services are promptly brought to the attention of the Committee and approved prior to the completion of the audit by the Committee or by one or more members of the Committee to whom authority to grant such approvals has been delegated by the Committee.

        The Committee may delegate to one or more members the authority to grant the preapprovals required by this paragraph. The decisions of any member to whom authority is delegated to preapprove an activity under this paragraph shall be presented to the full Committee at each of its scheduled meetings.

        The Committee's policies and procedures for such approvals of audit and non-audit services, and any waivers of approvals pursuant to the foregoing prohibitions, shall be disclosed in, or included with, the Company's annual proxy statement and annual report filed with the SEC.

        The Committee may not approve performance by the independent auditor or its personnel of the following non-audit services for the Company (unless permitted by SEC rules and applicable accounting standards): (1) bookkeeping or other services related to the accounting records or financial statements of the Company; (2) financial information systems design and implementation; (3) appraisal or valuation services, fairness opinions, or contribution in kind reports; (4) actuarial services; (5) internal audit outsourcing services; (6) management functions or human resources; (7) broker or dealer, investment advisor, or investment banking services; and (8) legal services and expert services unrelated to the audit.

        (m)  The (i) Committee shall determine the appropriate funding for payment of compensation (1) to the independent auditor for the purpose of rendering or issuing an audit report or any other services provided by the independent auditor; and (ii) to any advisors retained by the Committee to assist in carrying out its duties.

        (n)   The Committee shall review and consider with the independent auditor the matters required to be discussed by Statement of Auditing Standards No. 61.

        (o)   The Committee hereby establishes a policy that the Company may not hire employees or former employees of the independent auditor if their status as employees would cause an independent director to cease being an independent director under NYSE listing standards or SEC rules and regulations or would cause the independent auditor to cease being independent under applicable SEC rules and regulations or the standards of the PCAOB.

        (p)   The Committee shall review and consent to the appointment and replacement of the Company's senior internal audit director, approve the annual internal audit plan, and annually review the performance of the internal auditing staff.

        (q)   The Committee shall review the significant reports to management prepared by the internal auditing staff or the independent auditor, respectively, and management's responses.

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        (r)   The Committee shall at least annually review this Charter and propose to the Board any amendments it deems appropriate.

V.    Meetings

        The Committee shall meet four (4) times per year on a quarterly basis, or more frequently as circumstances require. The Committee may ask members of management, the internal auditing staff, the independent auditor and others to attend Committee meetings and to provide pertinent information, as necessary. The Committee shall meet in separate executive sessions with management, the internal auditing staff and the independent auditor to discuss any matters that the Committee (or any of these groups) believes should be discussed privately.

VI.    Subcommittees

        The Committee shall have the authority to adopt, amend and rescind such rules and regulationsdelegate any of its responsibilities to subcommittees as the Committee may deem appropriate in its opinion, may be advisable in the administration of the Plan. All questions of interpretation and application of such rules and regulations, of the Plan and of Options granted thereunder shall be subject to the determination of the Committee, which shall be final and binding.sole discretion.

VII.    Miscellaneous

        The Committee shall have the authority without the need for further approval, to establish a different Offering Date and/retain independent legal, accounting or Exercise Date,other consultants to modify the amount of time between an Offering Dateassist and an Exercise Date, to increase or decrease the number of Offerings in a year and to limit the number of shares that may be available in an Offering.

        With respect to Insiders, transactions under the Plan are intended to comply with all applicable conditions of Rule 16b-3 or its successor under the Exchange Act. To the extent any provision of the Plan or action byadvise the Committee fails to so comply, it shall be deemed to be modified so as to be in compliance with such Rule or, if such modification is not possible, it shall be deemed to be null and void, to the extent permitted by law and deemed advisable by the Committee.

4.    OPTION SHARES

        The total amount of Common Stock with respect to which Options may be granted under the Plan shall not exceed in the aggregate 750,000 shares from either authorized but unissued shares or treasury shares; provided, however, that such aggregate numberperformance of shares shall be subject to adjustment in accordance with Section 15. If any outstanding Option expires for any reason, including a withdrawal pursuant to Section 10, or terminates by reason of the severance of employment of the Participant or any other cause, or is surrendered, the shares of Common Stock allocable to the unexercised portion of the Option may again be made subject to an Option under the Plan.

