<PAGE>
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549
                            ------------------------

                                  FORM 10-K/A

                               (AMENDMENT NO. 1)

(MARK ONE)

<TABLE>
<C>        <S>
   /X/     ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
           SECURITIES EXCHANGE ACT OF 1934
</TABLE>

                  FOR THE FISCAL YEAR ENDED DECEMBER 31, 1999
                                       OR

<TABLE>
<C>        <S>
   / /     TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
           SECURITIES EXCHANGE ACT OF 1934
</TABLE>

                         COMMISSION FILE NUMBER 1-14307
                            ------------------------
                                GREAT LAKES REIT

             (Exact Name of Registrant as Specified in Its Charter)

<TABLE>
<S>                                            <C>
               MARYLAND                                     36-4238056
    (State or Other Jurisdiction of              (I.R.S. Employer Identification
    Incorporation or Organization)                           Number)
</TABLE>

                               823 COMMERCE DRIVE
                                   SUITE 300
                           OAK BROOK, ILLINOIS 60523
                                 (630) 368-2900
         (Address and telephone number of principal executive offices)

          Securities registered pursuant to Section 12(b) of the Act:

              COMMON SHARES OF BENEFICIAL INTEREST, $.01 PAR VALUE

             9 3/4% SERIES A CUMULATIVE REDEEMABLE PREFERRED SHARES
                OF BENEFICIAL INTEREST, $.01 PAR VALUE PER SHARE
                   (LIQUIDATION PREFERENCE $25.00 PER SHARE)

          Securities registered pursuant to Section 12(g) of the Act:

                                      NONE

    Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days.  Yes /X/    No / /

    Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K.  / /

    As of March 2, 2000, the aggregate market value of common shares of
beneficial interest held by non-affiliates of the registrant was $167,348,574.

    The number of shares of the registrant's common shares of beneficial
interest, $.01 par value, outstanding as of March 2, 2000 was 16,298,329.

                      DOCUMENTS INCORPORATED BY REFERENCE:

                                                  None.

--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
<PAGE>
    Great Lakes REIT, a Maryland real estate investment trust (the "Company"),
hereby amends Items 8 and 14(a) of its Form 10-K for the fiscal year ended
December 31, 1999, as filed with the Securities and Exchange Commission on March
23, 2000. This amendment is being filed to correct an error on page F-3. The
year identification in the column headings of the consolidated balance sheet are
incorrect. The proper headings are 1999 and 1998 for the left and right column,
respectively. The Company is filing the corrected financial statements and
supplementary data required by Regulation S-X that were included in the original
10-K filing commencing on page F-1 in their entirety.
<PAGE>
                                GREAT LAKES REIT
                         INDEX TO FINANCIAL STATEMENTS
                                  (ITEM 14(A))

<TABLE>
<S>                                                           <C>
Financial Statements

  Report of Independent Auditors............................     F-2

  Consolidated Balance Sheets as of December 31, 1999 and
    1998....................................................     F-3

  Consolidated Statements of Income for the years ended
    December 31, 1999, 1998 and 1997........................     F-4

  Consolidated Statements of Changes in Shareholders' Equity
    for the years ended December 31, 1999, 1998 and 1997....     F-5

  Consolidated Statements of Cash Flows for the years ended
    December 31, 1999, 1998 and 1997........................     F-6

  Notes to Consolidated Financial Statements................     F-7

Financial Statement Schedules

  Schedule III--Real Estate and Accumulated Depreciation as
    of December 31, 1999....................................     S-1
</TABLE>

    Schedules, other than as listed above, are omitted for the reason that they
are not applicable or equivalent information has been included elsewhere herein.

                                      F-1
<PAGE>
                         REPORT OF INDEPENDENT AUDITORS

The Board of Trustees and Shareholders
Great Lakes REIT

    We have audited the accompanying consolidated balance sheets of Great Lakes
REIT as of December 31, 1999 and 1998 and the related consolidated statements of
income, changes in shareholders' equity, and cash flows for each of the three
years in the period ended December 31, 1999. Our audit also included the
financial statement schedule listed in the index at Item 14(a). These financial
statements and schedule are the responsibility of the Company's management. Our
responsibility is to express an opinion on these financial statements and
schedule based on our audits.

    We conducted our audits in accordance with auditing standards generally
accepted in the United States. Those standards require that we plan and perform
the audit to obtain reasonable assurance about whether the financial statements
are free of material misstatement. An audit includes examining, on a test basis,
evidence supporting the amounts and disclosures in the financial statements. An
audit also includes assessing the accounting principles used and significant
estimates made by management, as well as evaluating the overall financial
statement presentation. We believe that our audits provide a reasonable basis
for our opinion.

    In our opinion, the financial statements referred to above present fairly,
in all material respects, the consolidated financial position of Great Lakes
REIT at December 31, 1999 and 1998, and the consolidated results of its
operations and its cash flows for each of the three years in the period ended
December 31, 1999 in conformity with accounting principles generally accepted in
the United States. Also, in our opinion, the related financial statement
schedule, when considered in relation to the basic financial statements taken as
a whole, presents fairly in all material respects the information set forth
therein.

                                          Ernst & Young LLP

Chicago, Illinois
January 26, 2000

                                      F-2
<PAGE>
                                GREAT LAKES REIT

                          CONSOLIDATED BALANCE SHEETS

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

<TABLE>
<CAPTION>
                                                                 DECEMBER 31,
                                                              -------------------
                                                                1999       1998
                                                              --------   --------
<S>                                                           <C>        <C>
                           ASSETS
Properties:
Land........................................................  $ 60,983   $ 60,960
Buildings, improvements, and equipment......................   410,478    388,068
                                                              --------   --------
                                                               471,461    449,028
Less accumulated depreciation...............................    33,074     22,166
                                                              --------   --------
                                                               438,387    426,862
Cash and cash equivalents...................................     1,518      2,466
Real estate tax escrows.....................................       277        619
Rents receivable............................................     6,274      5,021
Deferred financing and leasing costs, net of accumulated
  amortization..............................................     6,069      6,067
Goodwill, net of accumulated amortization...................     1,210      1,284
Other assets................................................     1,467      1,370
                                                              --------   --------
Total assets................................................  $455,202   $443,689
                                                              ========   ========

            LIABILITIES AND SHAREHOLDERS' EQUITY
Bank loan payable...........................................  $107,000   $ 84,291
Mortgage loans payable......................................   100,113    104,532
Bonds payable...............................................     4,550      4,800
Accounts payable and accrued liabilities....................     5,947      4,338
Accrued real estate taxes...................................    11,687     11,149
Prepaid rent................................................     3,936      3,220
Security deposits...........................................     1,084      1,107
                                                              --------   --------
Total liabilities...........................................   234,317    213,437
                                                              --------   --------
Minority interests..........................................       951      1,165
                                                              --------   --------

