
<PAGE>
 
THIS NOTE HAS NOT BEEN REGISTERED UNDER THE U.S. SECURITIES ACT OF 1933, AS
AMENDED (THE "ACT"), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD WITHIN THE
UNITED STATES OR TO, OR FOR THE ACCOUNT OR BENEFIT OF, U.S. PERSONS, EXCEPT AS
SET FORTH BELOW.  BY ITS ACQUISITION HEREOF, THE HOLDER (1) REPRESENTS THAT (A)
IT IS A "QUALIFIED INSTITUTIONAL BUYER" (AS DEFINED IN RULE 144A UNDER THE ACT)
OR (B) IT IS AN "ACCREDITED INVESTOR" (AS DEFINED IN RULE 501(a)(1), (2), (3) OR
(7) UNDER THE ACT) (AN "ACCREDITED INVESTOR") OR (C) IT IS NOT A U.S. PERSON AND
IS ACQUIRING THIS NOTE IN AN OFFSHORE TRANSACTION, (2) AGREES THAT IT WILL NOT
WITHIN THREE YEARS AFTER THE ORIGINAL ISSUANCE OF THIS NOTE RESELL OR OTHERWISE
TRANSFER THIS NOTE EXCEPT (A) TO THE COMPANY OR ANY SUBSIDIARY THEREOF, (B)
INSIDE THE UNITED STATES TO A QUALIFIED INSTITUTIONAL BUYER IN COMPLIANCE WITH
RULE 144A UNDER THE ACT, (C) INSIDE THE UNITED STATES TO AN ACCREDITED INVESTOR
THAT, PRIOR TO SUCH TRANSFER, FURNISHES (OR HAS FURNISHED ON ITS BEHALF BY A
U.S. BROKER-DEALER) TO THE TRUSTEE A SIGNED LETTER CONTAINING CERTAIN
REPRESENTATIONS AND AGREEMENTS RELATING TO THE RESTRICTIONS ON TRANSFER OF THIS
NOTE (THE FORM OF WHICH LETTER CAN BE OBTAINED FROM THE TRUSTEE), (D) OUTSIDE
THE UNITED STATES IN AN OFFSHORE TRANSACTION IN COMPLIANCE WITH RULE 904 UNDER
THE ACT, (E) PURSUANT TO THE EXEMPTION FROM REGISTRATION PROVIDED BY RULE 144
UNDER THE ACT (IF AVAILABLE) OR (F) PURSUANT TO AN EFFECTIVE REGISTRATION
STATEMENT UNDER THE ACT AND (3) AGREES THAT IT WILL GIVE TO EACH PERSON TO WHOM
THIS NOTE IS TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND.
IN CONNECTION WITH ANY TRANSFER OF THIS NOTE WITHIN THREE YEARS AFTER ORIGINAL
ISSUANCE OF THIS NOTE, IF THE PROPOSED TRANSFEREE IS AN ACCREDITED INVESTOR, THE
HOLDER MUST, PRIOR TO SUCH TRANSFER, FURNISH TO THE TRUSTEE AND THE COMPANY SUCH
CERTIFICATIONS, LEGAL OPINIONS OR OTHER INFORMATION AS EITHER OF THEM MAY
REASONABLY REQUIRE TO CONFIRM THAT SUCH TRANSFER IS BEING MADE PURSUANT TO AN
EXEMPTION FROM OR IN A TRANSACTION NOT SUBJECT TO THE REGISTRATION REQUIREMENTS
OF THE ACT.  AS USED HEREIN, THE TERMS "OFFSHORE TRANSACTION," "UNITED STATES"
AND "U.S. PERSON" HAVE THE MEANINGS GIVEN TO THEM BY REGULATION S UNDER THE ACT.
<PAGE>
 
THIS NOTE IS A GLOBAL NOTE WITHIN THE MEANING OF THE INDENTURE HEREINAFTER
REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITORY OR A NOMINEE OF A
DEPOSITORY.  THIS NOTE IS NOT EXCHANGEABLE FOR NOTES REGISTERED IN THE NAME OF A
PERSON OTHER THAN THE DEPOSITORY OR ITS NOMINEE EXCEPT IN THE LIMITED
CIRCUMSTANCES DESCRIBED IN THE INDENTURE, AND NO TRANSFER OF THIS NOTE (OTHER
THAN A TRANSFER OF THIS NOTE AS A WHOLE BY THE DEPOSITORY TO A NOMINEE OF THE
DEPOSITORY OR BY A NOMINEE OF THE DEPOSITORY TO THE DEPOSITORY OR ANOTHER
NOMINEE OF THE DEPOSITORY) MAY BE REGISTERED EXCEPT IN THE LIMITED CIRCUMSTANCES
DESCRIBED IN THE INDENTURE.

UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY (A NEW YORK CORPORATION) ("DTC") TO THE ISSUER OR ITS
AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO. OR SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE
OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR
TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO.,
HAS AN INTEREST HEREIN.
<PAGE>
 
R-1                                                     CUSIP Number 720722 AA5



                              PIERCE LEAHY CORP.

                   11 1/8% SENIOR SUBORDINATED NOTE DUE 2006


          Pierce Leahy Corp., a New York corporation (the "Company", which term
includes any successor corporation), for value received promises to pay to CEDE
& CO. or registered assigns the principal sum of $200,000,000 Dollars, on July
15, 2006.

     Interest Payment Dates: January 15 and July 15, commencing January 15, 1997

     Record Dates: January 1 and July 1

          Reference is made to the further provisions of this Note contained
herein, which will for all purposes have the same effect as if set forth at this
place.
<PAGE>
 
          IN WITNESS WHEREOF, the Company has caused this Note to be signed
manually or by facsimile by its duly authorized officers.

                                         PIERCE LEAHY CORP.


                                         By: _________________________________

                                         By: _________________________________

                                         [SEAL]


Certificate of Authentication:
This is one of the 11 1/8% Senior
Subordinated Notes due 2006 referred to in
the within-mentioned Indenture

Dated:

UNITED STATES TRUST COMPANY OF NEW YORK,
as Trustee


By:  ___________________________________
     Authorized Signatory
<PAGE>
 
                              PIERCE LEAHY CORP.

                   11 1/8% SENIOR SUBORDINATED NOTE DUE 2006

1.   INTEREST.

          Pierce Leahy Corp., a New York corporation (the "Company"), promises
to pay interest on the principal amount of this Note semiannually on January 15
and July 15 of each year (each an "Interest Payment Date"), commencing on
January 15, 1997, at the rate of 11 1/8% per annum. Interest will be computed on
the basis of a 360-day year of twelve 30-day months. Interest on the Notes will
accrue from the most recent date to which interest has been paid or, if no
interest has been paid, from the date of the original issuance of the Notes.

          The Company shall pay interest on overdue principal, and on overdue
premium, if any, and overdue interest, to the extent lawful, at the rate equal
to 1% per annum in excess of the rate borne by the Notes.

2.   METHOD OF PAYMENT.

          The Company will pay interest on this Note provided for in Paragraph 1
above (except defaulted interest) to the person who is the registered Holder of
this Note at the close of business on the January 1 or July 1 preceding the
Interest Payment Date (whether or not such day is a Business Day).  The Holder
must surrender this Note to a Paying Agent to collect principal payments.  The
Company will pay principal, premium, if any, and interest in money of the United
States that at the time of payment is legal tender for payment of public and
private debts; provided, however, that the Company may pay principal, premium,
               --------  -------                                              
if any, and interest by check payable in such money.  It may mail an interest
check to the Holder's registered address.

3.   PAYING AGENT AND REGISTRAR.

          Initially, United States Trust Company of New York, a New York
corporation (the "Trustee"), will act as Paying Agent and Registrar.  The
Company may change any Paying Agent or Registrar without notice to the Holders
of the Notes.  Neither the Company nor any of its Subsidiaries or Affiliates may
act as Paying Agent but may act as registrar or co-registrar.

 4.  INDENTURE; RESTRICTIVE COVENANTS.

          The Company issued this Note under an Indenture dated as of July 15,
1996 (the "Indenture") by and between the Company and
<PAGE>
 
the Trustee.  The terms of this Note include those stated in the Indenture and
those made part of the Indenture by reference to the Trust Indenture Act of 1939
(15 U.S. Code (S)(S) 77aaa-77bbbb) as in effect on the date of the Indenture.
This Note is subject to all such terms, and the Holder of this Note is referred
to the Indenture and said Trust Indenture Act for a statement of them.  All
capitalized terms in this Note, unless otherwise defined, have the meanings
assigned to them by the Indenture.

