The Common Stock is listed for trading on the New York Stock Exchange and, after the merger, Iron Mountain DE common stock will be traded on the New York Stock Exchange under the same symbol, "IRM", as theadditional shares of Common Stock are currently traded. Theby the Company could have an antitakeover effect by making it more difficult to obtain stockholder approval of various actions, such as a merger or removal of management. Additionally, the issuance of additional shares of Iron Mountain DE common stock will continue to be representedCommon Stock by the same CUSIP number that is currently used for the Common Stock. There will be no interruption in the trading of the Common Stock as a result of the merger.

        The Reincorporation includes the implementation of a new certificate of incorporation, in the form attached hereto as Appendix B (the "Delaware Charter") and bylaws, in the form attached hereto as Appendix C (the "Delaware Bylaws") for Iron Mountain DE to replace the current articles of incorporation and bylaws of Iron Mountain PA (the "Pennsylvania Charter" and "Pennsylvania Bylaws", respectively). As a Delaware corporation, Iron Mountain DE will be subject to the Delaware General Corporation Law (the "DGCL"). Iron Mountain PA is subject to the Business Corporation Law of Pennsylvania (the "PaBCL"). Differences between the Delaware Charter and Delaware Bylaws, on the one hand, and the Pennsylvania Charter and Pennsylvania Bylaws, on the other hand, must be viewed in the context of the differences between the DGCL and the PaBCL. Material differences are discussed below under "—Comparison of the Charters and Bylaws of Iron Mountain PA and Iron Mountain DE and Significant Differences Between the Corporation Laws of Delaware and Pennsylvania".

        If approved by the shareholders, it is anticipated that the Reincorporation will be completed as soon thereafter as is practicable. As described in the Merger Agreement, however, the Board may abandon the Reincorporation or amend the Merger Agreement, subject to any restrictions imposed by the DGCL or the PaBCL, either before or after shareholder approval has been obtained if, in the opinion of the Board, circumstances arise that make such action advisable. Any amendment that would adversely affect Iron Mountain PA shareholders or effect a material change from the Delaware Charter in the form attached hereto and described herein, however, would require further approval by the holders of a majority of the outstanding shares of the Common Stock. The Board does not currently intend to make any material amendments to the Merger Agreement, nor does it intend to amend the Delaware Charter or Delaware Bylaws, in the forms attached hereto and described herein, should the Reincorporation be approved by the Company's shareholders.

        As provided in the PaBCL, Iron Mountain PA shareholders will not be entitled to exercise dissenters' rights or to demand payment for their shares in connection with the merger or the Reincorporation. See "—Comparison of the Charters and the Bylaws of Iron Mountain PA and Iron Mountain DE and Significant Differences Between the Corporation Laws of Delaware and Pennsylvania—Dissenters' Rights of Appraisal" below.

The following discussion summarizes certain aspects of the Reincorporation. The summary is not intended to be complete and is qualified in its entirety by reference to the Merger Agreement, the Delaware Charter and the Delaware Bylaws, copies of which are attached to this Proxy Statement as Appendices A, B and C, respectively, the DGCL and the PaBCL.

Principal Reasons for the Reincorporation in Delaware

        For many years, Delaware has followed a policy of encouraging incorporation in that state. In furtherance of that policy, Delaware has adopted comprehensive, modern and flexible corporate laws which are periodically updated and revised to meet changing business needs. Many corporations have initially chosen Delaware for their domicile, or have chosen to reincorporate in Delaware in a manner similar to that proposed by the Company. The Board believes the Reincorporation to be in the best interest of the Company and its shareholders for several reasons including, but not limited to:

•

it is anticipated that Delaware's substantial and well-developed body of case law construing the DGCL will provide the Company with greater predictability in its operations and business dealings;

•

the higher degree of certainty afforded by Delaware's well-established principles of corporate governance should enhance the Company's ability to attract and retain qualified directors and officers and to ensure conduct that is in the best interest of the stockholders;



•

the Delaware courts have developed a reputation for considerable expertise and sophistication in dealing with complex corporate issues; and



•

the Delaware legislature is particularly sensitive to issues regarding corporate law and is especially responsive to developments in modern corporate law.