Commitments and contingencies
Preferred shares of beneficial interest ($0.01 par value,
  10,000,000 shares authorized; 1,500,000 9 3/4% Series A
  Cumulative Redeemable shares, with a $25.00 per share
  Liquidation Preference, issued and outstanding)...........    37,500     37,500
Common shares of beneficial interest ($0.01 par value,
  60,000,000 shares authorized; 17,816,883 and 17,513,578
  shares issued in 1999 and 1998, respectively).............       178        175
Paid-in-capital.............................................   227,907    223,414
Retained earnings (deficit).................................    (5,936)    (8,790)
Employee share purchase loans...............................   (16,335)   (11,967)
Deferred compensation.......................................       (22)       (44)
Treasury shares, at cost (1,521,785 and 743,184 shares in
  1999 and 1998, respectively)..............................   (23,358)   (11,201)
                                                              --------   --------
Total shareholders' equity..................................   219,934    229,087
                                                              --------   --------
Total liabilities and shareholders' equity..................  $455,202   $443,689
                                                              ========   ========
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-3
<PAGE>
                                GREAT LAKES REIT

                       CONSOLIDATED STATEMENTS OF INCOME

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

<TABLE>
<CAPTION>
                                                                 YEARS ENDED DECEMBER 31
                                                           ------------------------------------
                                                              1999         1998         1997
                                                           ----------   ----------   ----------
<S>                                                        <C>          <C>          <C>
Revenues:
Rental...................................................  $   73,822   $   62,803   $   36,399
Reimbursements...........................................      20,125       17,141       10,688
Interest and other.......................................       1,484          954          576
                                                           ----------   ----------   ----------
Total revenues...........................................      95,431       80,898       47,663
                                                           ----------   ----------   ----------
Expenses:
Real estate taxes........................................      15,254       12,634        7,702
Other property operating.................................      24,955       21,018       11,958
General and administrative...............................       4,692        4,958        3,379
Interest.................................................      14,009       12,339        4,308
Depreciation and amortization............................      15,901       13,092        8,200
                                                           ----------   ----------   ----------
Total expenses...........................................      74,811       64,041       35,547
                                                           ----------   ----------   ----------
Income before gain on sale of properties.................      20,620       16,857       12,116
Gain on sale of properties, net..........................       8,076
                                                           ----------   ----------   ----------
Income before allocation to minority interests...........      28,696       16,857       12,116
Minority interests.......................................          98           61           11
                                                           ----------   ----------   ----------
Net income...............................................      28,598       16,796       12,105
Income allocated to preferred shareholders...............       3,656          163
                                                           ----------   ----------   ----------
Net income applicable to common shares...................  $   24,942   $   16,633   $   12,105
                                                           ==========   ==========   ==========
Earnings per common share--basic.........................  $     1.51   $     0.99   $     0.92
                                                           ==========   ==========   ==========
Weighted average common shares outstanding--basic........  16,470,589   16,793,410   13,140,124
                                                           ==========   ==========   ==========
Diluted earnings per common share........................  $     1.51   $     0.98   $     0.91
                                                           ==========   ==========   ==========
Weighted average common shares outstanding--diluted......  16,554,163   16,974,311   13,304,540
                                                           ==========   ==========   ==========
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-4
<PAGE>
                                GREAT LAKES REIT

           CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY

             FOR THE YEARS ENDED DECEMBER 31, 1999, 1998, AND 1997

                             (DOLLARS IN THOUSANDS)

<TABLE>
<CAPTION>
                                                                1999       1998       1997
                                                              --------   --------   --------
<S>                                                           <C>        <C>        <C>
PREFERRED SHARES
Balance at beginning of period..............................  $ 37,500              $      2
Cancellation of preferred shares............................                              (2)
Proceeds from the sale of preferred shares..................             $ 37,500
                                                              --------   --------   --------
Balance at end of period....................................    37,500     37,500
                                                              --------   --------   --------
COMMON SHARES
Balance at beginning of period..............................       175        159         88
Net proceeds from the sale of common shares.................                   11         66
Exercise of share options...................................         3          5          4
Issuance of shares for property acquisitions................                               1
                                                              --------   --------   --------
Balance at end of period....................................       178        175        159
                                                              --------   --------   --------
PAID-IN CAPITAL
Balance at beginning of period..............................   223,414    196,431     98,096
Net proceeds from the sale of common shares.................               19,660     92,940
Exercise of share options...................................     4,493      7,323      3,860
Issuance of shares for property acquisitions................                           1,535
                                                              --------   --------   --------
Balance at end of period....................................   227,907    223,414    196,431
                                                              --------   --------   --------
RETAINED EARNINGS (DEFICIT)
Balance at beginning of period..............................    (8,790)    (4,501)       177
Net income..................................................    28,598     16,796     12,105
Distributions/dividends.....................................   (25,744)   (21,085)   (16,783)
                                                              --------   --------   --------
Balance at end of period....................................    (5,936)    (8,790)    (4,501)
                                                              --------   --------   --------
EMPLOYEE SHARE PURCHASE LOANS
Balance at beginning of period..............................   (11,967)    (4,654)    (1,247)
Exercise of share options...................................    (4,368)    (7,313)    (3,407)
                                                              --------   --------   --------
Balance at end of period....................................   (16,335)   (11,967)    (4,654)
                                                              --------   --------   --------
DEFERRED COMPENSATION
Balance at beginning of period..............................       (44)       (73)      (251)
Amortization of deferred compensation.......................        22         29        178
                                                              --------   --------   --------
Balance at end of period....................................       (22)       (44)       (73)
                                                              --------   --------   --------
TREASURY SHARES
Balance at beginning of period..............................   (11,201)      (270)      (270)
Purchase of treasury shares.................................   (12,157)   (10,931)
                                                              --------   --------   --------
Balance at end of period....................................   (23,358)   (11,201)      (270)
                                                              --------   --------   --------
Total shareholders' equity..................................  $219,934   $229,087   $187,092
                                                              ========   ========   ========
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-5
<PAGE>
                                GREAT LAKES REIT

                     CONSOLIDATED STATEMENTS OF CASH FLOWS

                             (DOLLARS IN THOUSANDS)

