Exhibit 99.1

                           IRON MOUNTAIN INCORPORATED


                          FORM OF LETTER OF TRANSMITTAL

                          8 3/4% SENIOR NOTES DUE 2009

     THE EXCHANGE OFFER WILL EXPIRE AT 5:00 P.M., NEW YORK CITY TIME, ON 
UNLESS EXTENDED (THE "EXPIRATION DATE").

                             The Exchange Agent is:

                              THE BANK OF NEW YORK

   By Registered or Certified Mail:             By Hand or Overnight Delivery:

         The Bank of New York                        The Bank of New York
        101 Barclay Street - 7E                       101 Barclay Street
       New York, New York 10286                Corporate Trust Services Window
       Attention: Natalie Simon                         Ground Level
        Reorganization Section                     New York, New York 10286
                                                   Attention: Natalie Simon
                                                    Reorganization Section


                            By Facsimile for Eligible
                                  Institutions:
                                 (212) 815-6339

                             For confirmation and/or
                                information call:
                                 (212) 815-5788

         Delivery of this instrument to an address other than as set forth above
or transmission of instructions via a facsimile number other than the one listed
above will not constitute a valid delivery. The instructions accompanying this
Letter of Transmittal should be read carefully before this Letter of Transmittal
is completed.

         The undersigned acknowledges that he or she has received the Prospectus
dated December   , 1997 (the "Prospectus") of Iron Mountain Incorporated (the 
"Company") and this Letter of Transmittal (the "Letter of Transmittal"), which 
together constitute the Company's offer (the "Exchange Offer") to exchange 
$1,000 principal amount (or integral multiples in excess thereof) of its 8 3/4%
Senior Notes due 2009, (the "New Notes"), which have been registered under the
Securities Act of 1933, as amended (the "Securities Act"), pursuant to a
Registration Statement of which the Prospectus is a part, for each $1,000
principal amount (or integral multiples in excess thereof) of its outstanding 
8-3/4% Senior Notes due 2009 (the "Old Notes"), of which $250,000,000 aggregate
principal amount is outstanding. Other capitalized terms used but not defined
herein have the meaning given to them in the Prospectus.






                                        2

         The Letter of Transmittal is to be used by Holders of Old Notes (i) if
the Old Notes are to be physically delivered herewith; (ii) if delivery of the
Old Notes is made by book-entry transfer to the Exchange Agent's account at the
Depositary Trust Company ("DTC") pursuant to the procedures set forth in the
Prospectus under "The Exchange Offer--Procedures for Tendering" by any financial
institution that is a participant in DTC and whose name appears on a security
position listing as the owner of the Old Notes or (iii) if the guaranteed
delivery procedures described in the Prospectus are to be utilized. DELIVERY OF
DOCUMENTS TO DTC DOES NOT CONSTITUTE DELIVERY TO THE EXCHANGE AGENT.

         The term "Holder" with respect to the Exchange Offer means any person
(i) in whose name Old Notes are registered on the books of the Company or any
other person who has obtained a properly completed bond power from the
registered holder or (ii) in whose name the Old Notes are held of record by DTC
who desires to deliver such Old Notes by book-entry transfer at DTC. The
undersigned has completed, executed and delivered this Letter of Transmittal to
indicate the action the undersigned desires to take with respect to the Exchange
Offer. Holders who wish to tender their Old Notes must complete this letter in
its entirety.

         Holders who desire to tender their Old Notes and whose Old Notes are
not lost but are not immediately available or who cannot deliver their Old Notes
and all other documents required hereby to the Exchange Agent by the Expiration
Date or who are unable to complete the procedure for book-entry transfer on a
timely basis must tender their Old Notes pursuant to the guaranteed delivery
procedure set forth in "The Exchange Offer--Procedures for Tendering."






                                        3


     PLEASE READ THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL
CAREFULLY BEFORE CHECKING ANY BOX BELOW.