Comparison of the Charters and the Bylaws of Iron Mountain PA and Iron Mountain DE and Significant Differences Between the Corporation Laws of Delaware and Pennsylvania

        As a result of the Reincorporation, Iron Mountain PA shareholders will become stockholders of Iron Mountain DE and the rights of all such former Iron Mountain PA shareholders will thereafter be governed by the Delaware Charter, the Delaware Bylaws and the DGCL. The rights of the Iron Mountain PA shareholders are presently governed by the Pennsylvania Charter, the Pennsylvania Bylaws and the PaBCL.

        The following summary, which does not purport to be a complete statement of the differences among the rights of the Iron Mountain DE stockholders and the Iron Mountain PA shareholders, sets forth certain differences between the DGCL and the PaBCL, between the Delaware Charter and the Pennsylvania Charter, and between the Delaware Bylaws and the Pennsylvania Bylaws. This summary is qualified in its entirety by reference to the full text of each of the documents, the DGCL and the PaBCL. The Delaware Charter and Delaware Bylaws are attached as Appendices B and C, respectively. Shareholders of the Company may obtain copies of the Pennsylvania Charter and Pennsylvania Bylaws at no cost by writing or telephoning us at: 745 Atlantic Avenue, Boston, Massachusetts 02111 Attention: Investor Relations, (617) 535-4799.

Limitations on Director Liability

        The DGCL permits a corporation to include a provision in its certificate of incorporation eliminating or limiting the personal liability of a director or officer to a corporation or its stockholders for damages for certain breaches of the director's fiduciary duty. This provision may not eliminate or limit the liability of a director for:

•

breaches of the director's duty of loyalty to a corporation or its stockholders;



•

acts or omissions not in good faith or involving intentional misconduct or knowing violations of law;



•

the payment of unlawful dividends or unlawful stock repurchases or redemptions; or



•

transactions in which the director received an improper personal benefit.

        Under the PaBCL and the Pennsylvania Bylaws, directors are liable for monetary damages only where the director has breached or failed to perform his or her duties under the PaBCL and that breach or failure to perform constitutes self-dealing, willful misconduct or recklessness. This limitation on liability does not extend to liability under a criminal statute or for the payment of taxes.

        The Delaware Charter eliminates the liability of directors to the fullest extent permissible under Delaware law. The Reincorporation and associated measures result in a director being shielded from suits by Iron Mountain DE or its stockholders for monetary damages for negligence or gross negligence by the director in failing to satisfy the director's duty of care. Consequently, an action for monetary damages against a director predicated on a breach of the duty of care will be available only if Iron Mountain DE or its stockholders are able to establish that the director was disloyal in his conduct,

failed to act in good faith, engaged in intentional misconduct, knowingly violated the law, derived an improper personal benefit or approved an illegal dividend or stock repurchase. The effect of such measures may be to limit or eliminate a remedy which might otherwise be available to a stockholder of Iron Mountain DE who is dissatisfied with the Board's decisions. Although an aggrieved stockholder could sue to enjoin or rescind an action taken or proposed by the Board, such remedies may not be timely or adequate to prevent or redress injury in all cases. On the other hand, there may be circumstances in which the DGCL and the Delaware Charter permit the Company or the stockholders to act against a director where the director's conduct would not be actionable under the PaBCL, such as breaches of a director's duty of loyalty or failure to perform his or her duties, that does not constitute self-dealing, willful misconduct or recklessness.

Indemnification of Officers and Directors

        The DGCL permits indemnification of officers and directors against liability incurred in third-party actions if the indemnitee acted in good faith and he or she reasonably believed the acts were in, or at least not opposed to, the best interests of the Company. Delaware law states that the indemnification provided by statute shall not be deemed exclusive of any other rights under any bylaw, agreement, vote of stockholders or disinterested directors or otherwise. As a result, under Delaware law, a Delaware corporation is permitted to indemnify its directors and officers within the limits established by law and public policy pursuant to an express contract, bylaw provision, stockholder vote, vote of disinterested directors or otherwise, any or all of which provide broad indemnification rights.