<TABLE>
<CAPTION>
                                                                  YEARS ENDED DECEMBER 31,
                                                              --------------------------------
                                                                1999       1998        1997
                                                              --------   ---------   ---------
<S>                                                           <C>        <C>         <C>
CASH FLOWS FROM OPERATING ACTIVITIES
Net income..................................................  $28,598    $  16,796   $  12,105
Adjustments to reconcile net income to cash flows from
  operating activities
  Depreciation and amortization.............................   15,901       13,092       8,200
  Gain on sale of properties, net...........................   (8,076)
  Other non-cash items......................................      120           90         178
Net changes in assets and liabilities:
  Rents receivable..........................................   (1,253)      (1,742)     (1,148)
  Real estate tax escrows and other assets..................      245         (312)        421
  Accounts payable, accrued expenses and other
    liabilities.............................................    2,160        1,645       1,151
  Accrued real estate taxes.................................      538        3,372       2,354
  Payment of deferred leasing costs.........................   (2,109)      (2,609)     (1,832)
                                                              -------    ---------   ---------
Net cash provided by operating activities...................   36,124       30,332      21,429
                                                              -------    ---------   ---------
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of properties......................................  (28,600)    (128,923)    (97,758)
Additions to buildings, improvements and equipment..........  (13,030)     (11,439)     (5,999)
Proceeds from property sales, net...........................   22,669
Other investing activities..................................                 1,310        (300)
                                                              -------    ---------   ---------
Net cash used by investing activities.......................  (18,961)    (139,052)   (104,057)
                                                              -------    ---------   ---------
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from sale of common and preferred shares...........                60,000     101,603
Payment of share offering costs.............................                (2,829)     (8,599)
Proceeds from exercise of share options.....................      128           15         457
Proceeds from bank and mortgage loans payable...............   38,774      264,035     100,425
Distributions / dividends paid..............................  (25,602)     (20,922)    (16,783)
Distributions to minority interests.........................      (56)         (96)
Purchase of minority interests..............................     (256)
Purchase of treasury shares.................................  (12,157)     (10,931)
Payment of bank and mortgage loans and bonds................  (18,655)    (177,945)    (94,428)
Payment of deferred financing costs.........................     (287)      (1,578)       (298)
                                                              -------    ---------   ---------
Net cash provided by (used in) financing activities.........  (18,111)     109,749      82,377
                                                              -------    ---------   ---------
Net increase (decrease) in cash and cash equivalents........     (948)       1,029        (251)
Cash and cash equivalents, beginning of year................    2,466        1,437       1,688
                                                              -------    ---------   ---------
Cash and cash equivalents, end of year......................  $ 1,518    $   2,466   $   1,437
                                                              =======    =========   =========
Supplemental disclosure of cash flow:
Interest paid...............................................  $13,937    $  12,165   $   4,136
                                                              =======    =========   =========
Non-cash financing transactions:
Employee share purchase loans...............................  $ 4,368    $   7,313   $   3,407
                                                              =======    =========   =========
Mortgage assumed by purchaser of property...................  $ 2,079
                                                              =======    =========   =========
Increase in preferred dividends payable.....................  $   142    $     163
                                                              =======    =========   =========
Issuance of shares and units to acquire properties..........             $     887   $   1,536
                                                              =======    =========   =========
Mortgages assumed to acquire properties.....................             $  12,435   $   2,989
                                                              =======    =========   =========
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-6
<PAGE>
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

    NATURE OF ACTIVITIES

    Great Lakes REIT, a Maryland real estate investment trust, (the "Company"),
was formed in 1992 to invest in income-producing real property. The principal
business of the Company is the ownership, management, leasing, renovation and
acquisition of suburban office and light industrial properties primarily located
in the Midwest. At December 31, 1999, the Company owned and operated 36
properties primarily located in suburban areas of Chicago, Detroit, Milwaukee,
Denver, Cincinnati, Columbus and Minneapolis. The Company leases office and
light industrial space to over 500 tenants in a variety of businesses.

    PRINCIPLES OF CONSOLIDATION

    The consolidated financial statements include the accounts of the Company
and its wholly owned subsidiaries and controlled partnership. Intercompany
accounts and transactions have been eliminated in consolidation.

    PROPERTIES

    Costs incurred for the acquisition, development, construction and
improvement of properties are capitalized. Certain costs of yet-to-be acquired
properties, including deposits and professional fees, are capitalized as other
assets. These costs are subsequently capitalized as property acquisition costs
or charged to expense when it becomes apparent that acquisition of a particular
property is not probable. Maintenance and repairs are charged to expense when
incurred.

    Depreciation of buildings is computed using the straight-line method over
the estimated useful lives of the assets, generally 40 years. Depreciation of
tenant improvements is computed using the straight-line method over the shorter
of the lease term or useful life. For the years ended December 31, 1999, 1998
and 1997, depreciation expense amounted to $13,877, $11,453 and $6,463,
respectively.

    The Company recognizes impairment losses for its properties when indicators
of impairment are present and a property's expected undiscounted cash flows are
not sufficient to recover the property's carrying amount.

    DEFERRED COSTS

    Deferred costs consist principally of financing fees and leasing commissions
that are amortized over the terms of the respective agreements.

    REVENUE RECOGNITION

    Minimum rentals are recognized on a straight-line basis over the term of the
related leases. Deferred rents receivable at December 31, 1999 and 1998 were
$4,917 and $4,437, respectively. Additional rents from expense reimbursements
for common area maintenance expenses and real estate taxes are recognized in the
period in which the related expenses are incurred.

                                      F-7
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
    CASH EQUIVALENTS

    The Company considers all highly liquid investments purchased with a
maturity of three months or less to be cash equivalents. At December 31, 1999
and 1998, the Company had $1,336 and $2,449, respectively, in a money market
fund.

    INCOME TAXES

    The Company has elected to be treated as a real estate investment trust
("REIT") under the applicable provisions of the Internal Revenue Code of 1986,
as amended. In order to qualify as a REIT, the Company is required to distribute
to shareholders at least 95% of its taxable income and to meet certain asset and
income tests as well as certain other requirements. Accordingly, no provision
for income taxes has been reflected in the consolidated financial statements.

    As of December 31, 1999, properties, rents receivable, goodwill and prepaid
rent have a federal income tax basis of approximately $438,981, $1,358, $-0- and
$-0-, respectively.

    SHARE OPTIONS

    The Company has elected to follow Accounting Principles Board Opinion
No. 25, "Accounting for Stock Issued to Employees" (APB 25), in accounting for
its options on common shares. Under APB 25, no compensation expense is
recognized because the exercise price of the Company's employee share options
equals or exceeds the market price of the underlying shares at the date of
grant.

    INTEREST RATE CAP AGREEMENT

    The Company purchased an interest rate cap agreement to hedge its exposure
to increases in interest costs under its variable rate debt. The one-time
premium paid by the Company is included in deferred financing costs and is
amortized over the term of the agreement using the straight-line method. Net
amounts paid or received under the agreement are recognized as an adjustment to
interest expense when such amounts are incurred or earned. The Company is
exposed to credit loss in the event of non-performance by counterparties under
the agreement, but the Company does not expect non-performance by any of these
counterparties. The amount of such exposure is generally limited to the amount
of any payments due but not yet received from the counterparty.

    USE OF ESTIMATES

    The preparation of financial statements in conformity with accounting
principles generally accepted in the United States requires management to make
estimates and assumptions that affect the amounts reported in the financial
statements and accompanying notes. Actual results could differ from those
estimates.

