As filed with the Securities and Exchange Commission on May 1, 2000
                                                      Registration No. 333-24803



                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                             -----------------------

                         POST-EFFECTIVE AMENDMENT NO. 1

                                       to

                                    FORM S-8


             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
                             -----------------------

                         IRON MOUNTAIN INCORPORATED (1)

             (Exact name of registrant as specified in its charter)
                             -----------------------

           Delaware                                        04-3107342
(State or other jurisdiction                            (I.R.S. Employer
of incorporation or organization)                     Identification Number)

                               745 Atlantic Avenue
                           Boston, Massachusetts 02111
                                 (617) 535-4766
    (Address, including zip code, and telephone number, including area code,
                  of registrant's principal executive offices)
                              --------------------

              Iron Mountain Incorporated 1995 Stock Incentive Plan
                            (Full title of the plan)

                              ---------------------
                                C. Richard Reese
                       Chairman of the Board of Directors
                           and Chief Executive Officer
                           Iron Mountain Incorporated
                               745 Atlantic Avenue
                           Boston, Massachusetts 02111
                                 (617) 535-4766
   (Name, address, including zip code, telephone number, including area code,
                             of agent for service)
                              ---------------------
                                    Copy to:
                           Susan Forest Barrett, Esq.
                            Sullivan & Worcester LLP
                             One Post Office Square
                           Boston, Massachusetts 02109
                                 (617) 338-2800
                              ---------------------

- -------------------
(1) On February 1, 2000,  Iron  Mountain  Incorporated,  a Delaware  corporation
("Old Iron  Mountain"),  merged with and into Pierce Leahy Corp., a Pennsylvania
corporation  ("Pierce Leahy").  Pierce Leahy survived the merger and immediately
changed its name to "Iron Mountain  Incorporated,"  a  Pennsylvania  corporation
("New Iron Mountain"). This Post-Effective Amendment No. 1 is being filed by New
Iron Mountain on behalf of Old Iron Mountain.




                         Deregistration of Common Stock

     On April 9, 1997, Old Iron Mountain filed a Registration  Statement on Form
S-8  (Registration  No.  333-24803)  for the sale of an  aggregate  of 1,417,354
shares (as adjusted for a 3 for 2 stock split in July 1998) of common stock, par
value $.01 per  share,  of Old Iron  Mountain  ("Common  Stock")  under the Iron
Mountain  Incorporated  1995 Stock  Incentive Plan (the "Plan").  On February 1,
2000, Old Iron Mountain merged with and into Pierce Leahy, and New Iron Mountain
assumed the  obligations  of Old Iron Mountain  under the Plan.  Pursuant to Old
Iron Mountain's undertaking in the Registration  Statement,  this Post-Effective
Amendment  No. 1 is  being  filed by New Iron  Mountain  on  behalf  of Old Iron
Mountain to  deregister  all shares of Common Stock  registered  pursuant to the
Registration  Statement but remaining unsold as of the date this  Post-Effective
Amendment No. 1 is filed.








                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, as amended, the
registrant certifies that it has reasonable grounds to believe that it meets all
of  the   requirements  for  filing  on  Form  S-8  and  has  duly  caused  this
Post-Effective Amendment No. 1 to the Registration Statement to be signed on its
behalf by the  undersigned,  thereunto duly  authorized,  in the City of Boston,
Commonwealth of Massachusetts, on May 1, 2000.

                                   IRON MOUNTAIN INCORPORATED


                                   By:  /s/ C. Richard Reese
                                        C. Richard Reese
                                        Chairman and Chief Executive Officer

     Pursuant to the  requirements  of the  Securities  Act of 1933, as amended,
this  Post-Effective  Amendment  No. 1 to the  Registration  Statement  has been
signed  below  by the  following  persons  in the  capacities  and on the  dates
indicated.



       Signature                                    Title                                           Date

                                                                                         

 /s/ C. Richard Reese                    Chairman, Chief Executive                               May 1, 2000
C. Richard Reese                         Officer and Director

                                         President and Director
J. Peter Pierce

 /s/ John F. Kenny, Jr.                  Executive Vice President, Chief                         May 1, 2000
John F. Kenny, Jr.                       Financial Officer and Director

  *                                      Vice President and Corporate                            May 1, 2000
Jean A. Bua                              Controller (principal accounting
                                         officer)

                                         Director
Clarke H. Bailey

  *                                      Director                                                May 1, 2000
Constantin R. Boden








                                         Director
Kent P. Dauten

  *                                      Director                                                May 1, 2000
Eugene B. Doggett

                                         Director                                                May 1, 2000
B. Thomas Golisano

  *                                      Director                                                May 1, 2000
Arthur D. Little

                                         Director
Howard D. Ross

  *                                      Director                                                May 1, 2000
Vincent J. Ryan


*By:  /s/ C. Richard Reese
     C. Richard Reese
     Attorney-in-Fact pursuant to Power
     of Attorney previously filed as a
     part of this Registration Statement