        The provisions of the PaBCL regarding indemnification are substantially similar to those of the DGCL. Under the PaBCL, Iron Mountain PA is permitted to indemnify its officers and directors so long as the indemnified person acted in good faith and in a manner he or she reasonably believed to be in, or not opposed to, the Company's best interests and, with respect to any criminal proceeding, had no reasonable cause to believe his or her conduct was unlawful. Pennsylvania law states that the indemnification provided by statute shall not be deemed exclusive of any other rights under any bylaw, agreement, vote of shareholders or disinterested directors or otherwise. Under the Pennsylvania Bylaws no indemnification is provided in the case of willful misconduct or recklessness.

Statutory Anti-Takeover Measures

        Delaware law permits a corporation to adopt a number of measures designed to reduce a corporation's vulnerability to hostile takeover attempts. Although the Board has not adopted or proposed any of these permitted anti-takeover measures at this time, there can be no assurance that the Board will not adopt anti-takeover measures available under Delaware law in the future. The availability of such measures under Delaware law, whether or not implemented, may have the effect of discouraging a future takeover attempt which a substantial number, or even a majority, of Iron Mountain DE's stockholders may deem to be in their best interests or in which stockholders may receive a premium for their shares over then current market prices. As a result, stockholders who might desire to participate in such transactions may not have the opportunity to do so.

        In addition to permitted anti-takeover measures, for certain corporations, Section 203 of the DGCL ("Section 203") limits the ability of a potential acquirer to conduct a hostile takeover. Under Section 203, certain "business combinations" by Delaware corporations with "interested stockholders" are subject to a three-year moratorium unless (1) priordiluting existing stockholder earnings per share, book value per share and voting power. The amendment to the dateRestated Certificate, if approved, could strengthen the stockholder became an "interested stockholder",position of management and might make the boardremoval of directors approved either the business combination or the transaction which resulted in the stockholder becoming an interested stockholder, (2) upon becoming an interested stockholder, the stockholder then owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced (excluding certain shares), or (3) at or subsequent to the date the stockholder became an "interested stockholder", the "business combination" is approved by the board of directors and authorized at an annual or special meeting by at least 66²/3%

of the corporation's outstanding voting stock, excluding shares owned by the interested stockholder unless the corporation's board of directors or stockholders has given a level of approval, or unless the "interested stockholder" owns at least 5% of the stock of the corporation. For purposes of Section 203, the term "business combination" includes mergers, asset sales and other similar transactions, and an "interested stockholder" is a person who, together with affiliates and associates, owns (or within the prior three years, did own) 15% ormanagement more of the corporation's voting stock. In effect, Section 203 prohibits a Delaware corporation from engaging in a "business combination" with an "interested stockholder" for three years following the date that person becomes an interested stockholder. As with other anti-takeover provisions, it is anticipated that the provisions of Section 203 of the DGCL may encourage companies interested in acquiring Iron Mountain DE to negotiate in advance with the Board, since the stockholder approval requirementdifficult, even if removal would be avoided if a majority of the directors then in office approve either the business combination or the transaction which results in the stockholder becoming an interested stockholder. Section 203 also has the effect of limiting the ability of a potential acquirer to make a two-tiered bid for Iron Mountain DE in which all stockholders would not be treated equally.

        Section 203 only applies to Delaware corporations which have a class of voting stock that is (1) listed on a national securities exchange, (2) authorized for quotation on the Nasdaq Stock Market or (3) held of record by more than 2,000 stockholders. Because Iron Mountain DE common stock will be traded on the NYSE, Section 203 is applicable to Iron Mountain DE. A Delaware corporation may elect not to be governed by Section 203 by a provision in its original certificate of incorporation or an amendment thereto or to the bylaws, which amendment must be approved by a majority stockholder vote and may not be further amended by the board of directors. Section 203 will be applicable to Iron Mountain DE because the Delaware Charter does not contain an election to opt out of being governed by Section 203.

        The Board recognizes that hostile takeover attempts do not always have unfavorable consequences or effects and may frequently begenerally beneficial to the stockholders, providing allCompany’s stockholders. The authorization to issue the additional shares of Common Stock would provide management with an increased 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 stockholders with considerable value for their shares. The Board believes, however, thatproposed amendment to the potential disadvantagesRestated Certificate is not a part of unapprovedany present plan by the Company’s management to render the takeover attempts, such as disruption of the Company's business and the possibility of terms which may be less favorable to all of the stockholders than would be available in a board-approved transaction, are sufficiently great that prudent steps to reduce the likelihood of such takeover attempts and to enable the Board to fully consider a proposed takeover attempt and actively negotiate its terms are in the best interests of the Company and its stockholders.more difficult.

