<SUBMISSION>
<ACCESSION-NUMBER>0001047469-04-000293
<TYPE>8-K
<PUBLIC-DOCUMENT-COUNT>2
<PERIOD>20040107
<ITEMS>5
<ITEMS>7
<FILING-DATE>20040107
<FILER>
<COMPANY-DATA>
<CONFORMED-NAME>IRON MOUNTAIN INC/PA
<CIK>0001020569
<ASSIGNED-SIC>4220
<IRS-NUMBER>232588479
<STATE-OF-INCORPORATION>PA
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<FILING-VALUES>
<FORM-TYPE>8-K
<ACT>34
<FILE-NUMBER>001-13045
<FILM-NUMBER>04512398
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>745 ATLANTIC AVENUE
<CITY>BOSTON
<STATE>MA
<ZIP>02111
<PHONE>6175354766
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>745 ATLANTIC AVENUE
<CITY>BOSTON
<STATE>MA
<ZIP>02111
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>PIERCE LEAHY CORP
<DATE-CHANGED>19960807
</FORMER-COMPANY>
</FILER>
<DOCUMENT>
<TYPE>8-K
<SEQUENCE>1
<FILENAME>a2126023z8-k.htm
<DESCRIPTION>FORM 8-K
<TEXT>
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<P ALIGN="CENTER"><FONT SIZE=5><B>SECURITIES AND EXCHANGE COMMISSION<BR>  </B></FONT><FONT SIZE=2><B>WASHINGTON, D.C. 20549  </B></FONT></P>

<BR>
<P ALIGN="CENTER"><FONT SIZE=5><B>FORM 8-K  </B></FONT></P>

<P ALIGN="CENTER"><FONT SIZE=3><B>CURRENT REPORT  </B></FONT></P>

<P ALIGN="CENTER"><FONT SIZE=3><B> Pursuant to Section&nbsp;13 of 15(d) of The Securities Exchange Act of 1934  </B></FONT></P>

<P ALIGN="CENTER"><FONT SIZE=2>Date of Report (Date of earliest event reported): </FONT><FONT SIZE=2><B>January&nbsp;7, 2004</B></FONT></P>

<P ALIGN="CENTER"><FONT SIZE=5><B>IRON MOUNTAIN INCORPORATED<BR>  </B></FONT><FONT SIZE=2>(Exact name of registrant as specified in its charter) </FONT></P>

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<TD WIDTH="32%" ALIGN="CENTER"><FONT SIZE=2><B>PENNSYLVANIA<BR> </B></FONT><FONT SIZE=2>(State or other jurisdiction<BR>
of incorporation)</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="32%" ALIGN="CENTER"><FONT SIZE=2><B>1-13045<BR> </B></FONT><FONT SIZE=2>(Commission<BR>
File Number)</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="32%" ALIGN="CENTER"><FONT SIZE=2><B>23-2588479<BR> </B></FONT><FONT SIZE=2>(IRS Employer<BR>
Identification No.)</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD COLSPAN=5 ALIGN="CENTER"><FONT SIZE=2><BR>
<BR></FONT> <FONT SIZE=2><B>745 Atlantic Avenue<BR>
Boston, Massachusetts 02111<BR> </B></FONT><FONT SIZE=2>(Address of principal executive offices, including zip code)</FONT></TD>
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<P ALIGN="CENTER"><FONT SIZE=2><B>(617)&nbsp;535-4766<BR>  </B></FONT><FONT SIZE=2>(Registrant's telephone number, including area code) </FONT></P>

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<P><FONT SIZE=2><A
NAME="ca1012_item_5._other_events_and_regulation_fd_disclosure"> </A>
<A NAME="toc_ca1012_1"> </A>
<BR></FONT><FONT SIZE=2><B>Item 5.&nbsp;&nbsp;&nbsp;&nbsp;Other Events and Regulation FD Disclosure    <BR>    </B></FONT></P>