5.    ELIGIBILITY

        An Employee shall be eligible to become a Participant in the Plan on any Offering Date on which the Employee is employed by the Company or a Subsidiary; provided, however, that no Employee shall be granted an Option:

          (i)  if immediately after the grant the aggregate amount of stock the Employee would be considered to own under Section 424(d) of the Code, including stock that may be purchased with outstanding options, would represent five percent or more of the total combined voting power or value of all classes of capital stock of the Company or of any Subsidiary; or

        (ii)  that permits the Employee's right to purchase shares under all employee stock purchase plans (within the meaning of Section 423 of the Code) of the Companyits purposes, duties and its Subsidiaries to accrue at a rate that exceeds $25,000 for any calendar year, determined by reference to the Fair Market Value of the shares at the time any Option is granted.

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6.    PARTICIPATION

        (a)  An Employee may become a Participant in any Offering by completing an authorization for payroll deductions in connection with the Offering at such time (prior to the Offering Date) and in such manner as the Committee may prescribe. Payroll deductions pursuant to an authorization shall commence with the payroll period in which the Offering Date occurs and shall end with the last payroll completed prior to the Exercise Date for the Offering to which the authorization applies, unless the authorization is sooner terminated by the Participant as provided in Section 10. The Committee may provide that in the case of the first Offering, payroll deductions shall commence with the first payroll period ending after the initial Offering Date. All payroll deductions shall be made on an after-tax basis.

        (b)  A Participant shall elect in the authorization for payroll deduction to have deductions made from his or her Compensation on each payday in an amount equal to a whole percentage of from one to 15 percent of his Compensation. All payroll deductions made for a Participant shall be credited to a bookkeeping account maintained for such Participant under the Plan. In no event shall interest be paid to a Participant with respect to payroll deductions credited to the Participant's account, whether such deductions are used in connection with the exercise of an Option or are returned to the Participant or the Participant's estate in cash.

        (c)  Except as may be required by law, a Participant may not make any payments to the Participant's account other than by authorization for payroll deduction. A Participant may elect to decrease the payroll deduction rate at such time and in such manner as the Committee may prescribe. In no event shall a Participant increase the amount of payroll deductions during an Offering. A Participant may discontinue participation in the Offering as provided in Section 10.

7.    GRANT OF OPTIONS

        (a)  Options under the Plan shall be granted in a series of Offerings, the first of which shall begin on the first Offering Date designated by the Committee. Successive Offerings shall begin on each Offering Date thereafter until all of the shares of Common Stock available under the Plan are exhausted or until the Plan is terminated pursuant to Section 18 or Section 19. Participation by an Employee in any Offering shall neither limit nor require his participation in any other Offering.

        (b)  Each Participant in an Offering shall be granted, as of the applicable Offering Date, an Option to purchase that number of shares of Common Stock that the accumulated payroll deductions credited to his account during the Offering are able to purchase at the Option Price.

        (c)  If the total number of shares for which Options are to be granted as of any Offering Date exceeds the number of shares available for the Offering, the Committee shall make a pro rata allocation of the available shares in a manner as nearly uniform as practicable, and as it shall determine to be equitable. Further, any accumulated payroll deductions remaining in a Participant's account after the close of such Offering shall be paid in cash to the Participant and shall not be applied to a subsequent offering. In the event a shortfall in shares appears likely, the Committee may, but shall not be required to, reduce remaining payroll deductions to be made pursuant to authorizations for that Offering.

        (d)  In no event shall a Participant be granted an Option in any Offering to acquire more than that number of shares of Common Stock equal to $25,000 divided by the Fair Market Value of the shares as of the Offering Date; provided, however, that such limit shall be subject to Section 5(ii) and to the adjustment in accordance with Section 15.

8.    OPTION PRICE

        The Option Price of shares of Common Stock for any Offering shall be the lesser of: (a) 85 percent of the Fair Market Value of the shares on the Offering Date; or (b) 85 percent of the

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Fair Market Value of the shares on the Exercise Date.responsibilities. The Committee shall have sole authority to approve related fees and retention terms.

        The Committee shall report its actions and recommendations to the authority, withoutBoard after each Committee meeting and shall conduct and present to the need for further approval and solely with respect toBoard an Offering not yet commenced, to reduce (or eliminate entirely) the amountannual performance evaluation of the 15 percent discount or may require that any discount be applied only to the Fair Market Value of the shares on the Exercise Date.Committee.

9.    EXERCISE OF OPTIONSAdopted: June 1, 2000

        (a)  A Participant's Option for an Offering will be exercised automatically as of the Exercise Date for the Offering to purchase that number of shares of Common Stock equal to the accumulated payroll deductions credited to the Participant's account as of the Exercise Date divided by the Option Price.

