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Exhibit 99.1

FOR IMMEDIATE RELEASE

Contact: Stephen P. Golden
Director of Investor Relations
(617) 535-4799

Iron Mountain Incorporated Reports Second Quarter 2003 Financial Results

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Total Revenues are $359 Million, Up 10%



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Net Income is $0.23 per Diluted Share



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Company Completes the Acquisition of Hays IMS

Boston, MA—July 31, 2003—Iron Mountain Incorporated (NYSE: IRM), the leader in records and information management services, today reported higher revenues, operating income, EBITDA and net income for the quarter ended June 30, 2003. The Company also reported that, as previously announced, it completed the acquisition of the information management services business of Hays plc ("Hays IMS") in Europe and Texas on July 16, 2003.

Iron Mountain's total consolidated revenues for the quarter ended June 30, 2003 grew to $359 million, an increase of 10% compared with the quarter ended June 30, 2002. For the quarter, storage revenues grew 12% and service revenues grew 7% compared to the prior year. Storage revenues, which are considered a key performance indicator for the records and information management services industry, are largely recurring since customers typically retain their records for many years. This marks the 58th consecutive quarter for which Iron Mountain has reported increased storage revenues.

For the second quarter of 2003, the storage and service revenue internal growth rates were 8.4% and 2.9%, respectively, yielding a total internal revenue growth rate of 6.1%. The storage internal growth rate continued its upward trend. Service revenue growth rates in the Company's North American business units were impacted in several ways. The North American paper business experienced lower levels of customer termination activity, archived records destructions and large special projects compared to prior periods. In addition, the Company's Off-Site Data Protection business continued to feel the pressure of tight information technology spending particularly with respect to its complementary services, most notably, data product sales. The Company believes that service revenues will likely grow at a slower rate than storage revenues for the balance of the year.

Richard Reese, the Company's Chairman and CEO, stated, "The Company reported solid results for the second quarter despite slower growth rates in certain service revenue lines. Storage internal growth rates continued to increase, margins were as expected and we generated free cash flow before acquisitions and investments on a year-to-date basis. We experienced slower growth rates in certain complementary service lines. Our international businesses are performing very well across the board and two weeks ago, we completed a very important acquisition in Europe, Hays IMS. This strategic acquisition doubles the size of our business in Europe and our initial observations reaffirm our enthusiasm for this transaction."

Operating income for the second quarter of 2003 was $69 million, or 19% of revenues, compared to $62 million, or 19% of revenues, for the same period in 2002. Net Income for the quarter was $20 million, or $0.23 per diluted share, compared to $20 million, or $0.23 per diluted share, for the same period in 2002. Included in net income for 2003 is $5 million of other income, net comprised of a $19 million foreign currency gain, due primarily to the strengthening of the Canadian dollar and the pound Sterling against the U.S. dollar, partially offset by a $14 million charge for the early extinguishment of debt related to the redemption of the Company's 8³/4% notes. The Company will record a pre-tax charge of $6 million in the third quarter ending September 30, 2003, for the early extinguishment of debt related to the redemption of $50 million aggregate principal amount of the

8¹/8% notes of its subsidiary Iron Mountain Canada Corporation. Included in net income for 2002 is $6 million of other income, net comprised almost entirely of a foreign currency gain.

        EBITDA (earnings from continuing operations before interest, taxes, depreciation and amortization) was $103 million, or 28.6% of revenues, for the quarter ended June 30, 2003 compared to $94 million, or 28.6% of revenues, for the quarter ended June 30, 2002.

        Iron Mountain believes that EBITDA is useful to investors because it is an important financial measure used in evaluating the Company's performance, as EBITDA is an internally generated source of funds for investment in continued growth and for servicing indebtedness. Holders of the Company's publicly issued debt use EBITDA and EBITDA-based calculations as important criteria for evaluating the Company and, as a result, all of its bond indentures and covenants include EBITDA and EBITDA-based calculations as primary measures of financial performance. However, EBITDA is subject to foreign currency fluctuations and, under new accounting rules, debt extinguishment charges. As a result, operating income, which is less affected by these items, is emerging as an important measure of the Company's financial performance. EBITDA is not a measurement of financial performance under accounting principles generally accepted in the United States, or GAAP, and should not be considered as a substitute for operating or net income (as determined in accordance with GAAP).