<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;On January&nbsp;7, 2004, we announced a proposed offering of &pound;125&nbsp;million in aggregate principal amount of Senior Subordinated Notes due
2014. We intend to use the net proceeds from the offering to fund our offer to acquire Mentmore plc's 49.9% equity interest in Iron Mountain Europe Limited at a purchase price of
&pound;82.5&nbsp;million, including the repayment of trade and working capital funding Iron Mountain Europe owes to Mentmore plc (the "Acquisition"), as previously disclosed in our Current
Report on Form&nbsp;8-K dated December&nbsp;10, 2003, and for general corporate purposes, including the possible repayment of outstanding borrowings under our revolving credit
facility, the possible repayment of other indebtedness and possible future acquisitions and investments (such offering, including the intended use of net proceeds, is hereinafter referred to as the
"January&nbsp;2004 Debt Offering"). Iron Mountain Europe expects to report revenues of approximately &pound;110&nbsp;million for its fiscal year ended October&nbsp;31, 2003 (which is
expected to include approximately &pound;28&nbsp;million of revenues from the European records management operations of Hays plc for the four months after its acquisition by Iron Mountain
Europe). Iron Mountain Europe has experienced a compound annual revenue growth rate in excess of 40% for the past five years. A copy of our press release regarding the January&nbsp;2004 Debt
Offering is being filed as exhibit&nbsp;99.1 to this report. </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
notes are being sold only to qualified institutional buyers under Rule&nbsp;144A and to persons outside the United States under Regulation&nbsp;S of the Securities Act of 1933.
The notes have not been and will not be registered under the Securities Act of 1933 or under the securities laws of any jurisdiction, and, unless so registered under the Securities Act of 1933, may
not be offered or sold in the United States except pursuant to an exemption from, or in a transaction not subject to, the registration requirements of the Securities Act of 1933 and applicable state
securities laws or the securities laws of other jurisdictions. This Form&nbsp;8-K does not constitute an offer, offer to sell, or solicitation of an offer to buy any securities in any
jurisdiction in which such offering, solicitation or sale would be unlawful. </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
December&nbsp;2003, we completed an underwritten public offering of $170&nbsp;million in aggregate principal amount of our 6<SUP>5</SUP>/<SMALL>8</SMALL>% Senior Subordinated Notes due 2016
at a price to investors of 96.5% of par, plus accrued interest from June&nbsp;20, 2003. Our net proceeds of $161.3&nbsp;million, after paying underwriters' discounts and commissions and
transaction fees, were used to redeem $65&nbsp;million in aggregate principal amount of the outstanding 8<SUP>1</SUP>/<SMALL>8</SMALL>% Senior Notes due 2008 of Iron Mountain Canada Corporation, our wholly
owned subsidiary, at a purchase price equal to $1,043.13 per $1,000 principal amount of 8<SUP>1</SUP>/<SMALL>8</SMALL>% Senior Notes, plus accrued and unpaid interest to the date of purchase, and the remainder
was used to repay borrowings under our revolving credit facility (such offering and the related use of net proceeds are hereinafter referred to as the "December&nbsp;2003 Debt Issuance"). We will
record a charge to other (income) expense, net of $7.2&nbsp;million ($4.6 million, net of tax) in the fourth quarter of 2003 related to
the early retirement of the 8<SUP>1</SUP>/<SMALL>8</SMALL>% Senior Notes, which consists of redemption premiums and transaction costs, as well as unamortized original issue discount related to these notes. </FONT></P>

<P><FONT SIZE=2><B>(b)&nbsp;&nbsp;&nbsp;&nbsp;Pro Forma Financial Information  </B></FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In this Form&nbsp;8-K we are providing pro forma information for the nine months ended September&nbsp;30, 2003 and the year ended
December&nbsp;31, 2002 previously filed in our Form&nbsp;10-Q for the quarter ended September&nbsp;30, 2003 and our Annual Report on Form&nbsp;10-K, as amended by
Amendment Number 1 on Form&nbsp;10-K/A, for the year ended December&nbsp;31, 2002. </FONT></P>


<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Assuming
we completed (a) the January&nbsp;2004 Debt Offering at an offering price of 100% of the principal amount of the notes and an interest rate of 7.5% and (b) the December 2003
Debt Issuance (collectively, the "Pro Forma Transactions") in each case as of January&nbsp;1, 2002, interest expense would have increased and minority interest in earnings of subsidiaries and net
income would have decreased </FONT></P>

