<PAGE> 1

             UNCONDITIONAL GUARANTY OF PAYMENT AND PERFORMANCE
             -------------------------------------------------


      FOR AND IN CONSIDERATION OF the sum of Ten and No/100 Dollars ($10.00)
and other good and valuable consideration paid or delivered to the
undersigned STORAGE TRUST REALTY, a Maryland real estate investment trust
(hereinafter referred to as "Guarantor"), the receipt and sufficiency whereof
are hereby acknowledged by Guarantor, and for the purpose of seeking to
induce BANKBOSTON, N. A. A national banking association (hereinafter
referred to as "BKB"), BANK OF AMERICA NATIONAL TRUST AND SAVINGS
ASSOCIATION, A national banking association (hereinafter referred to as
"BOA"; BKB and BOA are hereinafter referred to collectively as "Lender",
which term shall also include each other Bank which may now or hereafter
become party to the "Credit Agreement" (as hereinafter defined) and shall
also include any such individual Bank acting as agent for all of the Banks),
to extend credit or otherwise provide financial accommodations to STORAGE
TRUST PROPERTIES, L.P., A Delaware limited partnership (hereinafter
referred to as "Borrower"), which extension of credit and provision of
financial accommodations will be to the direct interest, advantage and
benefit of Guarantor, Guarantor does hereby absolutely, unconditionally and
irrevocably guarantee to Lender:

      (a)   the full and prompt payment when due, whether by acceleration or
otherwise, either before or after maturity thereof, of that certain Note of
even date herewith made by Borrower to the order of BKB in the principal face
amount of One Hundred Twenty-Five Million and No/100 Dollars
($125,000,000.00) and that certain Swing Loan Note of even date herewith made
by Borrower to the order of BKB in the principal face amount of Ten Million
and No/100 Dollars ($10,000,000.00) (hereinafter referred to collectively as
the "BKB Note") together with interest as provided in the BKB Note, together
with any replacements, supplements, renewals, modifications, consolidations,
restatements and extensions thereof; and

      (b)   the full and prompt payment when due, whether by acceleration or
otherwise, either before or after maturity thereof, of that certain Note of
even date herewith made by Borrower to the order of BOA in the principal face
amount of Twenty-Five Million and No/100 Dollars ($25,000,000.00)
(hereinafter referred to as the "BOA Note") together with interest as
provided in the BOA Note, together with any replacements, supplements,
renewals, modifications, consolidations, restatements and extensions thereof;
and

      (c)   the full and prompt payment when due, whether by acceleration or
otherwise, either before or after maturity thereof, of each other note as may
be issued under that certain Revolving Credit Agreement dated of even date
herewith (hereinafter referred to as the "Credit Agreement") among Borrower,
BKB, for itself and as agent, and BOA, together with interest as provided in
each such note, together with any replacements, supplements, renewals,
modifications, consolidations, restatements and extensions thereof (the BKB
Note, the BOA Note and each of the notes described in this subparagraph (c)
is hereinafter referred to collectively as the "Note"); and

      (d)   the full and prompt payment and performance of all obligations of
Borrower to Lender under the terms of the Credit Agreement, together with any
replacements, supplements, renewals, modifications, consolidations,
restatements and extensions thereof; and

      (e)   the full and prompt payment and performance of any and all other
obligations of Borrower to Lender under any other agreements, documents or
instruments now or hereafter evidencing, securing or otherwise relating to
the indebtedness evidenced by the Note or the Credit Agreement (the Note, the
Credit Agreement and said other agreements, documents and instruments, are
hereinafter collectively referred to as the "Loan Documents" and individually


<PAGE> 2

referred to as a "Loan Document").  All terms used herein and not otherwise
defined herein shall have the meanings set forth in the Credit Agreement.

      1.    Agreement to Pay and Perform; Costs of Collection.  Guarantor does
            -------------------------------------------------
hereby agree that if the Note is not paid by Borrower in accordance with its
terms, or if any and all sums which are now or may hereafter become due from
Borrower to Lender under the Loan Documents are not paid by Borrower in
accordance with their terms, or if any and all other obligations of Borrower
to Lender under the Note and the Loan Documents are not performed by Borrower
in accordance with their terms, Guarantor will immediately make such payments
and perform such obligations.  Guarantor further agrees to pay Lender on
demand all reasonable costs and expenses (including court costs and
reasonable attorneys' fees and disbursements) paid or incurred by Lender in
endeavoring to collect the indebtedness guaranteed hereby, to enforce any of
the other obligations of Borrower guaranteed hereby, or any portion thereof,
or to enforce this Guaranty, and until paid to Lender, such sums shall bear
interest at the default rate set forth in the Credit Agreement unless
collection from Guarantor of interest at such rate would be contrary to
applicable law, in which event such sums shall bear interest at the highest
rate which may be collected from Guarantor under applicable law.

      2.    Reinstatement of Refunded Payments.  If, for any reason, any
            ----------------------------------
payment to Lender of any of the obligations guaranteed hereunder is required
to be refunded by Lender to Borrower, or paid or turned over to any other
person, including, without limitation, by reason of the operation of
bankruptcy, reorganization, receivership or insolvency laws or similar laws
of general application relating to creditors' rights and remedies now or
hereafter enacted, Guarantor agrees to pay the amount so required to be
refunded, paid or turned over (the "Turnover Payment"), the obligations of
Guarantor shall not be treated as having been discharged by the original
payment to Lender giving rise to the Turnover Payment, and this Guaranty
shall be treated as having remained in full force and effect for any such
Turnover Payment so made by Lender, as well as for any amounts not
theretofore paid to Lender on account of such obligations.