The PaBCL contains provisions applicableproposed amendment to publicly held Pennsylvania corporations that may be deemedthe Restated Certificate is not the result of management’s knowledge of any specific effort to have an anti-takeover effect. Subchapters 25 D, E, F, G, H, I and Jaccumulate the Company’s securities or to obtain control of the PaBCL containCompany by means of a variety of such measures, including restrictions on certain mergers and other business combinations and restrictions on the acquisition of shares which would entitle the acquiring personmerger, tender offer, proxy solicitation in opposition to cast a specified percentage of votes in an election of directors.management or otherwise.

        Subchapter 25D (relating to fundamental changes) provides generally that certain transactions involving "interested shareholders," including mergers, consolidations, share exchanges, asset sales, divisions, voluntary dissolutions and winding up and certain reclassifications affecting the voting or share interests, require anRequired Vote

The affirmative vote of the majority of the votes entitled to be cast, without counting the vote of the interested shareholder, unless the board of directors approves the transaction or another exception applies. An "interested shareholder" is defined to include any shareholder who is a party to the covered transaction or who is treated differently from other shareholders in connection with such a transaction and any person or group acting in concert with, or which controls, is controlled by, or under common control with, that shareholder.

        Subchapter 25E (relating to control transactions) provides generally that if any person or group acquires 20% or more of the voting power of a publicly traded corporation, notice must be given to the

other shareholders, who then may demand from such person or group the fair value of their shares, including a proportionate amount of any control premium.

        Subchapter 25F (relating to business combinations) restricts the ability of a person who becomes an "interested shareholder" to enter into certain "business combinations" with the corporation for a period of five years, unless one of certain exceptions apply. The term "business combination" is defined broadly to include various transactions including mergers, consolidations, asset sales and other similar transactions. An "interested shareholder" is defined generally as the beneficial owner of at least 20% of a corporation's voting stock.

        Subchapter 25G (relating to control-share acquisitions) provides that a person who acquires for the first time 20% or more, 33¹/3% or more, or 50% or more of a company's voting shares shall not have any voting rights unless the disinterested shareholders approve such voting rights. If this approval is not obtained, the corporation may force the shareholder to sell his or her shares to the corporation.

        Subchapter 25H (relating to disgorgement) applies in the event that (1) any person or group publicly discloses that such person or group may acquire control of the corporation through any means or (2) a person or group acquires, or publicly discloses an offer or intent to acquire, 20% or more of the voting power of the corporation. Any profits from sales of equity securities of the corporation by such person or group during a period of 18 months subsequent to obtaining the status of a controlling person revert to the corporation if the securities sold were acquired during such 18 month period or within 24 months prior thereto.

        Subchapters 25D through 25J contain a wide variety of exemptions, exclusions and safe harbors. Subchapters I and J (relating to severance compensation for terminated employees and labor contracts) apply to certain acquisitions of shares and business combinations. In such cases, terminated employees may be entitled to severance payments and labor contracts may be given protection against termination. A Pennsylvania corporation may opt out of any of these provisions. Only subchapters 25D and 25F are applicable to Iron Mountain PA; the Pennsylvania Charter provides that subchapters 25E, 25G and 25H shall not be applicable to Iron Mountain PA and subchapters 25I and 25J are nullified by opting out of subchapter 25G.

Factors a Board May Consider in Exercising its Fiduciary Duties

        Delaware law does not contain any statutory provision permitting the board of directors, committees of the board or individual directors, when discharging their duties, to consider, and it is therefore unclear under current Delaware law whether the board of directors, committees of the board or individual directors may consider, the interests of any constituencies other than the corporation or its stockholders.