    RECLASSIFICATIONS

    Certain accounts in 1998 and 1997 have been reclassified to conform with the
1999 presentation. Such reclassifications did not effect the results of
operations.

                                      F-8
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

2. DEFERRED COSTS

    Deferred costs consisted of the following at December 31, 1999 and 1998:

<TABLE>
<CAPTION>
                                                                1999       1998
                                                              --------   --------
<S>                                                           <C>        <C>
Deferred financing costs....................................   $2,990     $3,017
Deferred leasing costs......................................    7,659      6,499
                                                               ------     ------
                                                               10,649      9,516
Less accumulated amortization...............................    4,580      3,449
                                                               ------     ------
                                                               $6,069     $6,067
                                                               ======     ======
</TABLE>

    During the years ended December 31, 1999, 1998 and 1997, amortization of
financing costs was $526, $574 and $1,099, respectively, and amortization of
leasing costs was $1,424, $990 and $563, respectively.

3. LONG-TERM DEBT

    Mortgage loans payable aggregated $100,113 and $104,532 at December 31, 1999
and 1998, respectively. The mortgage loans payable require monthly payments of
principal and interest. Interest rates at December 31, 1999, ranged from 6.83%
to 8.95%.

    The Company has obtained a bank letter of credit to secure repayment of the
bonds payable in a face amount of approximately $4,600. The Company has
guaranteed repayment of the letter of credit to the issuing bank as well as
granted the issuing bank a first mortgage on the property. The interest rate on
the bonds (5.4% per annum at December 31, 1999) is reset weekly by the bond
placement agent.

    The Company has a $150,000 unsecured bank credit facility with a maturity
date of April 2001. The unsecured credit facility bears interest at LIBOR plus
1.0% to 1.3% depending on overall company leverage (7.4875% at December 31,
1999).

    In June 1999, the Company entered into an interest rate cap agreement with a
major financial institution whereby the Company has limited the LIBOR interest
rate on $50,000 of its variable rate debt to no more than 6% per annum until
June 2001. The cost of this agreement to the Company was $209 and is being
amortized to expense over the period of the agreement (24 months).

    The following is a summary of principal maturities of mortgage loans, bank
loan and bonds payable:

<TABLE>
<CAPTION>
YEAR ENDING DECEMBER 31,                                       AMOUNT
------------------------                                      --------
<S>                                                           <C>
2000........................................................  $  2,764
2001........................................................  $109,970
2002........................................................  $  3,191
2003........................................................  $ 14,236
2004........................................................  $  5,855
Thereafter..................................................  $ 75,647
</TABLE>

    At December 31, 1999, properties with a carrying amount of approximately
$137,836 were pledged as collateral under the various debt agreements.

                                      F-9
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

4. SHARE OPTIONS

    The Company has a share option plan that provides for the granting of
options on common shares to non-employee trustees. At December 31, 1999, options
on 80,590 shares were available for future grant.

    In 1997, the Company adopted the 1997 Equity and Performance Incentive Plan
(the "1997 Plan") which superseded the Company's prior plan. The 1997 Plan
provides that 2,250,000 common shares of beneficial interest were reserved for
issuance to Company employees. At December 31, 1999, options on 296,700 shares
were available for future grant under the 1997 Plan.

    For options granted in 1999, 1998 and 1997, the exercise prices at the dates
of grant were equal to or greater than the fair value of the Company's shares.

    A summary of the Company's share option activity and related information for
the years ended December 31, 1999, 1998 and 1997 is as follows:

<TABLE>
<CAPTION>
                                                                WTD. AVG. EXERCISE
                                                     SHARES      PRICE PER SHARE
                                                    ---------   ------------------
<S>                                                 <C>         <C>
Outstanding at 1/1/97.............................    601,628         $11.69
Granted...........................................  1,343,000         $16.52
Exercised.........................................    370,725         $11.30
                                                    ---------
Outstanding at 1/1/98.............................  1,573,903         $15.91
Granted...........................................    289,900         $16.21
Exercised.........................................    472,358         $15.78
Cancelled.........................................      3,000         $16.00
                                                    ---------
Outstanding at 1/1/99.............................  1,388,445         $16.03
Granted...........................................    301,400         $14.89
Exercised.........................................    303,305         $14.84
Cancelled.........................................     11,500         $16.31
                                                    ---------
Outstanding at 12/31/99...........................  1,375,040         $16.04
Exercisable at 12/31/97...........................    779,847         $15.29
Exercisable at 12/31/98...........................  1,104,010         $15.84
Exercisable at 12/31/99...........................    929,795         $16.33
</TABLE>

    The weighted average fair value of options granted is as follows:

<TABLE>
<CAPTION>
                                           WHERE THE SHARE PRICE       WHERE THE SHARE PRICE IS
                                         EQUALS THE EXERCISE PRICE   LESS THAN THE EXERCISE PRICE
                                         -------------------------   ----------------------------
<S>                                      <C>                         <C>
1999..................................             $1.17
1998..................................             $3.08
1997..................................             $3.18                          $1.43
</TABLE>

    Pro forma information regarding net income and earnings per share is
required by FASB Statement 123 "Accounting for Stock-Based Compensation," and
has been determined as if the Company had accounted for its employee share
options under the fair value method of that Statement. The fair value for

                                      F-10
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

4. SHARE OPTIONS (CONTINUED)
these options was estimated at the date of grant using a Black-Scholes option
pricing model with the following weighted-average assumptions:

<TABLE>
<CAPTION>
                                                RISK-FREE       DIVIDEND     VOLATILITY   WEIGHTED AVERAGE
                                              INTEREST RATE      YIELDS       FACTORS      EXPECTED LIFE
                                              -------------   ------------   ----------   ----------------
<S>                                           <C>             <C>            <C>          <C>
1999.......................................       6.50%         9.1%-9.4%       0.212%      5 years
1998.......................................       5.00%       7.88%-8.11%       0.394%      5 years
1997.......................................       5.75%        6.17%-7.5%       0.341%      3 years
</TABLE>

    The Black-Scholes option valuation model was developed for use in estimating
the fair value of traded options that have no vesting restrictions and are fully
transferable. In addition, option valuation models require the input of highly
subjective assumptions including the expected stock price volatility. Because
the Company's employee share options have characteristics significantly
different from those of traded options, and because changes in the subjective
input assumptions can materially affect the fair value estimate, in management's
opinion, the existing models do not necessarily provide a reliable single
measure of the fair value of its employee share options.

    The effects on 1999 and 1998 pro forma net income and pro forma earnings per
common share, both basic and diluted, of amortizing to expense the estimated
fair value of share options are not necessarily representative of the effects on
net income to be reported in future years due to such things as the vesting
period of the share options, and the potential for issuance of additional share
options in future years.