<P ALIGN="CENTER"><FONT SIZE=2>2</FONT></P>

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<P><FONT SIZE=2>by
$12.1&nbsp;million, $3.5&nbsp;million and $4.2&nbsp;million, respectively, for the nine months ended September&nbsp;30, 2003 and $16.0&nbsp;million, $3.2&nbsp;million and
$6.9&nbsp;million, respectively, for the year ended December&nbsp;31, 2002. </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Assuming
the Pro Forma Transactions had occurred as of September 30, 2003, significant adjustments to our consolidated balance sheet as of September&nbsp;30, 2003 would include a
decrease in other current liabilities of $36.9&nbsp;million (relating to trade and working capital funding owed to Mentmore and repaid in connection with the Acquisition), a net increase in
long-term debt of $153.9&nbsp;million, a decrease in minority interests of $62.4&nbsp;million and a net decrease in shareholders' equity of $4.6&nbsp;million (relating to the debt
extinguishment charge). </FONT></P>

<P><FONT SIZE=2><I>Key Bond Leverage Ratio  </I></FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operation&#151;Liquidity and Capital Resources of our previously
filed Form&nbsp;10-Q for the nine months ended September&nbsp;30, 2003 we disclosed that our key bond leverage ratio, as calculated per our bond indentures, was 5.1x as of
September&nbsp;30, 2003. Our key bond leverage ratio, recalculated on a pro forma basis assuming the Pro Forma Transactions had been completed as of January&nbsp;1, 2002, would increase to 5.5x as
of September&nbsp;30, 2003. We are considering designating Iron Mountain Europe Limited and certain of its subsidiaries as excluded restricted subsidiaries, as defined in our bond indentures, though
there can be no assurance that we will do so or
as to the timing of any such designation. If we were to do so, the pro forma bond leverage ratio would be 5.1x. </FONT></P>

<P><FONT SIZE=2><A
NAME="ca1012_item_7._financial_statements_and_exhibits"> </A>
<A NAME="toc_ca1012_2"> </A>
<BR></FONT><FONT SIZE=2><B>Item 7.&nbsp;&nbsp;&nbsp;&nbsp;Financial Statements and Exhibits    <BR>    </B></FONT></P>

<UL>
<DL compact>
<DT style='margin-bottom:-11pt;'><FONT SIZE=2>(c)</FONT></DT><DD><FONT SIZE=2>Exhibits.
</FONT></DD></DL>
</UL>
<BR>

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<TH WIDTH="11%" ALIGN="LEFT"><FONT SIZE=1><B>EXHIBIT NO.<BR> </B></FONT><HR NOSHADE></TH>
<TH WIDTH="3%"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH WIDTH="86%" ALIGN="LEFT"><FONT SIZE=1><B>ITEM<BR> </B></FONT><HR NOSHADE></TH>
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<TR VALIGN="TOP">
<TD WIDTH="11%" ALIGN="RIGHT"><FONT SIZE=2>99.1</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="86%"><FONT SIZE=2>Press release dated January 7, 2004.</FONT></TD>
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<P ALIGN="CENTER"><FONT SIZE=2>3</FONT></P>

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<P ALIGN="CENTER"><FONT SIZE=2><A
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<A NAME="toc_jc1012_1"> </A>
<BR></FONT><FONT SIZE=2><B>SIGNATURES    <BR>    </B></FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned
thereunto duly authorized. </FONT></P>

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<TD WIDTH="47%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD COLSPAN=2><FONT SIZE=2>IRON MOUNTAIN INCORPORATED<BR>
(Registrant)</FONT></TD>
</TR>
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<TD WIDTH="47%"><FONT SIZE=2><BR>
&nbsp;</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD WIDTH="4%"><FONT SIZE=2><BR>
By:</FONT></TD>
<TD WIDTH="46%"><FONT SIZE=2><BR>
/s/&nbsp;&nbsp;</FONT><FONT SIZE=2>JEAN A. BUA</FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT><HR NOSHADE><FONT SIZE=2> Name: Jean A. Bua<BR>
Title: Vice President and Corporate Controller<BR></FONT>
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<P><FONT SIZE=2>Date:
January&nbsp;7, 2004 </FONT></P>