          The Notes are general unsecured obligations of the Company limited to
up to $200,000,000 aggregate principal amount.  The Indenture imposes certain
restrictions on, among other things, the incurrence of indebtedness, the
incurrence of liens and the issuance of preferred stock by the Company and its
subsidiaries, mergers and sale of assets, the payments of dividends on, or the
repurchase of, capital stock of the Company and its subsidiaries, certain other
restricted payments by the Company and its subsidiaries, certain transactions
with, and investments in, its affiliates, certain sale and lease-back
transactions and a provision regarding change-of-control transactions.  The
restrictions are subject to a number of important qualifications and exceptions.

5.   SUBORDINATION.

          The Indebtedness represented by the Notes is, to the extent and in the
manner provided in the Indenture, subordinated in right of payment to the prior
indefeasible payment and satisfaction in full in cash of all existing and future
Senior Indebtedness as defined in the Indenture, and this Note is issued subject
to such provisions.  Each Holder of this Note, by accepting the same, (a) agrees
to and shall be bound by such provisions, (b) authorizes and directs the
Trustee, on behalf of such Holder, to take such action as may be necessary or
appropriate to effectuate the subordination as provided in the Indenture and (c)
appoints the Trustee attorney-in-fact of such Holder for such purpose; provided,
                                                                       -------- 
however, that the Indebtedness evidenced by this Note shall cease to be so
- -------                                                                   
subordinate and subject in right of payment upon any defeasance of this Note
referred to in Paragraph 18 below.

6.   OPTIONAL REDEMPTION.

          The Company may redeem the Notes, in whole or in part, at any time on
or after July 15, 2001 at the redemption prices set forth in Section 3.07 of the
Indenture, together, in  each case, with accrued and unpaid interest to the
redemption date.

          In addition, the Company may redeem Notes out of the Net Proceeds of
one or more Public Equity Offerings at the redemption price, in the amount and
under the terms set forth in the Indenture.
<PAGE>
 
 7.  NOTICE OF REDEMPTION.

          Notice of redemption will be mailed via first class mail at least 30
days but not more than 60 days prior to the redemption date to each Holder of
Notes to be redeemed at its registered address as it shall appear on the
register of the Notes maintained by the Registrar.  On and after any Redemption
Date, interest will cease to accrue on the Notes or portions thereof called for
redemption unless the Company shall fail to redeem any such Note.

8.   OFFERS TO PURCHASE.

          The Indenture requires that certain proceeds from Asset Sales be used,
subject to further limitations contained therein, to make an offer to purchase
certain amounts of Notes in accordance with the procedures set forth in the
Indenture.  The Company is also required to make an offer to purchase Notes upon
occurrence of a Change of Control in accordance with procedures set forth in the
Indenture.

9.   REGISTRATION RIGHTS.

          Pursuant to the Registration Rights Agreement by and between the
Company and CIBC Wood Gundy Securities Corp., as initial purchaser of the Notes,
the Company will be obligated to consummate an exchange offer pursuant to which
the Holder of this Note shall have the right to exchange this Note for Notes of
a separate series issued under the Indenture (or a trust indenture substantially
identical to the Indenture in accordance with the terms of the Registration
Rights Agreement) which have been registered under the Securities Act, in like
principal amount and having substantially identical terms as the Notes.  The
Holders shall be entitled to receive certain additional interest payments in the
event such exchange offer is not consummated and upon certain other conditions,
all pursuant to and in accordance with the terms of the Registration Rights
Agreement.

10.  DENOMINATIONS, TRANSFER, EXCHANGE.

          The Notes are in registered form without coupons in denominations of
$1,000 and integral multiples thereof.  A Holder may register the transfer or
exchange of Notes in accordance with the Indenture.  The Registrar may require a
Holder, among other things, to furnish appropriate endorsements and transfer
documents and to pay any taxes and fees required by law or permitted by the
Indenture.  The Registrar need not register the transfer of or exchange any Note
selected for redemption or register the transfer of or exchange any Note for a
period of 15 days before a selection of Notes to be redeemed or any Note after
it is called for redemption in whole or in part, except the unredeemed portion
of any Note being redeemed in part.
<PAGE>
 
11.  PERSONS DEEMED OWNERS.

          The registered Holder of this Note may be treated as the owner of it
for all purposes.