        (b)  A Participant may elect prior to the Exercise Date at such timeAmended and in such manner as the Committee may prescribe to receive in cash an amount equal to the accumulated payroll deductions in his account on the Exercise Date, rather than exercising his Option.

        (c)  As promptly as practicable after each Exercise Date the Company shall deliver to each Participant in the Offering, in accordance with the Participant's election, either (a) the shares purchased upon the exercise of the Participant's Option, together with a cash payment equal to the balance of any payroll deductions credited to the Participant's account during the Offering that were not used for the purchase of shares, or (b) a cash payment equal to the total of the payroll deductions credited to the Participant's account during the Offering.

        (d)  The shares purchased upon exercise of an Option shall be deemed to be transferred to the Participant on the Exercise Date.

        (e)  The Committee may, in its discretion, limit the shares purchased in an Offering to whole shares, in which event amounts representing fractional shares may, at the discretion of the Committee, either be carried forward for use in the next Offering if the Participant will participate in that Offering or paid to the Participant in cash.

10.  WITHDRAWAL FROM OFFERING

        A Participant may at any time prior to the Exercise Date at such time and in such manner as the Committee may prescribe withdraw from an Offering and request payment of an amount in cash equal to the accumulated payroll deductions credited to the Participant's account under the Plan. Such amount will be paid to the Participant as promptly as practicable after receipt of the Participant's request to withdraw, and no further payroll deductions will be made from the Participant's Compensation with respect to the Offering then in progress and any outstanding Option shall be cancelled. A Participant's withdrawal from an Offering will have no effect upon his or her eligibility to participate in any subsequent Offering or in any employee stock purchase plan (within the meaning of Section 423 of the Code) that may hereafter be adopted by the Company or a Subsidiary.

11.  EXPIRATION OF OPTIONS ON TERMINATION OF EMPLOYMENT

        (a)  Options shall not be transferable by a Participant and no amount credited to a Participant's account may be assigned, transferred, pledged or otherwise disposed of in any way by a Participant. An Option shall expire unexercised immediately if a Participant ceases to satisfy the definition of the term Employee for any reason other than death and the amount of the accumulated payroll deductions then credited to the Participant's account under the Plan will be paid in cash. Upon termination of the Participant's employment with the Company or a Subsidiary for any reason other than death, an amount in cash equal to the accumulated payroll deductions then credited to the Participant's account under the Plan will be paid to the Participant. In the case of a Participant's death, the provisions of Section 16 shall control.

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        (b)  An authorized leave of absence or absence on military or government service shall not constitute severance of the employment relationship between the Company or Subsidiary and the Participant for purposes of this Section 11, provided that either (a) the absence is for a period of no more than 90 days or (b) the Employee's right to be re-employed after the absence is guaranteed either by statute or by contract.

12.  REQUIREMENTS OF LAW

        The Company shall not be required to sell or issue any shares of Common Stock under the Plan if the issuance of such shares would constitute or result in a violation by the Optionee or the Company of any provision of any law, statute or regulation of any governmental authority. Specifically, in connection with the Securities Act, upon the exercise of any Option the Company shall not be required to issue shares unless the Board has received evidence satisfactory to it to the effect that the Optionee will not transfer such shares except pursuant to a registration statement in effect under the Securities Act or unless an opinion of counsel satisfactory to the Company has been received by the Company to the effect that such registration is not required. Any determination in this connection by the Board shall be final, binding and conclusive. The Company shall not be obligated to take any affirmative action to cause the exercise of an Option or the issuance of shares pursuant to an Option to comply with any laws or regulations of any governmental authority including, without limitation, the Securities Act or applicable state securities laws.

13.  NO RIGHTS AS SHAREHOLDER

        No Participant shall have rights as a shareholder with respect to shares covered by his Option until the applicable Exercise Date and, except as otherwise provided in Section 15, no adjustment shall be made for dividends of which the record date precedes the applicable Exercise Date.