      3.    Rights of Lender to Deal with Collateral, Borrower and Other
            ------------------------------------------------------------
Persons.  Guarantor hereby consents and agrees that Lender may at any time,
-------
and from time to time, without thereby releasing Guarantor from any liability
hereunder and without notice to or further consent from Guarantor, either
with or without consideration:  release or surrender any lien or other
security of any kind or nature whatsoever held by it or by any person, firm
or corporation on its behalf or for its account, securing any indebtedness or
liability hereby guaranteed; substitute for any collateral so held by it,
other collateral of like kind, or of any kind; modify the terms of the Note
or the Loan Documents; extend or renew the Note for any period; grant
releases, compromises and indulgences with respect to the Note or the Loan
Documents and to any persons or entities now or hereafter liable thereunder
or hereunder; release any other Guarantor, surety, endorser or accommodation
party of the Note or any other Loan Documents; or take or fail to take any
action of any type whatsoever.  No such action which Lender shall take or
fail to take in connection with the Note or the Loan Documents, or any of
them, or any security for the payment of the indebtedness of Borrower to
Lender or for the performance of any obligations or undertakings of Borrower,
nor any course of dealing with Borrower or any other person, shall release
Guarantor's obligations hereunder, affect this Guaranty in any way or afford
Guarantor any recourse against Lender.  The provisions of this Guaranty shall
extend and be applicable to all replacements, supplements, renewals,
amendments, extensions, consolidations, restatements and modifications of the
Note and the Loan Documents, and any and all references herein to the Note
and the Loan Documents shall be deemed to include any such replacements,
supplements, renewals, extensions, amendments, consolidations, restatements
or modifications thereof.  Without limiting the generality of the foregoing,
Guarantor acknowledges the terms of Section 18.3 of the Credit Agreement and
agrees

                                    -2-
<PAGE> 3

that this Guaranty shall extend and be applicable to each new or replacement
note delivered by Borrower pursuant thereto without notice to or further
consent from Guarantor.

      4.    No Contest with Lender; Subordination.  So long as any obligation
            -------------------------------------
hereby guaranteed remains unpaid or undischarged, Guarantor will not, by
paying any sum recoverable hereunder (whether or not demanded by Lender) or
by any means or on any other ground, claim any set-off or counterclaim
against Borrower in respect of any liability of Guarantor to Borrower or, in
proceedings under federal bankruptcy law or insolvency proceedings of any
nature, prove in competition with Lender in respect of any payment hereunder
or be entitled to have the benefit of any counterclaim or proof of claim or
dividend or payment by or on behalf of Borrower or the benefit of any other
security for any obligation hereby guaranteed which, now or hereafter, Lender
may hold or in which it may have any share. Guarantor hereby expressly waives
any right of contribution from or indemnity against Borrower, whether at law
or in equity, arising from any payments made by Guarantor pursuant to the
terms of this Guaranty, and Guarantor acknowledges that Guarantor has no
right whatsoever to proceed against Borrower for reimbursement of any such
payments.  In connection with the foregoing, Guarantor expressly waives any
and all rights of subrogation to Lender against Borrower, and Guarantor
hereby waives any rights to enforce any remedy which Lender may have against
Borrower and any rights to participate in any collateral for Borrower's
obligations under the Loan Documents.  Guarantor hereby subordinates any and
all indebtedness of Borrower now or hereafter owed to Guarantor to all
indebtedness of Borrower to Lender, and agrees with Lender that (a) Guarantor
shall not demand or accept any payment from Borrower on account of such
indebtedness, (b) Guarantor shall not claim any offset or other reduction of
Guarantor's obligations hereunder because of any such indebtedness, and (c)
Guarantor shall not take any action to obtain any interest in any of the
security described in and encumbered by the Loan Documents because of any
such indebtedness; provided, however, that, if Lender so requests, such
indebtedness shall be collected, enforced and received by Guarantor as
trustee for Lender and be paid over to Lender on account of the indebtedness
of Borrower to Lender, but without reducing or affecting in any manner the
liability of Guarantor under the other provisions of this Guaranty except to
the extent the principal amount of such outstanding indebtedness shall have
been reduced by such payment.

      5.    Waiver of Defenses.  Guarantor hereby agrees that its obligations
            ------------------
hereunder shall not be affected or impaired by, and hereby waives and agrees
not to assert or take advantage of any defense based on:

            (a)   any statute of limitations in any action hereunder or for
the collection of the Note or for the payment or performance of any
obligation hereby guaranteed;

            (b)   the incapacity or lack of authority of Borrower or any other
person or entity, or the failure of Lender to file or enforce a claim against
the estate (either in administration, bankruptcy or in any other proceeding)
of Borrower, Guarantor, any Additional Guarantor or any other person or
entity;

            (c)   the dissolution or termination of existence of Borrower,
Guarantor or any Additional Guarantor;

            (d)   the voluntary or involuntary liquidation, sale or other
disposition of all or substantially all of the assets of Borrower;

            (e)   the voluntary or involuntary receivership, insolvency,
bankruptcy, assignment for the benefit of creditors, reorganization,
assignment, composition, or readjustment

                                    -3-
<PAGE> 4

of, or any similar proceeding affecting, Borrower, Guarantor or any
Additional Guarantor, or any of Borrower's, Guarantor's or any Additional
Guarantor's properties or assets;

            (f)   the damage, destruction, condemnation, foreclosure or
surrender of all or any part of the Real Estate or any of the improvements
located thereon;

            (g)   the failure of Lender to give notice of the existence,
creation or incurring of any new or additional indebtedness or obligation or
of any action or nonaction on the part of any other person whomsoever in
connection with any obligation hereby guaranteed;