    For purposes of pro forma disclosures, the estimated fair value of the
options is amortized to expense over the options' vesting period. The Company's
unaudited pro forma information follows for the years ended December 31, 1999
and 1998:

<TABLE>
<CAPTION>
                                                              1999       1998
                                                            --------   --------
<S>                                                         <C>        <C>
Pro forma net income......................................  $24,447    $15,902
Pro forma basic earnings per common share.................  $  1.48    $   .95
Pro forma diluted earnings per common share...............  $  1.48    $   .94
</TABLE>

    The Company has a limited purpose employee loan program whereby employees
may borrow a portion of the cost of exercising options on common shares held by
the employee. Such loans bear interest at the Company's cost of funds which is
payable quarterly, are recourse to the employees, have a term of five years
provided the employee remains employed by the Company, and are secured by a
pledge of the common shares acquired by the employee through this program. As of
December 31, 1999, employees had acquired approximately 1,119,000 common shares
through this program with outstanding loan amounts of $16,335 due the Company.
Such amount is reflected as a reduction of shareholders' equity until the loans
are repaid.

5. SHARE OFFERINGS

    In December 1998, the Company sold 1.5 million shares of 9 3/4% Series A
Cumulative Redeemable Preferred Shares of Beneficial Interest. Net proceeds of
approximately $36,200 were used to repay a portion of its unsecured credit
facility.

    In April 1998, the Company sold 1,184,211 common shares to a newly formed
unit investment trust. Net proceeds of approximately $21,000 were used to repay
a portion of its unsecured credit facility.

                                      F-11
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

5. SHARE OFFERINGS (CONTINUED)
    In May 1997, the Company closed the initial public offering of its common
shares. The Company sold 6.55 million common shares at the price of $15.50 per
share, including shares issued upon exercise of the underwriters' over allotment
option. Net proceeds to the Company were approximately $93,000, substantially
all of which was used to repay its bank lines of credit and other indebtedness
including certain mortgage debt on the Company's properties.

    In February 1997, the Company issued 118,134 common shares with a total
value at issuance of $1,536 in connection with the acquisition of the Markham,
Illinois and Elgin, Illinois properties.

6. LEASES

    The Company leases office and industrial properties to tenants under
noncancellable operating leases that expire at various dates through 2010. The
lease agreements typically provide for a specific monthly payment plus
reimbursement of certain operating expenses. The following is a summary of
minimum future rental revenue under noncancellable operating leases:

<TABLE>
<CAPTION>
YEAR ENDING DECEMBER 31,                                       AMOUNT
------------------------                                      --------
<S>                                                           <C>
2000........................................................  $ 69,122
2001........................................................    55,645
2002........................................................    44,009
2003........................................................    27,879
2004........................................................    14,921
Thereafter..................................................    24,228
                                                              --------
                                                              $235,804
                                                              ========
</TABLE>

    Minimum future rentals do not include amounts that are received from tenants
as a reimbursement of property operating expenses.

7. DISTRIBUTIONS

    The Company declared periodic distributions of $22,088, $20,922 and $16,783,
to common shareholders of record during the calendar years 1999, 1998 and 1997,
respectively. The Company has determined the common shareholders' treatment for
Federal income tax purposes to be as follows:

<TABLE>
<CAPTION>
                                                     1999       1998       1997
                                                   --------   --------   --------
<S>                                                <C>        <C>        <C>
Ordinary income..................................  $17,947    $18,217    $14,848
Unrecaptured Section 1250 gain...................      529
20% rate capital gains...........................    3,612
Return of capital................................               2,705      1,935
                                                   -------    -------    -------
Total............................................  $22,088    $20,922    $16,783
                                                   =======    =======    =======
</TABLE>

    The Company paid dividends to preferred shareholders of record in 1999 of
$3,514, all of which represented ordinary income for Federal income tax purposes
to the preferred shareholders.

                                      F-12
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

8. PROPERTY ACQUISITIONS

    The following properties were acquired in 1999 and 1998 and the results of
their operations are included in the consolidated statements of income from
their respective dates of acquisition.

<TABLE>
<CAPTION>
                                                                               TOTAL ACQUISITION
                                                                                     PRICE
                                                                              -------------------
LOCATION                                                      DATE ACQUIRED     1999       1998
--------                                                      -------------   --------   --------
<S>                                                           <C>             <C>        <C>
Burlington Office Center
305, 315, 325 E. Eisenhower Pkwy.
Ann Arbor, MI...............................................     5/11/99      $19,632

One Riverwood Place
N17 W. 24222 Riverwood Dr.
Pewaukee, WI................................................     12/1/99        8,968

175 S. Third St.
Columbus, OH................................................      1/7/98                 $21,949

Milwaukee Center
111 E. Kilbourn Ave.
Milwaukee, WI...............................................     4/15/98                  46,794

116 Inverness Dr. East
Englewood, CO...............................................     5/22/98                  20,967

183 Inverness Dr. West
Englewood, CO...............................................     5/22/98                  20,168

Court International I
2550 University Ave. West
St. Paul, MN................................................     7/30/98                   9,772

3030 Warrenville Rd.
Lisle, IL...................................................      9/1/98                  18,087

191 Waukegan Rd.
Northfield, IL..............................................     9/24/98                   4,508
</TABLE>

                                      F-13
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

9. PROPERTY DISPOSITIONS

    The Company sold five properties in 1999 as follows:

<TABLE>
<CAPTION>
                                                                                            MORTGAGE
                                                      DATE OF    CONTRACT   GAIN (LOSS)     ASSUMED
PROPERTY                                                SALE      PRICE       ON SALE     BY PURCHASER
--------                                              --------   --------   -----------   ------------
<S>                                                   <C>        <C>        <C>           <C>
1675 Holmes Rd.
Elgin, IL..........................................    4/21/99   $ 4,700       $  658        $2,079

2800 River Rd.
Des Plaines, IL....................................    6/30/99   $ 8,050       $2,982

1251 Plum Grove Rd.
Schaumburg, IL.....................................    6/30/99   $ 3,550       $1,875

565 Lakeview Pkwy.
Vernon Hills, IL...................................    8/25/99   $ 8,800       $3,190

16601 S. Kedzie Ave.
Markham, IL........................................   12/10/99   $   513       ($ 629)
                                                                 -------       ------        ------

  Totals                                                         $25,613       $8,076        $2,079
                                                                 =======       ======        ======
</TABLE>

    The sales proceeds of the Elgin, Illinois property were reinvested in
Burlington Office Center, Ann Arbor, Michigan in a tax-deferred exchange. The
sales proceeds of the 565 Lakeview Parkway, Vernon Hills, Illinois property were
reinvested in One Riverwood Place, Pewaukee, Wisconsin in a tax-deferred
exchange.