        The PaBCL, on the other hand, provides that in discharging their duties, the board of directors, committees of the board and individual directors may, in considering what is in the best interests of the corporation, consider, to the extent they deem appropriate, all pertinent factors, including the following:

•

the effects of any action upon certain groups, including shareholders, employees, suppliers, customers and creditors of the corporation, and on communities in which the corporation has offices or other establishments;



•

the corporation's short-term and long-term interests, including benefits which may accrue to the corporation from its long-term plans and the possibility that these interests may be best served by the corporation's continued independence; and



•

the resources, intent and conduct (past, stated and potential) of any person seeking to acquire control of the corporation.

Dividend Rights

        Under the DGCL, directors may, subject to any restrictions in a corporation's certificate of incorporation, declare and pay dividends either (1) out of its surplus or (2) if no surplus exists, out of its net profits, for the current fiscal year and/or the preceding fiscal year. The directors of a Delaware corporation may not declare dividends out of net profits, however, if the capital of the corporation is less than the aggregate amount of capital represented by the issued and outstanding stock of all classes having a preference upon the distribution of assets. The rights of stockholders of a Delaware corporation to receive dividends are subject to the rights and preferences of holders of future series of preferred stock with preferential dividend rights, if any. Iron Mountain PA is authorized to issue up to 10 million shares of Preferred Stock, but no Preferred Stock is issued and outstanding. Iron Mountain DE will similarly be authorized to issue 10 million shares of Preferred Stock.

        Under the PaBCL, a corporation is prohibited from making a distribution to its shareholders if, after giving effect to the distribution (1) the corporation would be unable to pay its debts as they become due in the usual course of business, or (2) the corporation's total assets would be less than the sum of its total liabilities plus the amount that would be needed upon the dissolution of the corporation to satisfy the rights, if any, of shareholders having superior preferential rights to the shareholders receiving the distribution.

        Like the Pennsylvania Charter, the Delaware Charter contains no restrictions regarding dividends.

Stock Redemptions and Repurchases

        Under the DGCL, a corporation may not purchase or redeem its own shares when the capital of the corporation is impaired or when such purchase or redemption would cause an impairment of the capital of the corporation. A Delaware corporation may, however, purchase or redeem any of its preferred shares if such shares will then be retired and the capital of the corporation is reduced in accordance with the DGCL. The PaBCL permits a corporation to redeem any and all classes of its shares and treats such redemption or repurchase like a dividend by the corporation to or for the benefit of its shareholders, subject to the same limitations described above under the caption "—Dividend Rights".

Voting Rights

        Although the DGCL permits cumulative voting, the Delaware Charter does not provide for cumulative voting in the election of directors. Pursuant to the Delaware Charter and Delaware Bylaws, holders of Iron Mountain DE common stock are entitled to one vote per share on all matters voted on by stockholders.

        The PaBCL grants cumulative voting rights to shareholders but allows an exception if the charter so provides. In the case of Iron Mountain PA, the Pennsylvania Charter prohibits cumulative voting in the election of directors. Pursuant to the PaBCL, holders of the Common Stock are entitled to one vote per share on all matters voted on by shareholders.

Shareholder Meetings

        Under the DGCL, if there is a failure to hold the annual meeting or to take action by written consent to elect directors in lieu of an annual meeting for a period of 30 days after the designated date for the annual meeting, or if no date has been designated for a period of 13 months after the latest to occur of the organization of the corporation, its last annual meeting or the last action by written consent to elect directors in lieu of an annual meeting, the Court of Chancery may summarily order a meeting to be held upon the request of any stockholder or director. Under the DGCL, a special meeting of the stockholders may be called by a corporation's board of directors or any other person as

may be authorized by a corporation's certificate of incorporation or bylaws. Like the Pennsylvania Bylaws, the Delaware Bylaws provide that special meetings of the stockholders may be called only by the chairman of the board or by the board of directors of Iron Mountain DE.

        Under the PaBCL, if the annual meeting for the election of directors is not held within six months after the date designated for the annual meeting pursuant to the bylaws, any shareholder may call the meeting at any time thereafter. Pursuant to the PaBCL, special meetings of shareholders may be called by the board of directors or by any officer or by any other persons as provided in the bylaws. The PaBCL provides that the shareholders of a publicly traded corporation do not have a statutory right to call a special meeting. The Pennsylvania Bylaws do not provide an affirmative right to shareholders to call a special meeting.