            (h)   any failure or delay of Lender to commence an action against
Borrower, to assert or enforce any remedies against Borrower under the Note
or the Loan Documents, or to realize upon any security;

            (i)   any failure of any duty on the part of Lender to disclose
to Guarantor any facts it may now or hereafter know regarding Borrower, the
Real Estate or any of the improvements located thereon, whether such facts
materially increase the risk to Guarantor or not;

            (j)   failure to accept or give notice of acceptance of this
Guaranty by Lender;

            (k)   failure to make or give notice of presentment and demand for
payment of any of the indebtedness or performance of any of the obligations
hereby guaranteed;

            (l)   failure to make or give protest and notice of dishonor or of
default to Guarantor or to any other party with respect to the indebtedness
or performance of obligations hereby guaranteed;

            (m)   except as otherwise specifically provided in this Guaranty,
any and all other notices whatsoever to which Guarantor might otherwise be
entitled;

            (n)   any lack of diligence by Lender in collection, protection or
realization upon any collateral securing the payment of the indebtedness or
performance of obligations hereby guaranteed;

            (o)   the invalidity or unenforceability of the Note or any of
the Loan Documents;

            (p)   the compromise, settlement, release or termination of any or
all of the obligations of Borrower or any Additional Guarantor under the Note
or the Loan Documents;

            (q)   any transfer by Borrower of all or any part of the security
encumbered by the Loan Documents;

            (r)   the failure of Lender to perfect any security or to extend
or renew the perfection of any security; or

            (s)   to the fullest extent permitted by law, any other legal,
equitable or surety defenses whatsoever to which Guarantor might otherwise be
entitled (other than the defense of payment), it being the intention that the
obligations of Guarantor hereunder are absolute, unconditional and
irrevocable.

      6.    Guaranty of Payment and Performance and Not of Collection. This
            ---------------------------------------------------------
is a Guaranty of payment and performance and not of collection.  The
liability of Guarantor under this Guaranty shall be primary, direct and
immediate and not conditional or contingent upon the pursuit of any

                                    -4-
<PAGE> 5

remedies against Borrower or any other person, nor against securities or
liens available to Lender, its successors, successors in title, endorsees or
assigns.  Guarantor hereby waives any right to require that an action be
brought against Borrower or any other person or to require that resort be had
to any security or to any balance of any deposit account or credit on the
books of Lender in favor of Borrower or any other person.

      7.    Rights and Remedies of Lender.  In the event of a default under
            -----------------------------
the Note or the Loan Documents, or any of them, Lender shall have the right
to enforce its rights, powers and remedies thereunder or hereunder or under
any other agreement, document or instrument now or hereafter evidencing,
securing or otherwise relating to the indebtedness evidenced by the Note or
secured by the Loan Documents, in any order, and all rights, powers and
remedies available to Lender in such event shall be nonexclusive and
cumulative of all other rights, powers and remedies provided thereunder or
hereunder or by law or in equity.  Accordingly, Guarantor hereby authorizes
and empowers Lender upon the occurrence of any event of default under the
Note or the Loan Documents, at its sole discretion, and without notice to
Guarantor, to exercise any right or remedy which Lender may have, including,
but not limited to, judicial foreclosure, exercise of rights of power of
sale, acceptance of a deed or assignment in lieu of foreclosure, appointment
of a receiver to collect rents and profits, exercise of remedies against
personal property, or enforcement of any assignment of leases, as to any
security, whether real, personal or intangible.  At any public or private
sale of any security or collateral for any indebtedness or any part thereof
guaranteed hereby, whether by foreclosure or otherwise, Lender may, in its
discretion, purchase all or any part of such security or collateral so sold
or offered for sale for its own account and may apply against the amount bid
therefor all or any part of the balance due it pursuant to the terms of the
Note or any other Loan Document without prejudice to Lender's remedies
hereunder against Guarantor for deficiencies.  If the indebtedness guaranteed
hereby is partially paid by reason of the election of Lender to pursue any of
the remedies available to Lender, or if such indebtedness is otherwise
partially paid, this Guaranty shall nevertheless remain in full force and
effect, and Guarantor shall remain liable for the entire balance of the
indebtedness guaranteed hereby even though any rights which Guarantor may
have against Borrower may be destroyed or diminished by the exercise of any
such remedy.

      8.    Application of Payments.  Guarantor hereby authorizes Lender,
            -----------------------
without notice to Guarantor, to apply all payments and credits received from
Borrower or from Guarantor or any other Person or realized from any security
in such manner and in such priority as Lender in its sole judgment shall see
fit to the indebtedness, obligation and undertakings which are the subject of
this Guaranty.

      9.    Business Failure, Bankruptcy or Insolvency.  In the event of the
            ------------------------------------------
business failure of Guarantor or if there shall be pending any bankruptcy or
insolvency case or proceeding with respect to Guarantor under federal
bankruptcy law or any other applicable law or in connection with the
insolvency of Guarantor, or if a liquidator, receiver, or trustee shall have
been appointed for Guarantor or Guarantor's properties or assets, Lender may
file such proofs of claim and other papers or documents as may be necessary
or advisable in order to have the claims of Lender allowed in any proceedings
relative to Guarantor, or any of Guarantor's properties or assets, and,
irrespective of whether the indebtedness or other obligations of Borrower
guaranteed hereby shall then be due and payable, by declaration or otherwise,
Lender shall be entitled and empowered to file and prove a claim for the
whole amount of any sums or sums owing with respect to the indebtedness or
other obligations of Borrower guaranteed hereby, and to collect and receive
any moneys or other property payable or deliverable on any such claim.
Guarantor covenants and agrees that upon the commencement of a voluntary or
involuntary bankruptcy proceeding by or against Borrower or any Additional
Guarantor, Guarantor shall not seek a supplemental stay or otherwise pursuant
to 11 U.S.C. '105 or any other provision of the Bankruptcy Reform Act of

                                    -5-
<PAGE> 6

1978, as amended, or any other debtor relief law (whether statutory, common
law, case law, or otherwise) of any jurisdiction whatsoever, now or hereafter
in effect, which may be or become applicable, to stay, interdict, condition,
reduce or inhibit the ability of Lender to enforce any rights of Lender
against Guarantor by virtue of this Guaranty or otherwise.