10. SEGMENT INFORMATION

    The Company has three reportable segments distinguished by property type.
The property types are office, with 89% (as measured by square feet at
December 31, 1999) of the Company's overall portfolio, office/service center
(11%), and industrial (0%, the Company sold its only industrial property in
1999), and are principally located in the Midwest. As of December 31, 1999, the
properties were leased to more than 500 tenants, no single tenant accounted for
more than 5% of the aggregate annualized base rent of the Company's portfolio
and only 20 tenants individually represented more than 1% of such aggregate
annualized base rent.

    The Company evaluates performance and allocates resources based on property
revenues (rental and reimbursement income) less property operating expenses and
real estate taxes to arrive at net operating income--a widely recognized
industry measure of a property's performance.

                                      F-14
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

10. SEGMENT INFORMATION (CONTINUED)
    Following is a summary report of segment information for the years ended
December 31, 1999, 1998 and 1997.

<TABLE>
<CAPTION>
                                                  1999       1998       1997
                                                --------   --------   --------
<S>                                             <C>        <C>        <C>
Revenues
Office........................................  $ 86,223   $ 70,755   $ 39,581
Office/service center.........................     6,908      6,972      5,939
Industrial....................................       172        342        644
Deferred rental revenues......................       757      1,875        923
Interest and other............................     1,371        954        576
                                                --------   --------   --------
  Total.......................................  $ 95,431   $ 80,898   $ 47,663
                                                ========   ========   ========
Net operating income
Office........................................  $ 48,443   $ 39,512   $ 21,839
Office/service center.........................     4,511      4,703      4,167
Industrial....................................       140        202        498
                                                --------   --------   --------
  Total.......................................  $ 53,094   $ 44,417   $ 26,504
                                                ========   ========   ========
Depreciation and amortization
Office........................................  $ 14,008   $ 11,263   $  6,155
Office/service center.........................     1,329      1,105      1,048
Industrial....................................        33         88        132
Other.........................................       531        636        865
                                                --------   --------   --------
  Total.......................................  $ 15,901   $ 13,092   $  8,200
                                                ========   ========   ========
</TABLE>

                                      F-15
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

10. SEGMENT INFORMATION (CONTINUED)

<TABLE>
<CAPTION>
                                                  1999       1998       1997
                                                --------   --------   --------
<S>                                             <C>        <C>        <C>
Interest expense
Office........................................  $ 12,454   $ 10,902   $  3,226
Office/service center.........................     1,485      1,218        799
Industrial....................................        70        219        283
                                                --------   --------   --------
  Total.......................................  $ 14,009   $ 12,339   $  4,308
                                                ========   ========   ========
</TABLE>

<TABLE>
<CAPTION>
                                                          AS OF DECEMBER 31,
                                                          -------------------
                                                            1999       1998
                                                          --------   --------
<S>                                                       <C>        <C>
Assets
Office..................................................  $411,738   $394,607
Office/service center...................................    30,635     31,841
Industrial..............................................                3,949
Other...................................................    12,829     13,292
                                                          --------   --------
  Total.................................................  $455,202   $443,689
                                                          ========   ========
</TABLE>

<TABLE>
<CAPTION>
                                                                 YEARS ENDED DECEMBER 31,
                                                              ------------------------------
                                                                1999       1998       1997
                                                              --------   --------   --------
<S>                                                           <C>        <C>        <C>
Additions to properties
Office......................................................  $40,476    $152,790   $ 97,458
Office/service center.......................................      885         760      6,917
Industrial..................................................       36          36      3,838
Other.......................................................       45          84         69
                                                              -------    --------   --------
Total.......................................................  $41,442    $153,670   $108,282
                                                              =======    ========   ========
Income before gain on sale of properties
Office......................................................  $21,981    $ 17,347   $ 12,458
Office/service center.......................................    1,697       2,380      2,320
Industrial..................................................       37        (105)        83
Deferred rental revenue.....................................      757       1,875        923
Interest and other income...................................    1,371         954        576
General and administrative..................................   (4,692)     (4,958)    (3,379)
Other depreciation..........................................     (531)       (636)      (865)
                                                              -------    --------   --------
Income before gains on sales of properties..................  $20,620    $ 16,857   $ 12,116
                                                              =======    ========   ========
</TABLE>

                                      F-16
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

11. EARNINGS PER SHARE

    The following table sets forth the computation of basic and diluted earnings
per common share:

<TABLE>
<CAPTION>
                                                              1999         1998         1997
                                                           ----------   ----------   ----------
<S>                                                        <C>          <C>          <C>
Numerator:
Net income applicable to common shareholders.............  $   24,942   $   16,633   $   12,105
                                                           ----------   ----------   ----------
Numerator for basic earnings per common share............      24,942       16,633       12,105
Minority interests.......................................          98           61           11
                                                           ----------   ----------   ----------
Numerator for diluted earnings per common share..........  $   25,040   $   16,694   $   12,116
                                                           ==========   ==========   ==========
Denominator:
Denominator for basic earnings per common share
Weighted average shares..................................  16,470,589   16,793,410   13,140,124

Effect of dilutive securities:
Convertible operating partnership units..................      56,348       72,497       24,050
Employee share options...................................      27,226      108,404      140,366
                                                           ----------   ----------   ----------
Denominator for diluted earnings per common share........  16,554,163   16,974,311   13,304,540
                                                           ==========   ==========   ==========
Basic earnings per common share..........................  $     1.51   $     0.99   $     0.92
                                                           ==========   ==========   ==========
Diluted earnings per common share........................  $     1.51   $     0.98   $     0.91
                                                           ==========   ==========   ==========
</TABLE>

12. FAIR VALUE OF FINANCIAL INSTRUMENTS

    The Company discloses information concerning the fair value of financial
instruments for which it is practical to estimate such fair values. The carrying
amounts reported for cash and cash equivalents in the accompanying consolidated
balance sheets approximated its fair value. The fair market value of mortgages
payable at December 31, 1999 was $93,458 assuming a market interest rate of
8.25%. The carrying amount of mortgages payable at December 31, 1998
approximated fair value. The carrying amounts of bonds payable and bank loan
payable approximated fair value at December 31, 1999 and 1998. The interest rate
cap agreement (Note 3) had a fair value of $406 at December 31, 1999.

13. QUARTERLY FINANCIAL DATA (UNAUDITED)

<TABLE>
<CAPTION>
                                                          3/31/99    6/30/99    9/30/99    12/31/99
                                                          --------   --------   --------   --------
<S>                                                       <C>        <C>        <C>        <C>
Revenues................................................  $22,738    $23,924    $24,279    $24,490
Net income..............................................  $ 3,899    $ 8,867    $ 7,625    $ 4,551
Basic earnings per common share.........................  $  0.24    $  0.54    $  0.46    $  0.27
Diluted earnings per common share.......................  $  0.23    $  0.54    $  0.46    $  0.28
</TABLE>

<TABLE>
<CAPTION>
                                                          3/31/98    6/30/98    9/30/98    12/31/98
                                                          --------   --------   --------   --------
<S>                                                       <C>        <C>        <C>        <C>
Revenues................................................  $16,803    $19,490    $21,459    $23,146
Net income..............................................  $ 3,968    $ 4,161    $ 4,248    $ 4,256
Basic earnings per common share.........................  $  0.25    $  0.24    $  0.25    $  0.25
Diluted earnings per common share.......................  $  0.25    $  0.24    $  0.24    $  0.25
</TABLE>

                                      F-17
<PAGE>
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

14. PRO FORMA INFORMATION (UNAUDITED)

    The following unaudited pro forma summary presents information as if the
Company's property acquisitions, property dispositions and sales of common and
preferred shares through December 31, 1998 had occurred at the beginning of that
year. The pro forma information is provided for informational purposes only. It
is based on historical information and does not necessarily reflect the actual
results that would have occurred nor is it necessarily indicative of future
results of operations of the Company.