             DESCRIPTION OF 8 3/4% SENIOR NOTES DUE 2009 (OLD NOTES)





                                                                                                  Principal Amount
                                                                                                Tendered (must be in
         Name(s) and                                                                              denominations of
        Address(es) of                                            Aggregate Principal          $1,000 or any integral
     Registered Holder(s)               Certificate                Amount Represented           multiples in excess
  (Please fill in, if blank)             Number(s)*                by Certificate(s)                thereof )**
- --------------------------------------------------------------------------------------------------------------------------
                                                                                      


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                                           Total
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*        Need not be completed by holders of Old Notes who tender by book-entry transfer.

**       Need not be completed by holders who wish to tender with respect to all Old Notes listed.
- --------------------------------------------------------------------------------------------------------------------------




NOTE:  SIGNATURES MUST BE PROVIDED BELOW.  PLEASE READ THE ACCOMPANYING
INSTRUCTIONS CAREFULLY.

[ ]   CHECK HERE IF TENDERED OLD NOTES ARE BEING DELIVERED BY BOOK-ENTRY
      TRANSFER MADE TO THE ACCOUNT MAINTAINED BY THE EXCHANGE AGENT WITH DTC AND
      COMPLETE THE FOLLOWING:

Name of Tendering Institution:__________________________________________________

DTC Book-Entry Account Number:__________________________________________________

Transaction Code No:____________________________________________________________

[ ] CHECK HERE IF TENDERED OLD NOTES ARE BEING DELIVERED PURSUANT TO
A NOTICE OF GUARANTEED DELIVERY PREVIOUSLY SENT TO THE EXCHANGE
AGENT AND COMPLETE THE FOLLOWING:

Name(s) of Registered  Holder(s):_______________________________________________

Date of Execution of Notice of Guaranteed Delivery:_____________________________

  Name of Institution which Guaranteed Delivery:________________________________

  DTC Account Number:___________________________________________________________

  If Delivered by Book-Entry Transfer:__________________________________________

  Name of Tendering Institution:________________________________________________

  DTC Book-Entry Account No.:___________________________________________________

  Transaction Code No.:_________________________________________________________





                                        4

[ ]    CHECK HERE IF YOU ARE A BROKER-DEALER TENDERING OLD NOTES ACQUIRED AS A
       RESULT OF MARKET-MAKING OR OTHER TRADING ACTIVITIES AND WISH TO RECEIVE
       10 ADDITIONAL COPIES OF THE PROSPECTUS AND 10 COPIES OF ANY AMENDMENTS 
       OR SUPPLEMENTS THERETO.

         Name:____________________

         Address:_________________

                 _________________


              PLEASE READ THE ACCOMPANYING INSTRUCTIONS CAREFULLY




                                        5

To: The Bank of New York


Ladies and Gentlemen:

         Subject to the terms and conditions of the Exchange Offer, the
undersigned hereby tenders to the Company the principal amount of Old Notes
indicated above. Subject to and effective upon the acceptance for exchange of
the principal amount of Old Notes tendered in accordance with this Letter of
Transmittal, the undersigned sells, assigns and transfers to, or upon the order
of, the Company all right, title and interest in and to the Old Notes tendered
hereby. The undersigned hereby irrevocably constitutes and appoints the Exchange
Agent its agent and attorney-in-fact (with full knowledge that the Exchange
Agent also acts as the agent of the Company) with respect to the tendered Old
Notes with full power of substitution to (i) deliver such Old Notes to the
Company or transfer ownership of such Old Notes on the account books maintained
by DTC, in each case, together with all accompanying evidences of transfer and
authenticity to, or upon the order of, the Company, (ii) present such Old Notes
or transfer ownership of such Old Notes on the account books maintained by DTC,
for transfer on the books of the Company and (iii) receive all benefits and
otherwise exercise all rights of beneficial ownership of such Old Notes, all in
accordance with the terms of the Exchange Offer. The power of attorney granted
in this paragraph shall be deemed irrevocable and coupled with an interest.