      10.   Financial Statements and Other Information.  Guarantor hereby
            ------------------------------------------
represents and warrants to Lender that all financial statements of Guarantor
heretofore delivered by Guarantor to Lender are true and correct in all
material respects, have been prepared in accordance with generally accepted
accounting principles consistently applied, and fairly present the financial
condition of Guarantor as at the close of business on the date thereof and
the results of operations for the period then ended; that no material adverse
change has occurred in the assets, liabilities, financial condition or
business of Guarantor as shown or reflected therein since the date thereof;
and that Guarantor has no liabilities or known contingent liabilities
involving material amounts which are not reflected in such financial
statements or referred to in the notes thereto other than Guarantor's
obligations under this Guaranty.  Guarantor hereby agrees that until all
indebtedness guaranteed hereby has been completely repaid, all obligations
and undertakings of Borrower under, by reason of, or pursuant to the Note and
the Loan Documents have been completely performed and Lender has no further
obligation to make Loans to Borrower pursuant to the Credit Agreement,
Guarantor will deliver to Lender:

            (a)   as soon as practicable and in any event within 90 days after
the end of each fiscal year of Guarantor, the audited consolidated balance
sheet of Guarantor and its Subsidiaries as of the end of such year, and the
related audited consolidated statement of operations and statement of cash
flows for such year, each setting forth in comparative form the figures for
the previous fiscal year and all such statements to be in reasonable detail,
prepared in accordance with generally accepted accounting principles, and
accompanied by an auditor's report prepared without qualification by Ernst &
Young or by another national accounting firm approved by Agent, the Form 10K
filed with the SEC (unless the SEC has approved an extension, in which event
the Guarantor will deliver to each Lender a copy of the Form 10K
simultaneously with delivery to the SEC).  At any time that the Agent has
reasonable grounds to request the same (including, without limitation, at any
time that the Compliance Certificate indicates that the Guarantor is at or
near the minimum compliance with the financial covenants in this Guaranty),
the Agent may require that such report be accompanied by a written statement
from such accountants to the effect that they have read a copy of this
Guaranty and the Credit Agreement, and that, in making the examination
necessary to said certification, they have obtained no knowledge of any
Default or Event of Default under this Guaranty, or, if such accountants
shall have obtained knowledge of any then existing Default or Event of
Default they shall disclose in such statement any such Default or Event of
Default;

            (b)   as soon as practicable and in any event within 60 days after
the end of each of the first three fiscal quarters of Guarantor, copies of
the unaudited consolidated balance sheet of Guarantor and its Subsidiaries as
of the end of such quarter, and the related unaudited consolidated statement
of operations and statement of cash flows for the portion of Guarantor's
fiscal year then elapsed, all in reasonable detail and prepared in accordance
with generally accepted accounting principles (which may be provided by
inclusion in the Form 10-Q of the Guarantor for such period provided pursuant
to subsection (c) below), together with a certification by the principal
financial or accounting officer of Guarantor that the information contained
in such financial statements fairly presents the financial position of
Guarantor and its Subsidiaries on the date thereof (subject to year end
adjustment);

            (c)   contemporaneously with the delivery of the financial
statements referred to in clause (a) above, a statement of all contingent
liabilities of Guarantor which are not reflected in

                                    -6-
<PAGE> 7

such financial statements or referred to in the notes thereto (including,
without limitation, all guarantees, endorsements and other contingent
obligations in respect of indebtedness of others, and obligations to
reimburse the issuer in respect of any letters of credit), and a statement of
projected cash flows of Guarantor for the current fiscal year, all in
reasonable detail and certified by the principal financial or accounting
officer of Guarantor;

            (d)   contemporaneously with the filing or mailing thereof, copies
of all material of a financial nature filed with the SEC or sent to the
shareholders of Guarantor;

            (e)   as soon as practicable, but in any event not later than 60
days after the end of each fiscal quarter of the Guarantor (including the
fourth fiscal quarter in each year), copies of Form 10Q filed with the SEC
(unless the SEC has approved an extension in which event the Guarantor will
deliver such copies of the Form 10Q to each of Lender simultaneously with
delivery to the SEC);

            (f)   promptly after they are filed with the Internal Revenue
Service, copies of all annual federal income tax returns and amendments
thereto of Guarantor;

            (g)   not later than 60 days after the end of each fiscal quarter
of Guarantor (including the fourth fiscal quarter in each year), a statement,
certified as true and correct by the principal financial or accounting
officer of Guarantor, of all Indebtedness of Guarantor as of the end of such
fiscal quarter, which statement shall include the original principal amount
of such Indebtedness and the current amount outstanding, the holder thereof,
the maturity date and any extension options, the interest rate, the
collateral provided for such Indebtedness and whether such Indebtedness is
recourse or non-recourse;