Action by Shareholders Without a Meeting

        Although Delaware law permits stockholder action to be taken by written consent, the Delaware Charter specifically prohibits action by written consent of stockholders. Similarly, Pennsylvania law permits shareholder action by consent, but the Pennsylvania Bylaws prohibit action by either unanimous or partial consent of shareholders.

Shareholder Proposals, Nominations and Rights to Elect Directors

        The DGCL and the PaBCL do not include provisions restricting the manner in which nominations for directors may be made by stockholders or the manner in which business may be brought before a meeting.

        The Pennsylvania Bylaws provide that nominations of persons for election to the Board may be made only by the Board, a committee of the Board or by any shareholder who complies with the notice provisions in the Pennsylvania Bylaws. Notice must be given by a shareholder of a nomination, in writing:

•

in the case of an annual meeting called for a date within 30 days before or after the anniversary date of the last annual meeting of shareholders, not less than 60 days nor more than 90 days prior to such anniversary; or



•

in the case of an annual meeting called for a date not within 30 days before or after the anniversary date of the last annual meeting, or in the case of a special meeting of shareholders for the purpose of electing directors, not later than the later of (1) the 90th day before the meeting date or (2) the close of business on the 10th day following the day on which public disclosure of the date of the meeting was made.

        The Pennsylvania Bylaws similarly restrict the right of shareholders to bring business before a meeting of shareholders by requiring advance notice to the corporation of the general nature of the business the shareholder seeks to bring before the meeting.

        The Delaware Bylaws contains substantially similar provisions.

Charter Amendments

        Under the DGCL, an amendment or change to the certificate of incorporation generally requires the approval of the board of directors, followed by the approval of the holders of a majority of the shares entitled to vote, unless the certificate of incorporation increases the required vote. The Delaware Charter does not require a greater percentage vote.

        Under the PaBCL, an amendment to the articles of incorporation requires the approval of the board of directors followed by the affirmative vote of a majority of the votes actually cast by all shareholders entitled to vote thereon at a meeting at which a quorum is present and, if any class or

series of shares is entitled to vote thereon as a class, the affirmative vote of a majority of the votes cast in each such class vote. Under the PaBCL, the shareholders of a publicly traded corporation are not entitled by statute to propose an amendment to the articles of incorporation.

Amendments to Bylaws

        Under the DGCL, bylaws may be adopted, amended or repealed by a vote of a majority of the stockholders entitled to vote thereon. Delaware law also allows for a majority of the board of directors to make changes to the corporation's bylaws if the certificate of incorporation confers this power upon the directors. The Delaware Charter will grant this power to directors. The power vested in the stockholders is not, however, divested or limited because the board of directors also has such power.

        Under the PaBCL, bylaws may be adopted, amended and repealed by a vote of a majority of the votes actually cast by all shareholders entitled to vote thereon, and, if any shareholders are entitled to vote as a class, the affirmative vote of the majority of votes cast by such class. This authority may be expressly vested in the board of directors by the bylaws, subject to the power of the shareholders to change such action, unless the subject of the amendment is solely within the province of the shareholders. The Pennsylvania Bylaws provide that the Pennsylvania Bylaws may be amended or repealed by the vote of a majority of all directors, except for amendments that are solely within the province of the shareholders, in which case the affirmative vote of a majority of the votes cast by all shareholders entitled to vote is required to amend or repeal the bylaws.

Mergers and Fundamental Corporate Transactions

        Under the DGCL, fundamental corporate transactions, such as mergers, consolidations, sales of all or substantially all of a corporation's assets and dissolutions, require the approval of a majority of the board of directors and approval of the holders of a majority of the shares of a corporation's common stock. Although the DGCL permits a corporation to increase the minimum percentage vote required, the Delaware Charter and Delaware Bylaws do not require a greater vote.

        Under the PaBCL, fundamental corporate transactions, such as mergers, consolidations, the sale, lease, exchange or other disposition of all, or substantially all, of the property and assets of a corporation and dissolutions, require board approval and approval by a majority of the votes actually cast by the shareholders entitled to vote thereon, and, if shareholders are entitled to vote as a class, the affirmative vote of the majority of votes cast by such class. Although the PaBCL permits a corporation to increase the minimum percentage vote required, the Pennsylvania Charter and Pennsylvania Bylaws do not increase the vote.