         The undersigned hereby represents and warrants that he or she has full
power and authority to tender, sell, assign and transfer the Old Notes tendered
hereby and that the Company will acquire good and unencumbered title thereto,
free and clear of all liens, restrictions, charges and encumbrances and not
subject to any adverse claim, when the same are acquired by the Company. The
undersigned hereby acknowledges that this Exchange Offer is being made in
reliance upon an interpretation by the staff of the Securities and Exchange
Commission that any New Notes acquired in exchange for Old Notes tendered hereby
may be offered for sale, resold and otherwise transferred by holders thereof
(other than any such Holder that is an "affiliate" of the Company or any of its
subsidiaries within the meaning of Rule 405 under the Securities Act of 1933
(the "Securities Act")), without compliance with the registration and prospectus
delivery provisions of the Securities Act, provided that such New Notes are
acquired in the ordinary course of business of the Holder receiving such New
Notes and that neither the Holder nor any such other person has an arrangement
with any person to participate in the distribution of such New Notes. The
undersigned hereby further represents that (i) the New Notes acquired pursuant
to the Exchange Offer are being obtained in the ordinary course of such Holder's
business, (ii) such Holder has no arrangements with any person to participate in
the distribution (within the meaning of the Securities Act) of such New Notes
and (iii) such Holder is not an "affiliate", as defined under Rule 405 of the
Securities Act of the Company or any of its subsidiaries or, if such Holder is
an affiliate, that such Holder will comply with the registration and prospectus
delivery requirements of the Securities Act to the extent applicable. If the
undersigned is not a broker-dealer, the undersigned represents that it is not
engaged in, and does not intend to engage in, a distribution of New Notes. If
the undersigned is a broker-dealer that will receive New Notes for its own
account in exchange for Old Notes that were acquired as a result of
market-making activities or other trading activities, it acknowledges that it
will deliver a prospectus in connection with any resale of such New Notes;
however, by so acknowledging and by delivering a prospectus, the undersigned
will not be deemed to admit that it is an "underwriter" within the meaning of
the Securities Act. The undersigned will, upon request, execute and deliver any
additional documents deemed by the Exchange Agent or the Company to be necessary
or desirable to complete the assignment, transfer and purchase of the Old Notes
tendered hereby.

         For purposes of the Exchange Offer, the Company shall be deemed to have
accepted validly tendered Old Notes, when, as and if the Company has given oral
or written notice of acceptance thereof to the Exchange Agent.






                                        6

         If any tendered Old Notes are not accepted for exchange pursuant to the
Exchange Offer for any reason, any such unaccepted Old Notes will be returned
(except as noted below with respect to tenders through DTC), without expense, to
the undersigned at the address shown below or at a different address as may be
indicated herein under "Special Payment Instructions" as promptly as practicable
after the Expiration Date.

         All authority herein conferred or agreed to be conferred in this Letter
of Transmittal shall survive the death, incapacity or dissolution of the
undersigned, and any obligation of the undersigned hereunder shall be binding
upon the administrators, legal representatives, heirs, personal representatives,
successors and assigns of the undersigned.

         The undersigned understands that tenders of Old Notes pursuant to the
procedures described under the caption "The Exchange Offer--Procedures for
Tendering" in the Prospectus and in the instructions hereto will constitute a
binding agreement between the undersigned and the Company upon the terms and
subject to the conditions of the Exchange Offer.