14.  FORFEITURE FOR DISHONESTY

        Notwithstanding anything to the contrary in the Plan, if the Board determines, after full consideration of the facts presented on behalf of both the Company and the individual, that a Participant or an Optionee has been engaged in fraud, embezzlement, theft, commission of a felony or proven dishonesty in the course of his employment by the Company or a Subsidiary, which damaged the Company or Subsidiary, or has disclosed trade secrets or other proprietary information of the Company or a Subsidiary, (a) such individual's participation in an Offering shall terminate and he shall forfeit his right to receive any Common Stock pursuant to an Offering that has not yet been delivered and (b) the Company shall have the right to repurchase all or any part of the shares of Common Stock acquired by an Optionee upon the earlier exercise of any Option, at a price equal to the amount paid to the Company upon such exercise, increased by an amount equal to the interest that would have accrued in the period between the date of exercise of the Option and the date of such repurchase upon a debt in the amount of the exercise price, at the prime rate(s) announced from time to time during such period in the Federal Reserve Statistical Release Selected Interest Rates. The decision of the Board as to the cause of a Participant's or Optionee's discharge and the damage done to the Company or a Subsidiary shall be final, binding and conclusive. No decision of the Board, however, shall affect in any manner the finality of the discharge of a Participant or Optionee by the Company or a Subsidiary.

15.  CHANGES IN THE COMPANY'S CAPITAL STRUCTURE

        (a)  If the outstanding shares of Common Stock are hereafter changed for a different number or kind of shares or other securities of the Company, by reason of a reorganization, recapitalization, exchange of shares, stock split, combination of shares or dividend payable in shares or other securities, a corresponding adjustment shall be made by the Committee in the number and kind of shares or other securities, and in the Option Price, covered by outstanding Options, and for which Options may beRestated: March 4, 2004

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granted under the Plan; provided, however, that no adjustment shall be made that would constitute a modification as defined in Section 424 of the Code. Any such adjustment made by the Committee shall be conclusive and binding upon all affected persons, including the Company and all Participants and Optionees.

        (b)  If while unexercised Options remain outstanding under the Plan the Company merges or consolidates with a wholly-owned subsidiary for the purpose of reincorporating itself under the laws of another jurisdiction, the Optionees will be entitled to acquire shares of Common Stock of the reincorporated company upon the same terms and conditions as were in effect immediately prior to such reincorporation (unless such reincorporation involves a change in the number of shares or the capitalization of the Company, in which case proportional adjustments shall be made as provided above), and the Plan, unless otherwise rescinded by the Board, will remain the Plan of the reincorporated company.

        (c)  Except as otherwise provided in (a) or (b) above, if while unexercised Options remain outstanding under the Plan the Company merges or consolidates with one or more corporations (whether or not the Company is the surviving corporation), or is liquidated or sells or otherwise disposes of substantially all of its assets to another entity, or upon a Change of Control, then the Committee, in its discretion, shall provide that either:

          (i)  after the effective date of such merger, consolidation, liquidation, sale or Change of Control, as the case may be, each Optionee shall be entitled, upon exercise of an Option to receive in lieu of shares of Common Stock the number and class of shares of such stock or other securities to which he would have been entitled pursuant to the terms of the merger, consolidation, liquidation, sale or Change of Control if he had been the holder of record of the number of shares of Common Stock as to which the Option is being exercised immediately prior to such merger consolidation, liquidation or sale; or

        (ii)  all outstanding Options shall be exercised as of the day preceding the effective date of any such merger, consolidation, liquidation, sale or Change of Control, which day shall be the Exercise Date for purposes of the Offering; provided, however, that each Optionee shall be notified of the right to withdraw from the Offering in accordance with the requirements of Section 10.

        (d)  Except as expressly provided to the contrary in this Section 15, the issuance by the Company of shares of stock of any class for cash or property or for services, either upon direct sale or upon the exercise of rights or warrants, or upon conversion of shares or obligations of the Company convertible into such shares or other securities, shall not affect the number, class or price of shares of Common Stock then subject to outstanding Options.

16.  DISPOSITION OF ACCOUNT AT DEATH

        In the event that a Participant dies after the Exercise Date but before the delivery of the stock certificates, such certificates when issued together with any cash remaining in the Participant's account shall be transferred to the Participant's estate. In the event that a Participant dies prior to the Exercise Date, a payment shall be made to the Participant's estate of an amount in cash equal to the accumulated payroll deductions credited to the Participant's account under the Plan.

17.  MISCELLANEOUS

        (a)  Accumulated payroll deductions and the proceeds from the sale of shares pursuant to the exercise of Options shall constitute general funds of the Company.

        (b)  To the extent required by law, the Company or a Subsidiary shall withhold or cause to be withheld income and other taxes with respect to any income recognized by an Optionee by reason of

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the exercise of an Option. An Optionee shall agree that if the amount payable to him by the Company and any Subsidiary in the ordinary course is insufficient to pay such taxes, then he shall upon request of the Company pay to the Company an amount sufficient to satisfy its tax withholding obligations.