            (h)   concurrently with the delivery of the financial statements
described in subsections (b) and (e) above, a certificate signed by the
President or Chief Financial Officer of Guarantor to the effect that, having
read this Guaranty, and that based upon an examination which they deem
sufficient to enable them to make an informed statement, there does not exist
any Default or Event of Default, or if such Default or Event of Default has
occurred, specifying the facts with respect thereto;

            (i)   not later than five (5) Business Days after the Guarantor
receives notice of the same from a Rating Agency or otherwise learns of the
same, notice of the issuance of any change in the rating by such Rating
Agency in respect of any debt of the Guarantor (including any change in an
Implied Rating), together with the details thereof, and of any announcement
by a Rating Agency that any such rating is "under review" or that any such
rating has been placed on a watch list or that any similar action has been
taken by a Rating Agency (collectively a "Rating Notice");

            (j)   promptly upon becoming aware thereof, written notice from
Guarantor of any event or condition which might have a material adverse
effect on the business, operations, assets, condition (financial or
otherwise) or prospects of Guarantor or the ability of Guarantor to perform
under this Guaranty (including but not limited to, litigation commenced or
threatened in writing against Guarantor, judgments rendered against
Guarantor, liens filed against any property of Guarantor, defaults claimed
under indebtedness for borrowed money for which Guarantor is primarily or
secondarily liable, or bankruptcy, insolvency or trustee or receivership
proceedings commenced against Guarantor), such notice to specify the nature
and the period of existence of such event or condition, the anticipated
effect thereof, and what action Guarantor is taking or proposes to take with
respect thereto; and

                                    -7-
<PAGE> 8

            (k)   with reasonable promptness, such other information
respecting the business, operations, assets, liabilities and financial
condition of Guarantor as Lender may from time to time reasonably request.

Notwithstanding anything herein to the contrary, Guarantor shall not be
required to deliver any statements or reports described in this Paragraph 10
to the extent the same are delivered to the Banks by the Borrower as and when
required by this Guaranty.  Guarantor will permit any officer designated by
Lender, at Guarantor's expense, to visit and inspect any of the properties of
Guarantor, to examine the records and books of account of Guarantor (and to
make copies thereof and extracts therefrom) and to discuss the affairs,
finances and accounts of Guarantor with, and to be advised as to the same by,
its officers, all at such reasonable times and intervals Lender may
reasonably request.

      11.   Covenants of Guarantor.  Guarantor hereby covenants and agrees
            ----------------------
with Lender that until all indebtedness guaranteed hereby has been completely
repaid and all obligations and undertakings of Borrower under, by reason of,
or pursuant to the Note and the Loan Documents have been completely performed
and Lender has no further obligations to make Loans to Borrower pursuant to
the Credit Agreement:

            (a)   Guarantor will, and will cause each of its Subsidiaries to,
do or cause to be done all things necessary to preserve and keep in full
force and effect its corporate or legal existence, material rights and
franchises, as applicable, to effect and maintain its foreign qualifications,
licensing, domestication or authorization, and to comply with all applicable
laws and regulations (including, without limitation, environmental laws);

            (b)   Guarantor will have as its sole business purpose being the
sole general partner of the Borrower and will own no assets other than its
general partnership interest in the Borrower, Short-term Investments, its
ownership of the stock of the corporate general partners of Subsidiaries of
the Borrower and other assets (such as prepaid insurance) reasonably
necessary for the operation of Guarantor's business in the ordinary course of
business consistent with the terms of this Guaranty and the other Loan
Documents;

            (c)   Guarantor will, and will cause each of its Subsidiaries to,
duly pay and discharge, before the same shall become in arrears, all taxes,
assessments and other governmental charges imposed upon it and its
properties, sales or activities, or upon the income or profits therefrom, as
well as claims for labor, material, or supplies which if unpaid might become
a lien or charge on any of its property; provided that any such tax,
assessment, charge or claim need not be paid if the validity or amount
thereof shall currently be contested in good faith by appropriate proceedings
and if Guarantor or such Subsidiary shall have set aside on its books
adequate reserves with respect thereto; and provided further that Guarantor
or such Subsidiary shall pay all such taxes, assessments, charges and claims
forthwith upon the commencement of proceedings to foreclose any lien that may
have attached as security therefor;

            (d)   Guarantor will, and will cause each of its Subsidiaries to,
maintain and keep the properties used or deemed by it to be useful in its
business in first-class repair, working order and condition, and make or
cause to be made all necessary and proper repairs thereto and replacements
thereof;

            (e)   Guarantor will, and will cause each of its Subsidiaries to,
maintain with financially sound and reputable insurers, insurance with
respect to its properties and business against such casualties and
contingencies and in such types and amounts as shall be in accordance with
sound business practices for companies in similar business similarly
situated;

                                    -8-
<PAGE> 9

            (f)   Guarantor will keep, and will cause each of its Subsidiaries
to keep, complete, proper and accurate records and books of account in which
full, true and correct entries will be made in accordance with generally
accepted accounting principles consistent with the preparation of the
financial statements heretofore delivered to Lender and will maintain
adequate accounts and reserves for all taxes (including income taxes), all
depreciation, depletion, and amortization of its properties and the
properties of its Subsidiaries, all other contingencies, and all other proper
reserves;

            (g)   Guarantor will not create, incur, assume, guarantee or be or
remain liable, contingently or otherwise, with respect to any Indebtedness
other than:

                  (i)   Indebtedness to Lender arising under any of the Note,
      the Loan Documents and this Guaranty;

                  (ii)  current liabilities of Guarantor incurred in the
      ordinary course of business but not incurred through the borrowing of
      money or the obtaining of credit except for credit on an open account
      basis customarily extended and in fact extended in connection with
      normal purchases of goods and services;

