
<PAGE>


                                                                      EXHIBIT 21

<TABLE>
<CAPTION>

----------------------------------------------------------------------------------------------------------------------
                                                     JURISDICTION OF                 NAMES UNDER WHICH
                                                     INCORPORATION OR                 THE ENTITY DOES
                    ENTITY NAME                       ORGANIZATION                        BUSINESS
----------------------------------------------------------------------------------------------------------------------
<S>                                                <C>                            <C>

Iron Mountain Records Management, Inc.               Delaware                        Iron Mountain Records Management
----------------------------------------------------------------------------------------------------------------------
Iron Mountain / National Underground, LLC            Delaware                        Iron Mountain National
                                                                                     Underground
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Consulting Services, LLC               Delaware                        Iron Mountain Consulting
                                                                                     Services
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Records Management of                  Delaware                        Iron Mountain Records Management
Michigan, Inc.
----------------------------------------------------------------------------------------------------------------------
Iron Mountain of Maryland, LLC                       Delaware                        Iron Mountain Records Management
----------------------------------------------------------------------------------------------------------------------
IM Billerica, Inc.                                   Massachusetts
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Confidential Destruction LLC           Delaware                        Iron Mountain Confidential
                                                                                     Destruction
----------------------------------------------------------------------------------------------------------------------
DSI Technology Escrow Services, Inc.                 Delaware                        DSI
----------------------------------------------------------------------------------------------------------------------
Mountain Real Estate Assets, Inc.                    Delaware
----------------------------------------------------------------------------------------------------------------------
Mountain West Palm Real Estate, Inc.                 Delaware
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Records Management                     Puerto Rico                     Iron Mountain Records Management
(Puerto Rico), Inc.
----------------------------------------------------------------------------------------------------------------------
COMAC, Inc.                                          Delaware                        COMAC
----------------------------------------------------------------------------------------------------------------------
Arcus Data Security, Inc.                            Delaware                        Arcus Data Security
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Global, Inc.                           Delaware
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Global, LLC                            Delaware
----------------------------------------------------------------------------------------------------------------------
Arcus Data Security, LLC                             Delaware                        Arcus Data Security
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Mexico, S.A. de R.L. de C.V.           Mexico
----------------------------------------------------------------------------------------------------------------------
Sistemas de Archivo Corporativo S.A. de              Mexico
R.L. de C.V.
----------------------------------------------------------------------------------------------------------------------
Sistemas de Archivo, S.A. de R.L. de C.V.            Mexico
----------------------------------------------------------------------------------------------------------------------
Sistemas de Archivo de Mexico, S.A. de               Mexico
R.L. de C.V.
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Cayman Ltd.                            Cayman Islands
----------------------------------------------------------------------------------------------------------------------
Iron Mountain South America, Ltd.                    Cayman Islands
----------------------------------------------------------------------------------------------------------------------
IMSA Peru SRL                                        Peru
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Chile S.A.                             Chile
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Peru S.A.                              Peru
----------------------------------------------------------------------------------------------------------------------
Immobiliaria E Inversiones La Primareva LTDA         Chile
----------------------------------------------------------------------------------------------------------------------
Custodia de Documentos LTDA de Archivas LTDA         Chile
----------------------------------------------------------------------------------------------------------------------
Almacenaje Y Administracion De Archivos LTDA         Chile
----------------------------------------------------------------------------------------------------------------------
Iron Mountain du Brazil Emprendimentos Ltda.         Brazil                          Iron Mountain
----------------------------------------------------------------------------------------------------------------------
Iron Mountain du Brazil SA                           Brazil
----------------------------------------------------------------------------------------------------------------------
C.A.D.A. Storage S.A.                                Argentina
----------------------------------------------------------------------------------------------------------------------
Box Security                                         Argentina
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Canada Corporation                     Nova Scotia                     Iron Mountain
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Box Company                            Nova Scotia
----------------------------------------------------------------------------------------------------------------------
Archivex Limited                                     Nova Scotia
----------------------------------------------------------------------------------------------------------------------
Archivex Box Company Limited                         Nova Scotia
----------------------------------------------------------------------------------------------------------------------
FACS Records Centre Inc.                             British Columbia                Iron Mountain
----------------------------------------------------------------------------------------------------------------------
397499 British Columbia Ltd.                         British Columbia
----------------------------------------------------------------------------------------------------------------------
326252 British Columbia Ltd.                         British Columbia
----------------------------------------------------------------------------------------------------------------------
Pierce Leahy Europe Limited                          United Kingdom