         Unless otherwise indicated under "Special Payment Instructions," please
issue the New Notes issued in exchange for the Old Notes accepted for exchange
and return any Old Notes not tendered or not exchanged in the name(s) of the
undersigned (or, in either such event, in the case of Old Notes tendered by DTC,
by credit to the account at DTC). Similarly, unless otherwise indicated under
"Special Delivery Instructions," please send the New Notes issued in exchange
for the Old Notes accepted for exchange and any Old Notes not tendered or not
exchanged (and accompanying documents, as appropriate) to the undersigned at the
address shown below the undersigned's signature(s), unless, in either event,
tender is being made through DTC. In the event that both "Special Payment
Instructions" and "Special Delivery Instructions" are completed, please issue
the New Notes issued in exchange for the Old Notes accepted for exchange and
return any Old Notes not tendered or not exchanged in the name(s) of, and send
said New Notes to, the person(s) so indicated. The undersigned recognizes that
the Company has no obligation pursuant to the "Special Payment Instructions" and
"Special Delivery Instructions" to transfer any Old Notes from the name of the
registered holder(s) thereof if the Company does not accept for exchange any of
the Old Notes so tendered.

         Holders of the Old Notes who wish to tender their Old Notes and (i)
whose Old Notes are not immediately available or (ii) who cannot deliver their
Old Notes, this Letter of Transmittal or any other documents required hereby to
the Exchange Agent prior to the Expiration Date, may tender their Old Notes
according to the guaranteed delivery procedures set forth in the Prospectus
under the caption "The Exchange Offer--Guaranteed Delivery Procedures." See
Instruction 1 regarding the completion of the Letter of Transmittal printed
below.








                                        7


                          SPECIAL DELIVERY INSTRUCTIONS
                          (See Instructions 3, 4 and 5)

To be completed ONLY if certificates for Old Notes in a principal amount not
tendered or not purchased, or New Notes issued in exchange for Old Notes
accepted for exchange are to be sent to someone other than the undersigned, or
the undersigned at an address other than that shown above.

Mail to:

Name:______________________________________
    (Please Print)

Address:___________________________________

___________________________________________

___________________________________________

___________________________________________
      (Include Zip Code)

___________________________________________
(Tax Identification or Social Security No.)




                          SPECIAL PAYMENT INSTRUCTIONS
                          (See Instructions 3, 4 and 5)

To be completed ONLY if certificates for Old Notes in a principal amount not
tendered or not purchased, or New Notes issued in exchange for Old Notes
accepted for exchange, are to be issued in the name of someone other than the
undersigned.


Issue New Notes to:

Name:______________________________________
    (Please Print)

Address:___________________________________

___________________________________________

___________________________________________

___________________________________________
      (Include Zip Code)

___________________________________________
(Tax Identification or Social Security No.)



IMPORTANT: THIS LETTER OR A FACSIMILE HEREOF (TOGETHER WITH THE CERTIFICATES FOR
OLD NOTES OR A BOOK-ENTRY CONFIRMATION AND ALL OTHER REQUIRED DOCUMENTS OR THE
NOTICE OF GUARANTEED DELIVERY) MUST BE RECEIVED BY THE EXCHANGE AGENT PRIOR TO
5:00 P.M., NEW YORK CITY TIME, ON THE EXPIRATION DATE.

                 PLEASE READ THIS ENTIRE LETTER OF TRANSMITTAL
                   CAREFULLY BEFORE COMPLETING ANY BOX ABOVE.





                                        8


 PLEASE SIGN HERE WHETHER OR NOT OLD NOTES ARE BEING PHYSICALLY TENDERED HEREBY

______________________________________________ Dated: __________________________

______________________________________________ Dated: __________________________
Signature(s) of Registered Holder(s) or Authorized Signatory

Area Code and Telephone Number: ________________________________________________

         The above lines must be signed by the registered holder(s) of Old Notes
as their name(s) appear(s) on the Old Notes or, if tendered by a participant in
DTC, exactly as such participant's name appears on a security position listing
as the owner of the Old Notes or by person(s) authorized to become registered
holder(s) by properly executed bond power and other documents transmitted with
this Letter of Transmittal. If Old Notes to which this Letter of Transmittal
relates are held of record by two or more joint holders, then all such holders
must sign this Letter of Transmittal. If signature is by a trustee, executor,
administrator, guardian, attorney-in-fact, officer of a corporation or other
person acting in a fiduciary or representative capacity, such person must (i)
set forth his or her full title below and (ii) unless waived by the Company,
submit evidence satisfactory to the Company of such person's authority so to
act. See Instruction 3 regarding the completion of this Letter of Transmittal
printed below.