                  (iii) Indebtedness in respect of taxes, assessments and
      governmental charges to the extent that payment therefor shall not at the
      time be required to be made in accordance with the provisions of
      subparagraph (c) of this paragraph;

                  (iv)  Indebtedness in respect of judgments or awards that
      have been in force for less than the applicable period for taking an
      appeal so long as execution is not levied thereunder or in respect of
      which Guarantor shall at the time in good faith be prosecuting an appeal
      or proceedings for review and in respect of which a stay of execution
      shall have been obtained pending such appeal or review;

                  (v)   endorsements for collection, deposit or negotiation
      and warranties of products or services, in each case incurred in the
      ordinary course of business; and

                  (vi)  Indebtedness evidenced by the guaranty by the
      Guarantor of the obligations of the Borrower with respect to the senior
      notes of the Borrower issued as of January 20, 1997 in a principal
      amount of $100,000,000.00 pursuant to a Note Purchase Agreement dated as
      of January 20, 1997 among Borrower, Guarantor and certain other parties.

                                    -9-
<PAGE> 10

            (h)   Guarantor will not, and will not permit any of its
Subsidiaries to, create or incur or suffer to be created or incurred or to
exist any lien, encumbrance, mortgage, pledge, charge, restriction or other
security interest of any kind upon any of its property or assets of any
character whether now owned or hereafter acquired, or upon the income or
profits therefrom; or transfer any of such property or assets or the income
or profits therefrom for the purpose of subjecting the same to the payment of
Indebtedness or performance of any other obligation in priority of payment of
its general creditors; or acquire, or agree to have an option to acquire, any
property or assets upon conditional sale or other title retention or purchase
money security agreement, devise or arrangement; or suffer to exist for a
period of more than 30 days after the same shall have been incurred any
Indebtedness or claim or demand against it that if unpaid might by law or
upon bankruptcy or insolvency, or otherwise, be given any priority whatsoever
over its general creditors; or sell, assign, pledge or otherwise transfer any
accounts, contract rights, general intangibles, chattel paper or instruments,
with or without recourse, or incur or maintain any obligation to any holder
of Indebtedness of Guarantor or such Subsidiary which prohibits the creation
or maintenance of any lien securing the Obligations; provided that Guarantor
and any Subsidiary of Guarantor may create or incur or suffer to be created
or incurred or to exist:

                  (i)   liens in favor of Guarantor on all or part of the
      assets of Subsidiaries of Guarantor securing Indebtedness owing by
      Subsidiaries of Guarantor to Guarantor;

                  (ii)  liens to secure taxes, assessments and other
      governmental charges or claims for labor, material or supplies in
      respect of obligations not overdue;

                  (iii) liens with respect of judgments or awards, the
      Indebtedness with respect to which is permitted by subparagraph (g)(iv)
      of this paragraph;


                  (iv)  liens in favor of Lender; and

                  (v)   liens specifically permitted pursuant to Section 8.2
      of the Credit Agreement.

            (i)   Guarantor will not, and will not permit any of its
Subsidiaries to, become a party to any merger, consolidation or other
business combination, or agree to effect any asset acquisition, stock
acquisition or other acquisition, except (A) the merger or consolidation or
one or more of the Subsidiaries of Guarantor with and into Guarantor, or (B)
the merger or consolidation of two or more Subsidiaries of Guarantor;

            (j)   Guarantor will not, and will not permit any of its
Subsidiaries to, become a party to or agree to or affect any disposition of
assets, other than Distributions to its shareholders as permitted in this
Guaranty;

            (k)   Guarantor will not make or permit to be made, by voluntary
or involuntary means, any transfer or encumbrance of its interest in
Borrower, or any dilution of its interest in Borrower;

            (l)   Guarantor shall contribute or otherwise downstream to
Borrower any cash or other assets received by Guarantor from third parties
(including, without limitation, the proceeds from any Debt Offering or Equity
Offering);

            (m)   The Guarantor shall at all times comply with all
requirements of applicable laws and regulations necessary to maintain REIT
Status and shall operate its business as described in the Prospectus and in
compliance with the terms and conditions of this Guaranty and the other Loan
Documents;

                                    -10-
<PAGE> 11

            (n)   Guarantor will be self-directed and will not retain or
otherwise rely on any other Person for investment advisory services;

            (o)   Guarantor shall not pay any Distribution to the shareholders
of the Guarantor if such Distribution is in excess of the amount which, when
added to the amount of all other Distributions paid in the same fiscal
quarter and the preceding fiscal quarter will exceed (i) ninety percent (90%)
of its Funds from Operations for the two (2) consecutive fiscal quarters
ending prior to the quarter in which such Distribution is paid, or (ii) one
hundred percent (100%) of its Funds Available for Distribution for the two
(2) consecutive fiscal quarters ending prior to the quarter in which such
Distribution is paid.  The foregoing limitation on Distributions shall not
preclude the Guarantor from paying Distributions necessary to maintain its
REIT Status; and

            (p)   Guarantor will cooperate with Lender and execute such
further instruments and documents as Lender shall reasonably request to carry
out to their satisfaction the transactions contemplated by this Guaranty and
the other Loan Documents.