<TABLE>
<CAPTION>
                                                                1998
                                                              --------
<S>                                                           <C>
Total revenue...............................................  $89,068
Net income applicable to common shares......................  $15,757
Basic earnings per common share.............................  $  0.94
Diluted earnings per common share...........................  $  0.93
</TABLE>

                                      F-18
<PAGE>
                                  SCHEDULE III
                    REAL ESTATE AND ACCUMULATED DEPRECIATION
<TABLE>
<CAPTION>
                                                                                                         GROSS AMOUNT AT WHICH
                                                                               COSTS CAPITALIZED        CARRIED AT DECEMBER 31,
                                       INITIAL COST TO THE COMPANY         SUBSEQUENT TO ACQUISITION              1999
                                 ---------------------------------------   --------------------------   ------------------------
                                             (000'S OMITTED)                    (000'S OMITTED)             (000'S OMITTED)
                                                            BUILDINGS &                 BUILDINGS &                 BUILDINGS &
                                 ENCUMBRANCE      LAND     IMPROVEMENTS      LAND       IMPROVEMENTS      LAND     IMPROVEMENTS
                                 ------------   --------   -------------   ---------   --------------   --------   -------------
<S>                              <C>            <C>        <C>             <C>         <C>              <C>        <C>
1900 East Golf Rd.
Schaumburg, IL                                  $ 3,800      $ 20,212                     $ 1,922       $ 3,800      $ 22,134
1750 East Golf Rd.
Schaumburg, IL                                  $ 2,300      $ 17,607                     $   524       $ 2,300      $ 18,131
160-185 Hansen Court
Wood Dale, IL                                   $ 2,100      $  3,210                     $ 1,639       $ 2,100      $  4,849
3455, 3550, 3555 Salt Creek
Lane
Arlington Heights, IL                           $   850      $  4,333                     $   339       $   850      $  4,672
601 Campus Dr.
Arlington Heights, IL                   (B)     $   900      $  2,264                     $ 1,014       $   900      $  3,278
1011 Touhy Ave.
Des Plaines, IL                                 $   720      $  3,932                     $ 2,966       $   720      $  6,898
1660 Feehanville Dr.
Mount Prospect, IL                              $ 1,100      $  4,304                     $   615       $ 1,100      $  4,919
175 Hawthorn Pkwy.
Vernon Hills, IL                        (B)     $ 1,600      $  4,721                     $ 1,213       $ 1,600      $  5,934
Two Marriott Dr.
Lincolnshire, IL                        (B)     $   610      $  2,230                     $   177       $   610      $  2,407
3400 Dundee Rd.
Northbrook, IL                          (B)     $   607      $  3,476                     $   913       $   607      $  4,389
3010 & 3020 Wood Creek Dr.
Downers Grove, IL                       (B)     $ 2,385      $  6,988                     $   442       $ 2,385      $  7,430
823 Commerce Dr.
Oak Brook, IL                                   $   500      $  1,262                     $ 3,264       $   500      $  4,526
3030 Warrenville Rd.
Lisle, IL                                       $ 4,300      $ 13,787                     $   323       $ 4,300      $ 14,110
191 Waukegan Rd.
Northfield, IL                                  $ 1,220      $  3,288                     $   264       $ 1,220      $  3,552
11270 W. Park Place
Milwaukee, WI                           (B)     $   940      $ 14,734                     $   725       $   940      $ 15,459
11925 W. Lake Park Dr.
Milwaukee, WI                           (B)     $   319      $  1,819                     $   241       $   319      $  2,060
2514 S. 102nd St. &
10150 W. National Ave.
West Allis, WI                          (B)     $   975      $  7,020                     $   680       $   975      $  7,700
150, 175, 250 Patrick Blvd.
Brookfield, WI                     $ 3,078      $ 2,600      $  3,967                     $   715       $ 2,600      $  4,682
375 Bishop's Way
Brookfield, WI                                  $   600      $  4,361                     $   352       $   600      $  4,713
111 East Kilbourn Ave.
Milwaukee, WI                                   $ 2,176      $ 44,618                     $ 1,903       $ 2,176      $ 46,521
N17 W24222 Riverwood Dr.
Pewaukee, WI                                    $   771      $  8,197                     $   268       $   771      $  8,465
2550 University Ave. West
St. Paul, MN                                    $ 1,280      $ 22,820                     $   449       $ 1,280      $ 23,269
2221 University Ave. SE
Minneapolis, MN                    $ 4,550      $ 1,100      $  7,090                     $   170       $ 1,100      $  7,260
777 East Eisenhower Pkwy.
Ann Arbor, MI                                   $ 4,000      $ 12,664                     $ 5,887       $ 4,000      $ 18,551
32255 Northwestern Highway
Farmington Hills, MI               $11,745      $ 3,700      $ 20,802                     $ 1,542       $ 3,700      $ 22,344
1301 W. Long Lake Rd.
Troy, MI                                (B)     $ 2,500      $ 13,600                     $ 1,160       $ 2,500      $ 14,760
No. 40 OakHollow
Southfield, MI                          (B)     $ 1,250      $  6,063                     $   466       $ 1,250      $  6,529
24800 Denso Dr.
Southfield, MI                          (B)     $ 1,400      $  4,547                     $   882       $ 1,400      $  5,429
305, 315, 325 E. Eisenhower
Pkwy.
Ann Arbor, MI                                   $ 3,200      $ 16,432                     $   255       $ 3,200      $ 16,687
655 Metro Place South
Dublin, OH                                      $ 1,470      $ 18,188                     $ 1,040       $ 1,470      $ 19,228
4860-5000 Blazer Memorial Pkwy.
Dublin, OH                                      $ 1,340      $  7,042                     $   646       $ 1,340      $  7,688
425 Metro Place North
Dublin, OH                                      $   620      $  6,666                     $   662       $   620      $  7,328
175 South Third St.
Columbus, OH                                      Lease      $ 21,949                     $   678         Lease      $ 22,627
30 Merchant St.
Springdale, OH                                  $   650      $  5,496                     $ 1,148       $   650      $  6,644
116 Inverness Dr. East
Englewood, CO                      $12,110      $ 3,100      $ 17,867                     $   564       $ 3,100      $ 18,431
183 Inverness Dr. West
Englewood, CO                                   $ 4,000      $ 16,168                     $   194       $ 4,000      $ 16,362
                                   -------      -------      --------                     -------       -------      --------
Totals.........................    $31,483      $60,983      $373,724                     $36,242       $60,983      $409,966
                                   =======      =======      ========                     =======       =======      ========

