PROSPECTUS SUPPLEMENT NO. 1 OFFER TO EXCHANGE all outstanding 8 3/4% SENIOR SUBORDINATED NOTES DUE 2009 ($250,000,000 principal amount outstanding) for 8 3/4% SENIOR SUBORDINATED NOTES DUE 2009 OF IRON MOUNTAIN INCORPORATED The Exchange Offer will expire at 5:00 p.m., New York City time on January 13, 1998, unless extended This Prospectus Supplement No. 1 is to notify holders of 8 3/4% Senior Subordinated Notes Due 2009 that in the Prospectus dated December 11, 1997 and the accompanying Letter of Transmittal and Notice of Guaranteed Delivery, all references to "8 3/4% Senior Notes Due 2009" should read "8 3/4% Senior Subordinated Notes Due 2009." Prospectus Supplement No. 1, dated December 22, 1997, to the Prospectus dated December 11, 1997.