         If the signature appearing above is not the registered Holder(s) of the
Old Notes, then the registered Holder must sign a valid proxy.

Name(s):________________________________________________________________________


________________________________________________________________________________
                                 (Please Print)

Capacity (full title):__________________________________________________________


Address:________________________________________________________________________


________________________________________________________________________________
                               (Include Zip Code)

                            GUARANTEE OF SIGNATURE(S)
                        (If required - See Instruction 3)

Authorized Signature:___________________________________________________________

Name:___________________________________________________________________________
                                 (Please Print)

Name of Firm:___________________________________________________________________

Address:________________________________________________________________________


________________________________________________________________________________
                               (Include Zip Code)

Title:__________________________________________________________________________

Area Code and Telephone No.:____________________________________________________

Dated:__________________________________________________________________________






                                        9


                                  INSTRUCTIONS

                    FORMING PART OF THE TERMS AND CONDITIONS
                              OF THE EXCHANGE OFFER

         1. Delivery of this Letter of Transmittal and Old Notes. The tendered
Old Notes (or a confirmation of a book-entry transfer into the Exchange Agent's
account at DTC of all Old Notes delivered electronically), as well as a properly
completed and duly executed copy of this Letter of Transmittal or facsimile
hereof and any other documents required by this Letter of Transmittal, must be
received by the Exchange Agent at its address set forth herein prior to 5:00
p.m., New York City time, on the Expiration Date. The method of delivery of the
tendered Old Notes, this Letter of Transmittal and all other required documents
to the Exchange Agent is at the election and risk of the Holder and, except as
otherwise provided below, the delivery will be deemed made only when actually
received by the Exchange Agent. Instead of delivery by mail, it is recommended
that the Holder use an overnight or hand delivery service. In all cases,
sufficient time should be allowed to assure timely delivery. No Letter of
Transmittal or Old Notes should be sent to the Company.

         Holders who wish to tender their Old Notes and (i) whose Old Notes are
not immediately available, or (ii) who cannot deliver their Old Notes, this
Letter of Transmittal or any other documents required hereby to the Exchange
Agent prior to 5:00 p.m., New York City time, on the Expiration Date, must
tender their Old Notes according to the guaranteed delivery procedures set forth
in the Prospectus. Pursuant to such procedures: (i) such tender must be made by
or through a member firm of a registered national securities exchange or of the
National Association of Securities Dealers, Inc., or a commercial bank or trust
company having an office or correspondent in the United States or an "eligible
guarantor institution" (an "Eligible Institution") within the meaning of Rule
17Ad-15 under the Securities Exchange Act of 1934, as amended; (ii) prior to the
Expiration Date, the Exchange Agent must have received from the Eligible
Institution a properly completed and duly executed Notice of Guaranteed Delivery
(by facsimile transmission, mail or hand delivery) setting forth the name and
address of the Holder of the Old Notes, the certificate number or numbers of
such Old Notes and the principal amount of Old Notes tendered, stating that the
tender is being made thereby and guaranteeing that, within three business days
after the Expiration Date, this Letter of Transmittal (or facsimile hereof)
together with the Old Notes (or a confirmation of electronic delivery of
book-entry delivery into the Exchange Agent's account at DTC) and any other
required documents will be deposited by the Eligible Institution with the
Exchange Agent; and (iii) such properly completed and executed Letter of
Transmittal (or facsimile hereof), as well as all other documents required by
this Letter of Transmittal and all tendered Old Notes in proper form for
transfer (or a confirmation of electronic delivery of book-entry delivery into
the Exchange Agent's account at DTC), must be received by the Exchange Agent
within three business days after the Expiration Date, all as provided in the
Prospectus under the caption "The Exchange Offer -- Guaranteed Delivery
Procedures." Any Holder of Old Notes who wishes to tender his or her Old Notes
pursuant to the guaranteed delivery procedures described above must ensure that
the Exchange Agent receives the Notice of Guaranteed Delivery prior to 5:00
p.m., New York City time, on the Expiration Date. Upon request of the Exchange
Agent, a Notice of Guaranteed Delivery will be sent to Holders who wish to
tender their Old Notes according to the guaranteed delivery procedures set forth
above.