        Below is a reconciliation of Operating Income to EBITDA Before Extraordinary Item to Net Income:

		Quarter Ended June 30,						Six Months Ended June 30,
		2002			2003			2002			2003
Operating Income		$	62,346		$	68,651		$	119,530		$	140,878
	Add: Depreciation and Amortization		26,353			30,765			51,509			60,714
			88,699			99,416			171,039			201,592
	Less: Other Income, net		(6,268	)		(4,722	)		(4,956	)		(7,982	)
	Minority Interests in Earnings of Subsidiaries		1,098			1,558			2,055			2,858
EBITDA Before Extraordinary Item		$	93,869		$	102,580		$	173,940		$	206,716
	Less: Depreciation and Amortization		26,353			30,765			51,509			60,714
	Interest Expense, net		32,788			36,397			65,668			71,962
	Provision for Income Taxes		14,739			15,285			24,256			32,623
	Cumulative Effect of Change in Accounting Principle		—			—			6,396			—
Net Income		$	19,989		$	20,133		$	26,111		$	41,417
Major Components of Other (Income) Expense, net:
	Foreign Exchange Effects	$	(6,315	)	$	(18,551	)	$	(6,274	)	$	(23,634	)
	Debt Extinguishment Charges	$	—		$	13,841		$	1,222		$	15,665

For the six months ended June 30, 2003 Iron Mountain reported total consolidated revenues of $711 million, an increase of 10% with storage revenues growing at 11% and service revenues growing at 9% compared to the prior year. For the period, storage and service revenue internal growth rates were 8.3% and 5.1%, respectively, yielding a total internal revenue growth rate of 7.0%. Operating income for the first half of 2003 was $141 million, or 20% of revenues, compared to $120 million, or 19% of revenues, for the same period in 2002. Income from continuing operations before extraordinary items was $41 million, or $0.48 per diluted share, for the first six months of 2003, compared to $33 million, or $0.38 per diluted share, for the same period in 2002. Included in income from continuing operations before extraordinary items for the first half of 2003 is $8 million of other income, net comprised of a $24 million foreign currency gain, due primarily to the strengthening of the Canadian dollar and the pound Sterling against the U.S. dollar, partially offset by $16 million of

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charges for the early extinguishment of debt related to the Company's 2003 refinancing activities. Included in income from continuing operations before extraordinary items for the first half of 2002 is $5 million of other income, net for the first half of 2002 is comprised primarily of a $6 million foreign currency gain offset by $1 million of charges for the early extinguishment of debt related to the Company's 2002 refinancing activities.

Net Income for the first six months of 2003 was $41 million, or $0.48 per diluted share, compared to $26 million, or $0.30 per diluted share, for the same period in 2002. Included in net income for 2002 is a $6 million after tax charge representing the cumulative effect of a change in accounting principle recorded in the first quarter of 2002.

EBITDA before extraordinary item was $207 million, or 29.1% of revenues, for the six months ended June 30, 2003 compared to $174 million, or 27.0% of revenues, for the six months ended June 30, 2002.

Company Completes Successful Refinancings; Closes Hays IMS Acquisition

During the second quarter of 2003, the Company completed the redemption of its 8³/4% notes by retiring the $220 million of aggregate principal amount outstanding at March 31, 2003. In June 2003, the Company sold $150 million of 6⁵/8% notes at par. The net proceeds to the Company of $148 million were used to redeem $50 million in aggregate principal amount of the 8¹/8% notes, to fund a portion of the Hays IMS purchase price and for general corporate purposes.

In July 2003, Iron Mountain and its European joint venture, Iron Mountain Europe Ltd., completed the acquisition of Hays IMS. Total consideration for the transaction was 200 million pounds Sterling, including 14.5 million pounds Sterling for the US piece of the business. The Hays IMS acquisition adds 7 new markets in the UK, Germany, Norway and Belgium.