      12.   Security and Rights of Set-off.  Guarantor hereby grants to
            ------------------------------
Lender, as security for the full and prompt payment and performance of
Guarantor's obligations hereunder, a continuing lien on and security interest
in any and all securities or other property belonging to Guarantor now or
hereafter held by Lender and in any and all deposits (general or specific,
time or demand, provisional or final, regardless of currency, maturity, or
the branch of Lender where the deposits are held) now or hereafter held by
Lender and other sums credited by or due from Lender to Guarantor or subject
to withdrawal by Guarantor; and regardless of the adequacy of any collateral
or other means of obtaining repayment of such obligations, during the
continuance of any Event of Default under the Note or the Loan Documents,
Lender may at any time and without notice to Guarantor set-off and apply the
whole or any portion or portions of any or all such deposits and other sums
against amounts payable under this Guaranty, whether or not any other person
or persons could also withdraw money therefrom.  Any security now or
hereafter held by or for Guarantor and provided by Borrower, or by anyone on
Borrower's behalf, in respect of liabilities of Guarantor hereunder shall be
held in trust for Lender as security for the liabilities of Guarantor
hereunder.

      13.   Changes in Writing; No Revocation.  This Guaranty may not be
            ---------------------------------
changed orally, and no obligation of Guarantor can be released or waived by
Lender except by a writing signed by a duly authorized officer of Lender.
This Guaranty shall be irrevocable by Guarantor until all indebtedness
guaranteed hereby has been completely repaid and all obligations and
undertakings of Borrower under, by reason of, or pursuant to the Note and the
Loan Documents have been completely performed.

      14.   Notices.  All notices, demands or requests provided for or
            -------
permitted to be given pursuant to this Guaranty (hereinafter in this
paragraph referred to as "Notice") must be in writing and shall be deemed to
have been properly given or served by personal delivery or by sending same by
overnight courier or by depositing the same in the United States mail,
postpaid and registered or certified, return receipt requested, at the
addresses set forth below.  Each Notice shall be effective upon being
delivered personally or upon being sent by overnight courier or upon being
deposited in the United States Mail as aforesaid.  The time period in which a
response to any such Notice must be given or any action taken with respect
thereto, however, shall commence to run from the date of receipt if
personally delivered or sent by overnight courier or, if so deposited in the
United States Mail, the earlier of three (3) Business Days following such
deposit and the date of receipt as disclosed on the return receipt.
Rejection or other refusal to accept or the inability to deliver because of
changed address of which no Notice was given shall be deemed to be receipt of

                                    -11-
<PAGE> 12

the Notice sent.  By giving at least fifteen (15) days prior Notice thereof,
Guarantor or Lender shall have the right from time to time and at any time
during the term of this Guaranty to change their respective addresses and
each shall have the right to specify as its address any other address within
the United States of America.  For the purposes of this Guaranty:

      The address of Lender is:

            BankBoston, N.A.
            100 Federal Street
            Boston, Massachusetts 02110
            Attn:  Real Estate Division

      with a copy to:

            BankBoston, N.A.
            115 Perimeter Center Place, N.E.
            Suite 500
            Atlanta, Georgia 30346
            Attn:  Dan Stegemoeller

      and to:

            Bank of America National Trust and Savings Association
            231 South LaSalle Street
            12th Floor
            Chicago, Illinois  60697
            Attn: George W. Kirtland, Jr.

and a copy to each other Lender which may now or hereafter become a party to
the Credit Agreement at such address as may be designated by such Lender.

      The address of Guarantor is:

            Storage Trust Realty
            2407 Rangeline
            Columbia, Missouri  65202
            Attn:  Stephen M. Dulle

      15.   Governing Law.  GUARANTOR ACKNOWLEDGES AND AGREES THAT
            -------------
THIS GUARANTY AND THE OBLIGATIONS OF GUARANTOR HEREUNDER SHALL BE
GOVERNED BY AND INTERPRETED AND DETERMINED IN ACCORDANCE WITH THE
LAWS OF THE COMMONWEALTH OF MASSACHUSETTS (EXCLUDING THE LAWS
APPLICABLE TO CONFLICTS OR CHOICE OF LAW).

      16.   CONSENT TO JURISDICTION; WAIVERS.  GUARANTOR HEREBY
            --------------------------------
IRREVOCABLY AND UNCONDITIONALLY (A) SUBMITS TO PERSONAL
JURISDICTION IN THE COMMONWEALTH OF MASSACHUSETTS OVER ANY SUIT,
ACTION OR PROCEEDING ARISING OUT OF OR RELATING TO THIS GUARANTY,
AND (B) WAIVES ANY AND ALL PERSONAL RIGHTS UNDER THE LAWS OF ANY
STATE (I) TO THE RIGHT, IF ANY, TO TRIAL BY JURY, (II) TO OBJECT
TO JURISDICTION