        (c)  All notices or other communications by a Participant or Optionee to the Company pursuant to the Plan shall be deemed to have been given when received in the form specified by the Company at the location or by the person designated by the Company for the receipt thereof.

        (d)  Neither the Plan nor the grant of an Option pursuant to the Plan shall impose upon the Company or a Subsidiary any obligation to employ or continue to employ any Participant, and the right of the Company or a Subsidiary to terminate the employment of any person shall not be diminished or affected by reason of the fact that an Option has been granted to him.

        (e)  The title of the sections of the Plan are included for convenience only and shall not be construed as modifying or affecting their provisions. The masculine gender shall include both sexes; the singular shall include the plural and the plural the singular unless the context otherwise requires.

        (f)    The Plan shall be governed by and construed in accordance with the laws of the Commonwealth of Massachusetts, without regard to the principles of conflicts of law.

18.  AMENDMENT OR TERMINATION OF PLAN

        The Board may at any time terminate or from time to time amend, modify or suspend this Plan (or any part thereof); provided, however, that without approval by an affirmative vote of a majority of the votes properly cast at a duly held meeting of the shareholders of the Corporation at which a quorum representating a majority of all outstanding Common Stock is present, in person or by proxy there shall be no: (a) change in the number of shares of Common Stock that may be issued under the Plan, except by operation of the provisions of Section 15; (b) change in the class of persons eligible to participate in the Plan; or (c) other change in the Plan that requires shareholder approval under applicable law. Notwithstanding the preceding sentence, the Board shall in all events have the power to make such changes in the Plan and the Committee shall in all events have the power to make such changes in the regulations and administrative provisions under the Plan or in any outstanding Option as, in the opinion of counsel for the Company, may be necessary or appropriate from time to time to enable the Plan to qualify as an employee stock purchase plan as defined in Section 423 of the Code, so as to enable any Option to receive preferential federal income tax treatment. No amendment shall materially affect outstanding Options without the consent of the Optionee and the termination of the Plan will not terminate Options then outstanding, without the consent of the Optionee.

        Notwithstanding the foregoing, at such time after the Company is not required to file periodic reports under the Exchange Act, at its option, the Company may terminate the Plan and, upon the termination, outstanding Options shall be cancelled and each Participant shall receive in cash an amount equal to the accumulated payroll deductions without interest credited to the Participant's account under the Plan immediately prior to termination.

19.  EFFECTIVE DATE AND DURATION OF THE PLAN

        The Plan shall be effective as of April 7, 2003, subject only to ratification by the holders of a majority of the outstanding shares of common stock present, or represented, and entitled to vote thereon (voting as a single class) at a duly held meeting (or written consents in lieu thereof) of the shareholders of the Company within 12 months before or after such date. Unless the Plan shall have terminated earlier, the Plan shall terminate on the date as of which there are no longer any shares available pursuant to Section 4 to be offered and no Option shall be granted pursuant to the Plan after that date.

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Appendix B

Appendix B

FIRST AMENDMENT TO THE IRON MOUNTAIN INCORPORATED
2003 SENIOR EXECUTIVE2002 STOCK INCENTIVE PROGRAM
PLAN

        1.    Participant.    The sole participant in this Program shall be C. Richard Reese, ChairmanAs adopted by resolution of the Board and Chief Executive Officer.

        2.    Annual Limit on Incentive Compensation.    The maximum amount payable under this Program with respect to a fiscal year shall be the lesser of 2.5 times Mr. Reese's annual base compensation for the fiscal year or $2,500,000.00 (the "Annual Limit").

        3.    Eligibility for Incentive Compensation.    While the outcome for the Corporation's fiscal year to which the incentive compensation relates is substantially uncertain (but not more than 90 days after the start of that fiscal year), the Compensation Committee of the
Board of Directors shall establishon March 4, 2004
and submitted for approval by the criteria for the paymentShareholders on May 27, 2004

1.

Section 3 of the Annual Limit. Such criteria may be based on any one or moreIron Mountain Incorporated 2002 Stock Incentive Plan (the "2002 Plan") is amended by deleting the number "1,352,543" and inserting therefor "3,352,543."

2.