         All questions as to the validity, form, eligibility (including time of
receipt) and acceptance of tendered Old Notes and withdrawal of tendered Old
Notes will be determined by the Company in its sole discretion, which
determination will be final and binding. The Company reserves the absolute right
to reject any and all Old Notes not properly tendered or any Old Notes the
Company's acceptance of which would, in the opinion of counsel for the Company,
be unlawful. The Company also reserves the right to waive any defects or
irregularities or conditions of tender as to the Exchange Offer and/or
particular Old Notes. The Company's interpretation of the terms and conditions
of the Exchange Offer (including the instructions in this Letter of Transmittal)
shall be final and binding on all parties. Unless waived, any defects or
irregularities in connection with tenders of Old Notes must be cured within such
time as the





                                       10


Company shall determine. Neither the Company, the Exchange Agent nor any other
person shall be under any duty to give notification of defects or irregularities
with respect to tenders of Old Notes, nor shall any of them incur any liability
for failure to give such notification. Tenders of Old Notes will not be deemed
to have been made until such defects or irregularities have been cured or
waived. Any Old Notes received by the Exchange Agent that are not validly
tendered and as to which the defects or irregularities have not been cured or
waived will be returned by the Exchange Agent to the tendering Holders of Old
Notes, unless otherwise provided in this Letter of Transmittal, as soon as
practicable following the Expiration Date.

         2. Partial Tenders. Tenders of Old Notes will be accepted only in
denominations of $1,000 and any integral multiples in excess thereof. If less
than the entire principal amount of any Old Notes is tendered, the tendering
Holder should fill in the principal amount tendered in the fourth column of the
box entitled "Description of 8 3/4% Senior Notes Due 2009 (Old Notes)" above.
The entire principal amount of Old Notes delivered to the Exchange Agent will be
deemed to have been tendered unless otherwise indicated. If the entire principal
amount of all Old Notes is not tendered, then Old Notes for the principal amount
of Old Notes not tendered and the New Notes issued in exchange for any Old Notes
accepted will be sent to the Holder at his or her registered address, unless a
different address is provided in the appropriate box on this Letter of
Transmittal, promptly after the Old Notes are accepted for exchange.

         3. Signatures on the Letter of Transmittal; Bond Powers and
Endorsements; Guarantee of Signatures. If this Letter of Transmittal (or
facsimile hereof) is signed by the record Holder(s) of the Old Notes tendered
hereby, the signature must correspond with the name(s) as written on the face of
the Old Notes without alteration, enlargement or any change whatsoever.

         If this Letter of Transmittal (or facsimile hereof) is signed by the
registered Holder or Holders of Old Notes tendered and the New Notes issued in
exchange therefor are to be issued (or any untendered principal amount of Old
Notes is to be reissued) to the registered Holder, the said Holder need not and
should not endorse any tendered Old Notes, nor provide a separate bond power.

         If this Letter of Transmittal (or facsimile hereof) is signed by a
person other than the registered Holder or Holders of any Old Notes listed, such
Old Notes must be endorsed or accompanied by appropriate bond powers signed as
the name of the registered Holder or Holders appears on the Old Notes.

         If this Letter of Transmittal (or facsimile hereof) or any Old Notes or
bond powers are signed by trustees, executors, administrators, guardians,
attorneys-in-fact or officers of corporations or others acting in a fiduciary or
representative capacity, such persons should so indicate when signing, and,
unless waived by the Company, evidence satisfactory to the Company of their
authority so to act must be submitted with this Letter of Transmittal.