                                    -12-
<PAGE> 13

WITHIN THE COMMONWEALTH OF MASSACHUSETTS OR VENUE IN ANY
PARTICULAR FORUM WITHIN THE COMMONWEALTH OF MASSACHUSETTS, AND
(III) TO THE RIGHT, IF ANY, TO CLAIM OR RECOVER ANY SPECIAL,
EXEMPLARY, PUNITIVE OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES OTHER
THAN ACTUAL DAMAGES.  GUARANTOR AGREES THAT, IN ADDITION TO ANY
METHODS OF SERVICE OF PROCESS PROVIDED FOR UNDER APPLICABLE LAW,
ALL SERVICE OF PROCESS IN ANY SUCH SUIT, ACTION OR PROCEEDING MAY
BE MADE BY CERTIFIED OR REGISTERED MAIL, RETURN RECEIPT REQUESTED,
DIRECTED TO GUARANTOR AT THE ADDRESS SET FORTH IN PARAGRAPH 14
ABOVE, AND SERVICE SO MADE SHALL BE COMPLETE FIVE (5) DAYS AFTER
THE SAME SHALL BE SO MAILED.  NOTHING CONTAINED HEREIN, HOWEVER,
SHALL PREVENT LENDER FROM BRINGING ANY SUIT, ACTION OR PROCEEDING
OR EXERCISING ANY RIGHTS AGAINST ANY SECURITY AND AGAINST
GUARANTOR PERSONALLY, AND AGAINST ANY PROPERTY OF GUARANTOR,
WITHIN ANY OTHER STATE.  INITIATING SUCH SUIT, ACTION OR
PROCEEDING OR TAKING SUCH ACTION IN ANY STATE SHALL IN NO EVENT
CONSTITUTE A WAIVER OF THE AGREEMENT CONTAINED HEREIN THAT THE
LAWS OF THE COMMONWEALTH OF MASSACHUSETTS SHALL GOVERN THE RIGHTS
AND OBLIGATIONS OF GUARANTOR AND LENDER HEREUNDER OR OF THE
SUBMISSION HEREIN MADE BY GUARANTOR TO PERSONAL JURISDICTION
WITHIN THE COMMONWEALTH OF MASSACHUSETTS.  GUARANTOR HEREBY WAIVES
ANY OBJECTION THAT IT MAY NOW OR HEREAFTER HAVE TO THE VENUE OF
ANY SUCH SUIT OR ANY SUCH COURT OR THAT SUCH SUIT IS BROUGHT IN AN
INCONVENIENT COURT.  GUARANTOR CERTIFIES THAT NO REPRESENTATIVE,
AGENT OR ATTORNEY OF ANY LENDER HAS REPRESENTED, EXPRESSLY OR
OTHERWISE, THAT SUCH LENDER WOULD NOT, IN THE EVENT OF LITIGATION,
SEEK TO ENFORCE THEIR FOREGOING WAIVERS AND ACKNOWLEDGES THAT
LENDER HAS BEEN INDUCED TO ENTER INTO THIS GUARANTY AND THE OTHER
LOAN DOCUMENTS TO WHICH THEY ARE PARTIES BY, AMONG OTHER THINGS,
THE WAIVERS AND CERTIFICATIONS CONTAINED IN THIS PARAGRAPH 16.
GUARANTOR ACKNOWLEDGES THAT IT HAS HAD AN OPPORTUNITY TO REVIEW
THIS PARAGRAPH 16 WITH ITS LEGAL COUNSEL AND THAT GUARANTOR AGREES
TO THE FOREGOING AS ITS FREE, KNOWING AND VOLUNTARY ACT.

      17.   Successors and Assigns.  The provisions of this Guaranty shall be
            ----------------------
binding upon Guarantor and its heirs, successors, successors in title, legal
representatives, and assigns, and shall inure to the benefit of Lender, its
successors, successors in title, legal representatives and assigns.

      18.   Assignment by Lender.  This Guaranty is assignable by Lender in
            --------------------
whole or in part in conjunction with any assignment of the Note or portions
thereof, and any assignment hereof or any transfer or assignment of the Note
or portions thereof by Lender shall operate to vest in any such assignee the
rights and powers, in whole or in part, as appropriate, herein conferred upon
and granted to Lender.

                                    -13-
<PAGE> 14

      19.   Severability.  If any term or provision of this Guaranty shall be
            ------------
determined to be illegal or unenforceable, all other terms and provisions
hereof shall nevertheless remain effective and shall be enforced to the
fullest extent permitted by law.

      20.   Disclosure.  Guarantor agrees that in addition to disclosures made
            ----------
in accordance with standard banking practices, any Lender may disclose
information obtained by such Lender pursuant to this Guaranty to assignees or
participants and potential assignees or participants hereunder.

      21.   No Unwritten Agreements.  THIS GUARANTY REPRESENTS THE FINAL
            -----------------------
AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY
EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS
OF THE PARTIES.  THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN
THE PARTIES.

      22.   Time of the Essence.  Time is of the essence with respect to each
            -------------------
and every covenant, agreement and obligation of Guarantor under this
Guaranty.

      23.   Ratification.  Guarantor does hereby restate, reaffirm and ratify
            ------------
each and every warranty and representation regarding Guarantor or its
Subsidiaries set forth in the Credit Agreement as if the same were more fully
set forth herein.

      24.   Limitation on Liability.  NO OBLIGATION OR LIABILITY
            -----------------------
WHATSOEVER OF THE GUARANTOR (WHETHER  AS GUARANTOR OR AS GENERAL
PARTNER OF THE BORROWER) WHICH MAY ARISE AT ANY TIME UNDER THIS
GUARANTY OR ANY OBLIGATION OR LIABILITY WHICH MAY BE INCURRED BY
IT PURSUANT TO ANY OTHER LOAN DOCUMENT SHALL BE PERSONALLY BINDING
UPON, NOR SHALL RESORT FOR THE ENFORCEMENT THEREOF BE HAD TO, THE
PRIVATE PROPERTY OF ANY OF THE GUARANTOR'S SHAREHOLDERS, TRUSTEES,
OFFICERS OR EMPLOYEES, REGARDLESS OF WHETHER SUCH OBLIGATION OR
LIABILITY IS IN THE NATURE OF CONTRACT, TORT OR OTHERWISE.
NOTHING HEREIN SHALL DIMINISH OR IMPAIR THE RIGHTS OF AGENT AND
THE BANKS TO PURSUE ANY REMEDY AGAINST ANY ASSETS OF THE
GUARANTOR.

      IN WITNESS WHEREOF, Guarantor has executed this Guaranty under seal as
of the 25th day of January, 1998.

                                      STORAGE TRUST REALTY,
                                      a Maryland real estate investment trust


                                      By:------------------------------
                                       Name:---------------------------


                                                     [SEAL]

                                    -14-