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<BR>
<P><br><A NAME="04BOS1012_1">QuickLinks</A><br></P><!-- TOC_BEGIN -->
<UL>
<FONT SIZE=2><A HREF="#toc_ca1012_1">Item 5. Other Events and Regulation FD Disclosure</A></FONT><BR>
<FONT SIZE=2><A HREF="#toc_ca1012_2">Item 7. Financial Statements and Exhibits</A></FONT><BR>
</UL>
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<FONT SIZE=2><A HREF="#toc_jc1012_1">SIGNATURES</A></FONT><BR>
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<TYPE>EX-99.1
<SEQUENCE>3
<FILENAME>a2126023zex-99_1.htm
<DESCRIPTION>EXHIBIT 99.1
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<P ALIGN="RIGHT"><FONT SIZE=2><A
NAME="ke1012_exhibit_99.1"> </A>
<A NAME="toc_ke1012_1"> </A>
<BR></FONT><FONT SIZE=2><B>Exhibit 99.1    <BR>    </B></FONT></P>

<P><FONT SIZE=2><B>FOR IMMEDIATE RELEASE:  </B></FONT></P>

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<TD WIDTH="13%"><FONT SIZE=2>Contact:</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="84%"><FONT SIZE=2>Stephen P. Golden<BR>
Director of Investor Relations<BR>
(617)&nbsp;535-4799</FONT></TD>
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<P ALIGN="CENTER"><FONT SIZE=2><A
NAME="ke1012_iron_mountain_incorporated_ann__iro03818"> </A>
<A NAME="toc_ke1012_2"> </A>
<BR></FONT><FONT SIZE=2><B>Iron Mountain Incorporated Announces Proposed GBP 125 Million<BR>  Senior Subordinated Notes Offering    <BR>    </B></FONT></P>

<P><FONT SIZE=2><B>Boston, MA</B></FONT><FONT SIZE=2>&#151;January&nbsp;7, 2004&#151;Iron Mountain Incorporated (NYSE: IRM), the leader in records and information management
services, announced today a proposed offering of GBP 125&nbsp;million in aggregate principal amount of its Senior Subordinated Notes due 2014. The Company intends to use the net proceeds from the
offering to fund the previously announced acquisition of Mentmore plc's 49.9% equity interest in Iron Mountain Europe Limited for total consideration of GBP 82.5&nbsp;million, which includes the
related repayment of trade and working capital funding owed to Mentmore by Iron Mountain Europe, and for general corporate purposes, including the possible repayment of outstanding borrowings under
its revolving credit facility, the possible
repayment of other indebtedness and possible future acquisitions and investments. The exact terms and timing of the offering will depend upon market conditions and other factors. </FONT></P>

<P><FONT SIZE=2>The
notes are being sold only to qualified institutional buyers under Rule&nbsp;144A and to persons outside the United States under Regulation&nbsp;S. The notes have not been registered under the
Securities Act of 1933 or under the securities laws of any other jurisdiction, and, unless so registered under the Securities Act of 1933, may not be offered or sold in the United States except
pursuant to an exemption from, or in a transaction not subject to, the registration requirements of the Securities Act and applicable state securities laws. This press release does not constitute an
offer, offer to sell, or solicitation of an offer to buy any securities in any jurisdiction in which such offering, solicitation or sale would be unlawful. </FONT></P>


<P><FONT SIZE=2>Stabilisation/FSA </FONT></P>

<P><FONT SIZE=2><B>About Iron Mountain  </B></FONT></P>

<P><FONT SIZE=2>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&#151;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 </FONT><FONT SIZE=2><I>www.ironmountain.com.</I></FONT></P>

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<BR>
<P><br><A NAME="04BOS1012_2">QuickLinks</A><br></P><!-- TOC_BEGIN -->
<UL>
<FONT SIZE=2><A HREF="#toc_ke1012_1">Exhibit 99.1</A></FONT><BR>
</UL>
<FONT SIZE=2><A HREF="#toc_ke1012_2">Iron Mountain Incorporated Announces Proposed GBP 125 Million Senior Subordinated Notes Offering</A></FONT><BR>

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