12.  UNCLAIMED MONEY.

          If money for the payment of principal, premium or interest on any Note
remains unclaimed for two years, the Trustee or Paying Agent will pay the money
back to the Company at its request.  After that, Holders entitled to money must
look to the Company for payment as general creditors unless an "abandoned
property" law designates another person.

13.  AMENDMENT, SUPPLEMENT AND WAIVER.

          Subject to certain exceptions, the Indenture or the Notes may be
modified, amended or supplemented by the Company, the Guarantors, if any, and
the Trustee with the consent of the Holders of at least a majority in principal
amount of the Notes then outstanding and any existing default or compliance with
any provision may be waived in a particular instance with the consent of the
Holders of a majority in principal amount of the Notes then outstanding.
Without the consent of Holders, the Company, the Guarantors, if any, and the
Trustee may amend the Indenture or the Notes or supplement the Indenture for
certain specified purposes including providing for uncertificated Notes in
addition to certificated Notes, and curing any ambiguity, defect or
inconsistency, or making any other change that does not materially and adversely
affect the rights of any Holder.

14.  SUCCESSOR ENTITY.

          When a successor corporation assumes all the obligations of its
predecessor under the Notes and the Indenture and immediately before and
thereafter no Default exists and certain other conditions are satisfied, the
predecessor corporation will be released from those obligations.

15.  DEFAULTS AND REMEDIES.

          Events of Default are set forth in the Indenture.  If an Event of
Default (other than an Event of Default pursuant to Section 6.01(6) or (7) of
the Indenture with respect to the Company) occurs and is continuing, the Trustee
by notice to the Company, or the Holders of not less than 25% in aggregate
principal amount of the Notes then outstanding by written notice to the Company
and the Trustee, may declare to be immediately due and payable the entire
principal amount of all the Notes then outstanding plus accrued but unpaid
interest to the date of acceleration and (i) such amounts shall become
immediately due and payable or (ii) if there are any amounts outstanding under
or in
<PAGE>
 
respect of the Credit Facility, such amounts shall become due and payable upon
the first to occur of an acceleration of amounts outstanding under or in respect
of the Credit Facility or five Business Days after receipt by the Company and
the Representative of notice of the acceleration of the Notes; provided,
                                                               -------- 
however, that after such acceleration but before judgment or decree based on
- -------                                                                     
such acceleration is obtained by the Trustee, the Holders of a majority in
aggregate principal amount of the outstanding Notes may rescind and annul such
acceleration and its consequences if all existing Events of Default, other than
the nonpayment of principal, premium or interest that has become due solely
because of the acceleration, have been cured or waived and if the rescission
would not conflict with any judgment or decree. No such rescission shall affect
any subsequent Default or impair any right consequent thereto.  In case an Event
of Default specified in Section 6.01(6) or (7) of the Indenture with respect to
the Company occurs, such principal amount, together with premium, if any, and
interest with respect to all of the Notes, shall be due and payable immediately
without any declaration or other act on the part of the Trustee or the Holders
of the Notes.  The Trustee may withhold from Holders notice of any continuing
default (except a default in payment of principal, premium, if any, or interest)
if it determines that withholding notice is in their interests.

16.  TRUSTEE DEALINGS WITH THE COMPANY.

          The Trustee under the Indenture, in its individual or any other
capacity, may make loans to, accept deposits from, and perform services for the
Company, any Guarantor or their Affiliates, and may otherwise deal with the
Company, any Guarantor or their Affiliates, as if it were not Trustee.

17.  NO RECOURSE AGAINST OTHERS.

          As more fully described in the Indenture, a director, officer,
employee, partner, affiliate, beneficiary or stockholder, as such, of the
Company or  any Guarantor shall not have any liability for any obligations of
the Company or any Guarantor under the Notes or the Indenture or for any claim
based on, in respect or by reason of, such obligations or their creation.  The
Holder of this Note by accepting this Note waives and releases all such
liability.  The waiver and release are part of the consideration for the
issuance of this Note.

18.  DEFEASANCE AND COVENANT DEFEASANCE.

          The Indenture contains provisions for defeasance of the entire
indebtedness on this Note and for defeasance of certain covenants in the
Indenture upon compliance by the Company with certain conditions set forth in
the Indenture.
<PAGE>
 
19.  ABBREVIATIONS.

          Customary abbreviations may be used in the name of a Holder of a Note
or an assignee, such as:  TEN COM (= tenants in common), TEN ENT (= tenants by
the entireties), JT TEN (= joint tenants with right of survivorship and not as
tenants in common), CUST (= Custodian), and U/G/M/A (= Uniform Gifts to Minors
Act).