         Endorsements on Old Notes or signatures on bond powers required by this
Instruction 3 must be guaranteed by an Eligible Institution participating in a
recognized medallion signature guarantee program.

         Except as otherwise provided below, all signatures on this Letter of
Transmittal (or facsimile hereof) must be guaranteed by an Eligible Institution
participating in a recognized medallion signature guarantee program. Signatures
on this Letter of Transmittal need not be guaranteed if (i) this Letter of
Transmittal is signed by the registered Holder(s) of the Old Notes tendered
herewith (including any participant in DTC whose name appears on a security
position listing as the owner of Old Notes) and such Holder(s) have not
completed the box set forth herein entitled "Special Payments Instructions" or
the box entitled "Special Delivery Instructions" or (ii) such Old Notes are
tendered for the account of an Eligible Institution.






                                       11

         4. Special Issuance and Delivery Instructions. Tendering Holders should
indicate, in the applicable box or boxes, the name and address to which New
Notes or substitute Old Notes for principal amounts not tendered or not accepted
for exchange are to be issued or sent, if different from the name and address of
the person signing this Letter of Transmittal (or in the case of tender of the
Old Notes through DTC, if different from DTC). In the case of issuance in a
different name, the taxpayer identification or social security number of the
person named must also be indicated.

         5. Tax Identification Number. Federal income tax law requires that a
Holder whose offered Old Notes are accepted for exchange must provide the
Company (as payor) with his, her or its correct Taxpayer Identification Number
("TIN"), which, in the case of an exchanging Holder who is an individual, is his
or her social security number. If the Company is not provided with the correct
TIN or an adequate basis for exemption, such Holder may be subject to a $50
penalty imposed by the Internal Revenue Service (the "IRS"). In addition,
delivery to such Holder of New Notes may be subject to backup withholding in an
amount equal to 31% of the gross proceeds resulting from the Exchange Offer. If
withholding results in an overpayment of taxes, a refund may be obtained. Exempt
Holders (including, among others, all corporations and certain foreign
individuals) are not subject to these backup withholding and reporting
requirements.

         To prevent backup withholding, each exchanging Holder must provide his,
her or its correct TIN by completing the Substitute Form W-9 enclosed herewith,
certifying that the TIN provided is correct (or that such Holder is awaiting a
TIN) and that either (i) the Holder is exempt from backup withholding, (ii) the
Holder has not been notified by the IRS that he, she or it is subject to backup
withholding as a result of a failure to report all interest or dividends, or
(iii) the IRS has notified the Holder that he, she or it is no longer subject to
backup withholding. In order to satisfy the Exchange Agent that a foreign
individual qualifies as an exempt recipient, such Holder must submit a statement
signed under penalty of perjury attesting to such exempt status. Such statements
may be obtained from the Exchange Agent. If the Old Notes are in more than one
name or are not in the name of the actual owner, consult the Substitute Form W-9
for information on which TIN to report. If you do not provide your TIN to the
Company within 60 days, backup withholding will begin and continue until you
furnish your TIN to the Company.

         6. Transfer Taxes. The Company will pay all transfer taxes, if any,
applicable to the exchange of Old Notes pursuant to the Exchange Offer. If,
however, New Notes or Old Notes for principal amounts not tendered or accepted
for exchange are to be delivered to, or are to be registered or issued in the
name of, any person other than the registered Holder of the Old Notes tendered
hereby, or if tendered Old Notes are registered in the name of any person other
than the person signing this Letter of Transmittal, or if a transfer tax is
imposed for any reason other than the exchange of Old Notes pursuant to the
Exchange Offer, then the amount of any such transfer taxes (whether imposed on
the registered Holder or on any other person) will be payable by the tendering
Holder.

         Except as provided in this Instruction 6, it will not be necessary for
transfer tax stamps to be affixed to the Old Notes listed in this Letter of
Transmittal.