Dissenters' Rights of Appraisal

        Under the DGCL, unless the certificate of incorporation of a corporation provides otherwise, there are no appraisal rights in connection with a merger or consolidation to holders of shares that are listed on a national securities exchange, quoted on a national market system or held of record by more than 2,000 stockholders unless the plan of merger or consolidation requires the stockholders to accept anything other than stock of the surviving corporation or stock of another corporation that is listed on a national securities exchange, quoted on a national market system or held of record by more than 2,000 stockholders, cash in lieu of fractional shares or any combination of the foregoing. In addition, the DGCL denies appraisal rights to the stockholders of the surviving corporation in a merger if that merger did not require for its approval the vote of the stockholders of the surviving corporation. The Delaware Charter does not provide for additional appraisal rights.

        The PaBCL generally does not provide for dissenters' rights to holders of shares that are listed on a national securities exchange or held beneficially or of record by more than 2,000 shareholders.

Federal Income Tax Consequences

        The Reincorporation will qualify for federal income tax purposes as a tax free reorganization under section 368(a) of the Code. As a condition to the closing of the Reincorporation, Iron Mountain DE will receive an opinion from Sullivan & Worcester LLP to the effect that, on the basis of the existing provisions of the Code, U.S. Treasury regulations issued thereunder, current administrative rules, pronouncements and court decisions, for federal income tax purposes upon completion of the Reincorporation:

        (1)   The Reincorporation will constitute a "reorganization" within the meaning of section 368(a)(1)(F) of the Code, and Iron Mountain PA and Iron Mountain DE will each be a "party to a reorganization" within the meaning of section 368(b) of the Code;

        (2)   No gain or loss will be recognized by Iron Mountain PA's shareholders upon the exchange (whether actual or constructive) of their shares of Iron Mountain PA for shares of Iron Mountain DE in the Reincorporation; and

        (3)   The aggregate tax basis of the shares of Iron Mountain DE received (whether actually or constructively) by each shareholder of Iron Mountain PA pursuant to the Reincorporation will be the same as the aggregate tax basis of the shares of Iron Mountain PA held by such shareholder immediately prior to the Reincorporation, and the holding period of the shares of Iron Mountain DE received (whether actively or constructively) by each shareholder of Iron Mountain PA will include the period during which the shares of Iron Mountain PA surrendered therefor were held by such shareholder (provided that the shares of Iron Mountain PA were held as a capital asset on the date of the Reincorporation).

        Opinions of counsel are not binding upon the Internal Revenue Service (the "IRS") or the courts. The Company has not requested a ruling from the IRS with respect to the federal income tax consequences of the Reincorporation under the Code. Shareholders of Iron Mountain PA should consult their tax advisors regarding the effect, if any, of the proposed Reincorporation in light of their individual circumstances. In particular, because the above discussion relates only to the U.S. federal income tax consequences of the Reincorporation, shareholders of Iron Mountain PA should also consult their tax advisors as to the foreign, state and local tax consequences, if any, of the Reincorporation.

Required Vote

        The affirmative vote of holders of a majority of the votes properly cast at the Annual Meeting on the proposal is required to approve the Merger Agreement andamendment to the Reincorporation, which will also constitute approval of the Delaware Charter and the Delaware Bylaws.Company’s Restated Certificate. For purposes of determining whether a majority of the votes have been cast in favor of the approval of the Merger Agreement andamendment to the Reincorporation,Company’s Restated Certificate, only those cast "For"“For” or "Against"“Against” are included, and any abstentions andor broker non-votes will not count in making that determination. Additionally, NYSE rules require that at least a majority of the votes that all stockholders are entitled to cast at the Annual Meeting must vote on the proposed amendment, whether for or against.

The Board recommends that you vote FOR the approvalproposal to amend the Company’s Restated Certificate to increase the number of the Merger Agreement and the Reincorporation.authorized shares of Common Stock from 200,000,000 to 400,000,000.