----------------------------------------------------------------------------------------------------------------------
PLRH, Inc.                                           Pennsylvania
----------------------------------------------------------------------------------------------------------------------
Upper Providence Venture I, L.P.                     Pennsylvania
----------------------------------------------------------------------------------------------------------------------
Iron Mountain (Netherlands) B.V.                     The Netherlands
----------------------------------------------------------------------------------------------------------------------
Iron Mountain (Europe) Group Limited                 United Kingdom
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Europe Limited                         United Kingdom                  Iron Mountain
----------------------------------------------------------------------------------------------------------------------
Stortex (Holdings) Limited                           United Kingdom
----------------------------------------------------------------------------------------------------------------------
Stortex Limited                                      United Kingdom
----------------------------------------------------------------------------------------------------------------------
JAD 93 Limited                                       United Kingdom
----------------------------------------------------------------------------------------------------------------------
Secur Archiv Aktenmanagment                          Germany
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Holdings (Europe) Limited              United Kingdom
----------------------------------------------------------------------------------------------------------------------
Arcus Data Security Limited                          United Kingdom                  Arcus Data Security
----------------------------------------------------------------------------------------------------------------------
The Document Storage Company Limited                 United Kingdom
----------------------------------------------------------------------------------------------------------------------
Silver Sky                                           Channel Islands
----------------------------------------------------------------------------------------------------------------------
Datavault Holdings Limited                           United Kingdom
----------------------------------------------------------------------------------------------------------------------
Datavault Limited                                    Scotland
----------------------------------------------------------------------------------------------------------------------
Datavault Northwest Limited                          United Kingdom
----------------------------------------------------------------------------------------------------------------------
Datavault Southwest Limited                          United Kingdom
----------------------------------------------------------------------------------------------------------------------
Iron Mountain (UK) Limited                           United Kingdom                  Iron Mountain
----------------------------------------------------------------------------------------------------------------------
Document and Information Management                  United Kingdom
Services Ltd.
----------------------------------------------------------------------------------------------------------------------
Kestrel Data Services Limited                        United Kingdom
----------------------------------------------------------------------------------------------------------------------
Miller Data Management Limited                       United Kingdom
----------------------------------------------------------------------------------------------------------------------
Kestrel Data UK Limited                              United Kingdom
----------------------------------------------------------------------------------------------------------------------
Kestrel Data Storage and Management Limited          United Kingdom
----------------------------------------------------------------------------------------------------------------------
Kestrel Reprographics Limited                        United Kingdom
----------------------------------------------------------------------------------------------------------------------
Memogarde S.A.                                       France
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Holdings (France) SNC                  France
----------------------------------------------------------------------------------------------------------------------
Iron Mountain (France) S.A.                          France
----------------------------------------------------------------------------------------------------------------------
MAP S.A.                                             France
----------------------------------------------------------------------------------------------------------------------
BDM S.A.                                             France
----------------------------------------------------------------------------------------------------------------------
FIME S.A.                                            France
----------------------------------------------------------------------------------------------------------------------
France Telesauvgarde S.A.                            France
----------------------------------------------------------------------------------------------------------------------
Societe Civile Immobiliare de Chemin Cornillion      France
----------------------------------------------------------------------------------------------------------------------
Iron Mountain Espana, S.A.                           Spain
----------------------------------------------------------------------------------------------------------------------
Boston Data, S.A.                                    Spain
----------------------------------------------------------------------------------------------------------------------
Documenetalia, S.A.                                  Spain
----------------------------------------------------------------------------------------------------------------------
Innovator Projects, S.A.                             Spain
----------------------------------------------------------------------------------------------------------------------
Datavault, S.A.                                      Spain
----------------------------------------------------------------------------------------------------------------------
Datavault Iberica, S.A.                              Spain
----------------------------------------------------------------------------------------------------------------------
Datavault Madrid, S.A.                               Spain
----------------------------------------------------------------------------------------------------------------------
Datavault Cantabrico, S.A.                           Spain
----------------------------------------------------------------------------------------------------------------------
Databox Aragon S.A.                                  Spain
----------------------------------------------------------------------------------------------------------------------
Databox Andalucia, S.A.                              Spain
----------------------------------------------------------------------------------------------------------------------
MGR Arrendamientos Industriales, S.L.                Spain
----------------------------------------------------------------------------------------------------------------------
</TABLE>