"This is a great transaction for Iron Mountain." said Richard Reese, "We have solidified our position as the leader in records and information management on three continents allowing us to better serve our new and existing customers. This transaction will create opportunities for our employees and continue to add value for our shareholders."

Financial Performance Outlook

The following statements are based on current expectations and do not include the potential impact of any future acquisitions. These statements are forward-looking, and actual results may differ materially. Please refer to the cautionary language included in this press release when considering this information. The Company undertakes no obligation to update this information. The Company is providing the following financial guidance for the quarter ending September 30, 2003 and the full year ending December 31, 2003, which includes the estimated impact of the Hays IMS acquisition (dollars in millions):

					Full Year Ending December 31, 2003
	Quarter Ending September 30, 2003
					Previous						Current
	Low		High		Low			High			Low			High
Revenues	$	375	$	385	$	1,440		$	1,480		$	1,480		$	1,510
Operating Income		69		74		270			290			273			293
Depreciation & Amortization		~33				127			123			133			127
Capital Expenditures						190			215			190			215
Internal Growth						9	%		11	%		6	%		8	%

Iron Mountain's conference call to discuss the second quarter 2003 financial results will be held today at 11:00 am eastern time. In order to further enhance the overall quality of its investor

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communications, the Company will simulcast the conference call on its website at www.ironmountain.com. A slide presentation providing summary financial and statistical information that will be discussed on the conference call will also be posted to the website and available for real-time viewing. The slide presentation and replays of the conference call will be available on the website for future reference.

About Iron Mountain

        Iron Mountain Incorporated is the world's trusted partner for outsourced records and information management services. Founded in 1951, the Company has grown to service more than 150,000 customer accounts throughout the United States, Canada, Europe and Latin America. Iron Mountain offers records management services for both physical and digital media, disaster recovery support services, and consulting—services that help businesses save money and manage risks associated with legal and regulatory compliance, protection of vital information, and business continuity challenges. For more information, visit www.ironmountain.com.

Certain Important Factors

This press release contains certain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, and is subject to the safe-harbor created by such Act. Forward-looking statements include our third quarter and full year 2003 financial performance outlook and statements regarding our goals, beliefs, strategies, objectives, plans or current expectations. These statements involve known and unknown risks, uncertainties and other factors that may cause the actual results to be materially different from those contemplated in the forward-looking statements. Such factors include, but are not limited to: (i) changes in customer preferences and demand for the Company's services; (ii) changes in the price for the Company's services relative to the cost of providing such services; (iii) the cost and availability of financing for contemplated growth; (iv) the Company's ability or inability to complete acquisitions on satisfactory terms and to integrate acquired companies efficiently; (v) in the various digital businesses on which the Company is embarking, capital and technical requirements will be beyond the Company's means, markets for the Company's services will be less robust than anticipated, or competition will be more intense than anticipated; (vi) the possibility that business partners upon which the Company depends for technical assistance or management and acquisition expertise outside the United States will not perform as anticipated; (vii) changes in the political and economic environments in the countries in which the Company's international subsidiaries operate; and (viii) other trends in competitive or economic conditions affecting Iron Mountain's financial condition or results of operations not presently contemplated. Iron Mountain undertakes no obligation to release publicly the result of any revision to these forward-looking statements that may be made to reflect events or circumstances after the date hereof or to reflect the occurrence of unanticipated events.

        NOTE:    Condensed Consolidated Financial Statements of Iron Mountain Incorporated follow.

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Iron Mountain Incorporated
Condensed Consolidated Statements of Operations
(Amounts in Thousands except Per Share Data)
(Unaudited)