20.  CUSIP NUMBERS.

          Pursuant to a recommendation promulgated by the Committee on Uniform
Note Identification Procedures, the Company has caused CUSIP numbers to be
printed on the Notes and has directed the Trustee to use CUSIP numbers in
notices of redemption as a convenience to Holders of the Notes.  No
representation is made as to the accuracy of such numbers either as printed on
the Notes or as contained in any notice of redemption and reliance may be placed
only on the other identification numbers placed thereon.

21.  GOVERNING LAW.

          THIS INDENTURE AND THE NOTES SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, AS APPLIED TO CONTRACTS MADE
AND PERFORMED WITHIN THE STATE OF NEW YORK, WITHOUT REGARD TO PRINCIPLES OF
CONFLICTS OF LAW.  EACH OF THE PARTIES HERETO AGREES TO SUBMIT TO THE
JURISDICTION OF THE COURTS OF THE STATE OF NEW YORK IN ANY ACTION OR PROCEEDING
ARISING OUT OF OR RELATING TO THIS INDENTURE OR THE NOTES.

          THE COMPANY WILL FURNISH TO ANY HOLDER OF A NOTE UPON WRITTEN REQUEST
AND WITHOUT CHARGE A COPY OF THE INDENTURE.  REQUESTS MAY BE MADE TO:  PIERCE
LEAHY CORP., 631 Park Avenue, King of Prussia, Pennsylvania 19406, Attention:
Chief Financial Officer.

22.  AUTHENTICATION

          This Note shall not be valid until the Trustee manually signs the
Certificate of Authentication on the face of this Note.
<PAGE>
 
                                  ASSIGNMENT


I or we assign and transfer this Note to:

            (Insert assignee's social security or tax I.D. number)

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________
(Print or type name, address and zip code of assignee)

and irrevocably appoint:

________________________________________________________________________________

________________________________________________________________________________

Agent to transfer this Note on the books of the Company.  The Agent may
substitute another to act for him.

                                  [Check One]
                                   --------- 

[  ] (a)  this Note is being transferred in compliance with the exemption from
          registration under the Securities Act provided by Rule 144A
          thereunder.

                                       or
                                       --

[  ] (b)  this Note is being transferred other than in accordance with (a) above
          and documents are being furnished which comply with the conditions of
          transfer set forth in this Note and the Indenture.

If none of the foregoing boxes is checked, the Trustee or Registrar shall not be
obligated to register this Note in the name of any person other than the Holder
hereof unless and until the conditions to any such transfer of registration set
forth herein and in Section 2.15 of the Indenture shall have been satisfied.

Date: ____________________          Your Signature:  __________________

                                    ___________________________________
                                    (Sign exactly as your name
                                    appears on the face of this Note)


     Signature Guarantee:           ___________________________________
<PAGE>
 
                                      -2-

             TO BE COMPLETED BY PURCHASER IF (a) ABOVE IS CHECKED

          The undersigned represents and warrants that it is purchasing this
Note for its own account or an account with respect to which it exercises sole
investment discretion and that it and any such account is a "qualified
institutional buyer" within the meaning of Rule 144A under the Securities Act
and is aware that the sale to it is being made in reliance on Rule 144A and
acknowledges that it has received such information regarding the Company as the
undersigned has requested pursuant to Rule 144A or has determined not to request
such information and that it is aware that the transferor is relying upon the
undersigned's foregoing representations in order to claim the exemption from
registration provided by Rule 144A.


Dated: ____________________           ______________________________
                                      NOTICE:  To be executed by
                                               an executive officer
<PAGE>
 
                      OPTION OF HOLDER TO ELECT PURCHASE


          If you want to elect to have all or any part of this Note purchased by
the Company pursuant to Section 4.10 or Section 4.19 of the Indenture, check the
appropriate box:

     [_]    Section 4.10          [_]    Section 4.19


          If you want to have only part of the Note purchased by the Company
pursuant to Section 4.10 or Section 4.19 of the Indenture, state the amount you
elect to have purchased:


$____________________
 (multiple of $1,000)

Date: _______________


               Your Signature: __________________________________________
 
               (Sign exactly as your name appears on the face
               of this Note)



________________________
Signature Guaranteed