Except as hereinabove amended, the provisions of the following business criteria: EBITDA; gross revenues; growth rate; capital spending; return on investment capital; free cash flow; operating income; attaining budget;2002 Plan shall remain in full force and achievement of stated corporate goals including, but not limited to acquisitions, alliances, joint ventures and internal expansion. Any such criteria shall be adjusted as necessary to reflect acquisitions. If such objectives are not fully achieved, the Compensation Committee may provide that less than 100 percent of the Annual Limit shall be payable.

        Following the close of the fiscal year, the Compensation Committee shall certify whether such criteria were satisfied.

        4.    Discretion to Reduce Incentive Compensation.    The Compensation Committee, after consultation with the Chairs of the Audit and Executive Committees of the Board of Directors, may, in its discretion, reduce the amount of incentive compensation otherwise payable for the fiscal year based on any of the following criteria: extent to which the objective financial measurements achieved for the fiscal year satisfied the Corporation's short-term or long-term goals; shareholder confidence in the Corporation, as evidenced in part by the Corporation's stock price; and the effectiveness and wellness of the Corporation as a whole, taking into account, for example, labor relations and other similar matters.

        5.    Effective Date; Right to Amend and Terminate.    This 2003 Senior Executive Incentive Program shall be effective as of March 31, 2003 and shall be first applicable for the fiscal year that begins January 1, 2003; provided, however, that the material terms of this Program must be approved prior to any payment hereunder by an affirmative vote of a majority of the votes properly cast at a duly held meeting of the shareholders of the Corporation at which a quorum representating a majority of all outstanding common stock is present, in person or by proxy.

        The Program shall continue until terminated by the Board of Directors. The Board of Directors reserves the right to from time to time amend, modify or suspend this Program (or any part thereof).

        6.    Administration.    This Program shall be construed and administered in such a manner as to permit payments hereunder to satisfy the "performance-based" exception of Internal Revenue Code Section 162(m), and regulations and rulings promulgated thereunder ("Section 162(m)"). In the event that one or more members of the Compensation Committee are not "outside directors" within the meaning of Section 162(m), the duties of the Compensation Committee as set forth herein shall be performed by a committee or subcommittee of the Board of Directors consisting solely of two or more such "outside directors."

effect.

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PROXY

IRON MOUNTAIN INCORPORATED

745 ATLANTIC AVENUE
BOSTON, MASSACHUSETTS 02111

THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS

        The undersigned hereby appoints C. RICHARD REESE and JOHN F. KENNY, JR., and each of them, as proxies of the undersigned, each with the power to appoint his substitute, and hereby authorizes both of them, or either one if only one be present, to represent and to vote, as desiganteddesignated on the reverse hereof, all the common stock, $.01 par value per share, of Iron Mountain Incorporated held of record by the undersigned or with respect to which the undersigned is entitled to vote or act at the Annual Meeting of Shareholders to be held on May 22, 200327, 2004 at 10:00 a.m., local time, or any adjournment or postponement thereof.

        This proxy when properly executed will be voted in the manner directed herein by the undersigned shareholder. If no direction is made, this proxy will be voted FOR all of the Directors listed in Proposal 1, FOR the approval of the Iron Mountain Incorporated 2003 Employee Stock Purchase Planamendment to the Company's Amended and Restated Articles of Incorporation described in Proposal 2 and FOR the approval of the amendment to the Iron Mountain Incorporated 2003 Senior Executive2002 Stock Incentive ProgramPlan described in Proposal 3.

PROXY
[LOGO OF IRON MOUNTAIN INCORPORATED]

April    17, 2003, 2004

Dear Shareholder:

        It is a pleasure to invite you to the Company's 20032004 Annual Meeting in Boston, Massachusetts on Thursday, May 22, 2003,27, 2004, at 10:00 a.m., local time, at the offices of Sullivan & Worcester LLP, One Post Office Square, 23rd21^st Floor, Boston, Massachusetts.

        The Annual Report to Shareholders, Notice of Meeting, proxy statement and form of proxy are included herein. The matters listed in the Notice of Meeting are described in detail in the proxy statement.

        The vote of every shareholder is important. Mailing your completed proxy will not prevent you from voting in person at the meeting if you wish to do so.

        Please sign, date and promptly mail your proxy. Your cooperation will be greatly appreciated.

        Your Board of Directors and management look forward to greeting those shareholders who are able to attend.

[PROXY]

QuickLinks

IRON MOUNTAIN INCORPORATED 2003 EMPLOYEE STOCK PURCHASE PLANAppendix A

IRON MOUNTAIN INCORPORATED 2003 SENIOR EXECUTIVE INCENTIVE PROGRAMAppendix B