				Three Months Ended June 30,						Six Months Ended June 30,
				2002			2003			2002			2003
Revenues:
	Storage			$	186,984		$	208,969		$	370,420		$	411,800
	Service and Storage Material Sales				140,736			150,301			274,498			299,281
			Total Revenues		327,720			359,270			644,918			711,081
Operating Expenses:
	Cost of Sales (Excluding Depreciation)				155,407			162,032			307,853			322,183
	Selling, General and Administrative				85,312			96,134			167,506			187,290
	Depreciation and Amortization				26,353			30,765			51,509			60,714
	Merger-Related Expenses				280			—			580			—
	(Gain) Loss on Disposal / Writedown of Property, Plant and Equipment, Net				(1,978	)		1,688			(2,060	)		16
			Total Operating Expenses		265,374			290,619			525,388			570,203
Operating Income					62,346			68,651			119,530			140,878
Interest Expense, Net					32,788			36,397			65,668			71,962
Other income, Net					(6,268	)		(4,722	)		(4,956	)		(7,982	)
		Income from Continuing Operations Before Provision for Income Taxes and Minority Interest			35,826			36,976			58,818			76,898
Provision for Income Taxes					14,739			15,285			24,256			32,623
Minority Interest in Earnings of Subsidiaries					1,098			1,558			2,055			2,858
		Income from Continuing Operations Before Cumulative Effect of Change in Accounting Principle			19,989			20,133			32,507			41,417
Cumulative Effect of Change in Accounting Principle (Net of Minority Interest) (1)					—			—			(6,396	)		—
			Net Income	$	19,989		$	20,133		$	26,111		$	41,417
Income From Continuing Operations Before Cumulative Effect of Change in Accounting Principle Per Share — Basic				$	0.24		$	0.24		$	0.38		$	0.49
Income From Continuing Operations Before Cumulative Effect of Change in Accounting Principle Per Share — Diluted				$	0.23		$	0.23		$	0.38		$	0.48
Net Income Per Share—Basic				$	0.24		$	0.24		$	0.31		$	0.49
Net Income Per Share—Diluted				$	0.23		$	0.23		$	0.30		$	0.48
Weighted Average Common Shares Outstanding—Basic					84,534			85,234			84,454			85,166
Weighted Average Common Shares Outstanding—Diluted					86,078			86,793			86,024			86,672
EBITDA Before Extraordinary Item				$	93,869		$	102,580		$	173,940		$	206,716

(1)

Represents the non-cash charge related to the impairment of goodwill associated with the Company's investment in South America due primarily to the deterioration of the economy and the devaluation of the currency in Argentina.

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Iron Mountain Incorporated
Condensed Consolidated Balance Sheets
(Amounts in Thousands)
(Unaudited)

			December 31, 2002			June 30, 2003
ASSETS
Current Assets:
	Cash and Cash Equivalents		$	56,292		$	177,863
	Accounts Receivable (less allowances of $20,274 and $20,353, respectively)			225,416			239,987
	Other Current Assets			85,332			68,879
		Total Current Assets		367,040			486,729
Property, Plant and Equipment:
	Property, Plant and Equipment at Cost			1,577,588			1,701,035
	Less: Accumulated Depreciation			(338,400	)		(394,041	)
		Property, Plant and Equipment, net		1,239,188			1,306,994
Other Assets:
	Goodwill, net			1,544,974			1,587,402
	Other Non-current Assets, net			79,453			95,090
		Total Other Assets		1,624,427			1,682,492
		Total Assets	$	3,230,655		$	3,476,215
LIABILITIES AND SHAREHOLDERS' EQUITY
Current Liabilities:
	Current Portion of Long-term Debt		$	69,732		$	52,895
	Other Current Liabilities			358,230			370,131
		Total Current Liabilities		427,962			423,026
Long-term Debt, Net of Current Portion				1,662,365			1,822,375
Other Long-term Liabilities				133,335			160,798
Minority Interests				62,132			68,460
Shareholders' Equity				944,861			1,001,556
		Total Liabilities and Shareholders' Equity	$	3,230,655		$	3,476,215

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QuickLinks

Iron Mountain Incorporated Reports Second Quarter 2003 Financial Results
Company Completes Successful Refinancings; Closes Hays IMS Acquisition
Financial Performance Outlook
Certain Important Factors
Iron Mountain Incorporated Condensed Consolidated Statements of Operations (Amounts in Thousands except Per Share Data) (Unaudited)
Iron Mountain Incorporated Condensed Consolidated Balance Sheets (Amounts in Thousands) (Unaudited)
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