         7. Waiver of Conditions. The Company reserves the absolute right to
amend, waive or modify specified conditions in the Exchange Offer in the case of
any Old Notes tendered.

         8. Mutilated, Lost Stolen or Destroyed Old Notes. Any tendering Holder
whose Old Notes have been mutilated, lost, stolen or destroyed should contact
the Exchange Agent at the address indicated herein for further instructions.

         9. Requests for Assistance or Additional Copies. Questions and requests
for assistance and requests for additional copies of the Prospectus or this
Letter of Transmittal may be directed to the Exchange Agent at the address
specified above. The telephone number for the Exchange Agent is (212) 815-5788.
Holders may also contact their broker, dealer, commercial bank, trust company or
other nominee for assistance concerning the Exchange Offer.






                                       12


                          (DO NOT WRITE IN SPACE BELOW)
- --------------------------------------------------------------------------------
 Certificate                        Old Notes                          Old Notes
 Surrendered                        Tendered                            Accepted
- --------------------------------------------------------------------------------


- --------------------------------------------------------------------------------


- --------------------------------------------------------------------------------


- --------------------------------------------------------------------------------

Delivery Prepared By: _________________ Checked By: _____________ Dated:________







                                       14



                    PAYOR'S NAME: Iron Mountain Incorporated


                                                                           

                           PART I -- PLEASE PROVIDE YOUR TIN IN
        SUBSTITUTE         THE BOX AT RIGHT AND CERTIFY BY                        ____________________________
         Form W-9          SIGNING AND DATING BELOW                                  Social Security Number

                                                                                               OR

                                                                                  ----------------------------
                                                                                 Employer Identification Number

                           PART II -- Certification--Under penalties of perjury,
                           I certify that:
      Department of
       the Treasury        (1)   The number shown on this form is my correct 
     Internal Revenue            Taxpayer Identification Number (or I am 
         Service                 waiting for a number to be issued to me), and

                           (2)   I am not subject to backup withholding because
                                 (i) I am exempt from backup withholding, (ii)
                                 I have not been notified by the Internal
                                 Revenue Service ("IRS") that I am subject to
                                 backup withholding as a result of a failure to
                                 report all interest or dividends, or (iii) the
                                 IRS has notified me that I am no longer
                                 subject to backup withholding.
- --------------------------------------------------------------------------------

                           Certification Instructions--You must cross out item (2) in Part II above
     Payer's Request       if you have been notified by the IRS that you are subject to backup
       for Taxpayer        withholding because of underreporting interest or dividends on your tax
      Identification       return.  However, if after being notified by the IRS that you were subject
       Number (TIN)        to backup withholding you received another notification from the IRS             PART III
                           that you are no longer subject to backup withholding, do not cross out
                           item (2).                                                                      Awaiting TIN [ ]

                           Signature:___________________________  Date:_________
                           Name (Please Print):_________________________________




     NOTE: FAILURE TO COMPLETE AND RETURN THE SUBSTITUTE FORM W-9 MAY RESULT IN
BACKUP WITHHOLDING OF 31% OF ANY PAYMENTS MADE TO YOU. PLEASE REVIEW THE
ENCLOSED GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION NUMBER ON
SUBSTITUTE FORM W-9 FOR ADDITIONAL DETAILS.

                   YOU MUST COMPLETE THE FOLLOWING CERTIFICATE
           IF YOU CHECKED THE BOX IN PART III OF SUBSTITUTE FORM W-9.


             CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER

         I certify under penalties of perjury that a taxpayer identification
number has not been issued to me, and either (i) I have mailed or delivered an
application to receive a taxpayer identification number to the appropriate
Internal Revenue Service Center or Social Security Administration Office or (ii)
I intend to mail or deliver an application in the near future. I understand that
if I do not provide a taxpayer identification number within 60 days, 31% of all
reportable payments made to me thereafter will be withheld until I provide a
number.

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                 Signature                                   Date
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             Name (Please Print)