ITEM 3

APPROVAL OF AMENDMENT TO THE COMPANY'SIRON MOUNTAIN INCORPORATED
2003 EMPLOYEE2002 STOCK PURCHASEINCENTIVE PLAN

The Company’s Board has unanimously approved, and unanimously recommends that the shareholdersstockholders of the Company approve, an amendment, attached as Appendix A, to the 2003 Employee2002 Stock PurchaseIncentive Plan (the "ESPP"), attached hereto as Appendix D, to increase the number of shares of Common Stock authorized for issuance under the ESPP2002 Stock Incentive Plan from 1,125,0003,352,543 to 2,325,000.8,352,543.

The Board believes that equity-based compensation isequity interests are a significant factor in the Company'sCompany’s ability to attract, retain and motivate itskey employees, whodirectors and other service providers that are critical to the Company'sCompany’s long-term success and that an increase in the number of shares available for issuance under the ESPP2002 Stock Incentive Plan is necessary in order to provide those persons with incentives to serve the Company. In approving the increase in the number of shares reserved for issuance under the ESPP,2002 Stock Incentive Plan, the Board took into consideration theconsidered that only approximately 1,745,410 shares projected to beremained available for grant under the ESPP2002 Stock Incentive Plan as of April 1, 2006, the closeaverage annual rate of grants during 2002 through 2005 and the portion of the current offering on May 31, 2005. As of that date, it is projected that no more than 445,586Company’s outstanding shares will be available. Since at present no more than 195,000represented by equity compensation, including shares are available in any six-month offering period, sufficient shares remainsubject to complete only two additional offerings (ending November 30, 2005 and May 31, 2006 respectively). Under current offering period limitations, the increase in shares available by 1,200,000 is designed to ensure that a sufficient number of shares are available for an additional three years.options.

Summary of the ESPP2002 Stock Incentive Plan

The following summary of the material features of the ESPP2002 Stock Incentive Plan is qualified in its entirety by reference to the complete text of the ESPP, attached hereto2002 Stock Incentive Plan and the First Amendment thereto, which are filed as Appendix E.appendices to the Company’s Proxy Statements on Schedule 14A filed in April 2002 and in April 2004, respectively.

        Overview.The ESPP operates by granting,2002 Stock Incentive Plan permits the issuance of equity-based awards, including incentive stock options, nonqualified stock options, grants of Common Stock, whether or not subject to restrictions, and stock appreciation rights. The 2002 Stock Incentive Plan initially reserved 1,352,543 shares of Common Stock and the stockholders approved the First Amendment to the 2002 Stock Incentive Plan in a seriesMay 2004 to increase the number of offerings, optionsshares reserved to acquire3,352,543 shares of Common Stock. The Compensation Committee determinesIf stockholders approve the commencement date and duration of offerings. The Compensation Committee may also, and currently does, limitproposed amendment to the maximum2002 Stock Incentive Plan, the total amount of Common Stock available with respect to an offering.authorized for issuance under the 2002 Stock Incentive Plan will be 8,352,543.

        In general, offerings last for six monthsPurpose, Eligible Individuals, Effective Date and begin each JuneDuration.The 2002 Stock Incentive Plan became effective April 1, and December 1. During an offering, payroll deductions are accumulated on behalf of each participant. At the end2002. The purpose of the offering, the options are exercised2002 Stock Incentive Plan is to encourage employees, officers, directors and the accumulated payroll deductions are retained by the Company as full payment of the option price. Each participant receives a 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. The "option price" of shares of Common Stock will be 85% of the lower of the fair market value of Common Stock at the start of the offering or on the exercise date. Fair market value under the ESPP generally means the average of the highest and lowest sale price of Common Stock on the date in question. The Compensation Committee 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.

        Shares Available under the ESPP.    As of April 1, 2005, there were approximately 445,586 shares available for future sale under the ESPP. The proposed amendment to the ESPP will increase the total number of shares that may be subject to options under the ESPP by 1,200,000.

        If an option expires or is terminated or surrendered, the shares allocable to the option may again be available under the ESPP. If at the end of an offering there are not enough shares available to satisfy all desired purchases, a pro rata allocation of the available shares will be made among all participants, and any excess payroll deductions will be returned to participants.

        Eligibility and Participation.    In general, any employeeconsultants of the Company or a subsidiary that is (or is treatedand our subsidiaries who render services to us 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