<CAPTION>

                                            ACCUMULATED      DATE      METHOD OF
                                  TOTAL     DEPRECIATION   ACQUIRED   DEPRECIATION
                                 --------   ------------   --------   ------------
<S>                              <C>        <C>            <C>        <C>
1900 East Golf Rd.
Schaumburg, IL                   $ 25,934     $ 1,933       Dec-96         (A)
1750 East Golf Rd.
Schaumburg, IL                   $ 20,431     $ 1,152       Sep-97         (A)
160-185 Hansen Court
Wood Dale, IL                    $  6,949     $ 1,143       Jan-94         (A)
3455, 3550, 3555 Salt Creek
Lane
Arlington Heights, IL            $  5,522     $   284       Oct-97         (A)
601 Campus Dr.
Arlington Heights, IL            $  4,178     $   978       May-93         (A)
1011 Touhy Ave.
Des Plaines, IL                  $  7,618     $ 1,374       Dec-93         (A)
1660 Feehanville Dr.
Mount Prospect, IL               $  6,019     $   706       Aug-95         (A)
175 Hawthorn Pkwy.
Vernon Hills, IL                 $  7,534     $ 1,407       Sep-94         (A)
Two Marriott Dr.
Lincolnshire, IL                 $  3,017     $   196       Jul-96         (A)
3400 Dundee Rd.
Northbrook, IL                   $  4,996     $   901       Oct-93         (A)
3010 & 3020 Wood Creek Dr.
Downers Grove, IL                $  9,815     $   620       Nov-96         (A)
823 Commerce Dr.
Oak Brook, IL                    $  5,026     $   934       Nov-95         (A)
3030 Warrenville Rd.
Lisle, IL                        $ 18,410     $   512       Sep-98         (A)
191 Waukegan Rd.
Northfield, IL                   $  4,772     $   109       Sep-98         (A)
11270 W. Park Place
Milwaukee, WI                    $ 16,399     $ 1,863       Sep-95         (A)
11925 W. Lake Park Dr.
Milwaukee, WI                    $  2,379     $   446       Jun-93         (A)
2514 S. 102nd St. &
10150 W. National Ave.
West Allis, WI                   $  8,675     $   731       Nov-96         (A)
150, 175, 250 Patrick Blvd.
Brookfield, WI                   $  7,282     $   975       Jun-94         (A)
375 Bishop's Way
Brookfield, WI                   $  5,313     $   339       Apr-97         (A)
111 East Kilbourn Ave.
Milwaukee, WI                    $ 48,697     $ 2,020       Apr-98         (A)
N17 W24222 Riverwood Dr.
Pewaukee, WI                     $  9,236     $    15       Dec-99         (A)
2550 University Ave. West
St. Paul, MN                     $ 24,549     $ 1,443       Dec-96         (A)
2221 University Ave. SE
Minneapolis, MN                  $  8,360     $   840       May-95         (A)
777 East Eisenhower Pkwy.
Ann Arbor, MI                    $ 22,551     $   781       Dec-97         (A)
32255 Northwestern Highway
Farmington Hills, MI             $ 26,044     $ 1,324       Dec-97         (A)
1301 W. Long Lake Rd.
Troy, MI                         $ 17,260     $ 1,497       Nov-96         (A)
No. 40 OakHollow
Southfield, MI                   $  7,779     $   611       Dec-96         (A)
24800 Denso Dr.
Southfield, MI                   $  6,829     $ 1,044       Aug-95         (A)
305, 315, 325 E. Eisenhower
Pkwy.
Ann Arbor, MI                    $ 19,887     $   274       May-99         (A)
655 Metro Place South
Dublin, OH                       $ 20,698     $ 1,308       Sep-97         (A)
4860-5000 Blazer Memorial Pkwy.
Dublin, OH                       $  9,028     $   639       Sep-96         (A)
425 Metro Place North
Dublin, OH                       $  7,948     $   518       Sep-97         (A)
175 South Third St.
Columbus, OH                     $ 22,627     $ 1,145       Jan-98         (A)
30 Merchant St.
Springdale, OH                   $  7,294     $ 1,238       Apr-96         (A)
116 Inverness Dr. East
Englewood, CO                    $ 21,531     $   808       May-98         (A)
183 Inverness Dr. West
Englewood, CO                    $ 20,362     $   664       May-98         (A)
                                 --------     -------
Totals.........................  $470,949     $32,772
                                 ========     =======
</TABLE>

------------------------
(A) Depreciation of buildings is computed over approximately a 40 year life on a
    straight-line basis. Tenant improvements are depreciated over the shorter of
    the estimated useful life of the improvements or the term of the lease.

(B) These properties are pledged as security for a mortgage loan with an
    outstanding principal amount of $73,180 at December 31, 1999.

(C) At December 31, 1999, the aggregate cost of land, buildings and improvements
    for Federal income tax purposes was approximately $461,572.

                                      S-1
<PAGE>
    Real Estate Owned:

<TABLE>
<CAPTION>
                                                            1999       1998       1997
                                                          --------   --------   --------
<S>                                                       <C>        <C>        <C>
  Balance beginning of year.............................  $448,557   $297,010   $189,114
  Property acquisitions.................................    28,600    142,245    102,283
  Additions.............................................    11,978     11,341      5,613
  Disposals.............................................    18,186      2,039
                                                          --------   --------   --------
  Balance end of year...................................  $470,949   $448,557   $297,010
                                                          ========   ========   ========
</TABLE>

    Accumulated Depreciation:

<TABLE>
<CAPTION>
                                                            1999       1998       1997
                                                          --------   --------   --------
<S>                                                       <C>        <C>        <C>
  Balance beginning of year.............................  $ 21,951   $ 11,314   $  5,240
  Depreciation expense..................................    13,799     11,371      6,074
  Disposals.............................................     2,978        734
                                                          --------   --------   --------
  Balance end of year...................................  $ 32,772   $ 21,951   $ 11,314
                                                          ========   ========   ========
</TABLE>

                                      S-2
<PAGE>
                                   SIGNATURES

    Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the registrant has duly caused this Amendment No. 1 to the
Annual Report on Form 10-K to be signed on its behalf by the undersigned,
thereunto duly authorized, on April 5, 2000.

<TABLE>
<S>                                                    <C>  <C>
                                                       GREAT LAKES REIT

                                                       By:            /s/ RICHARD L. RASLEY
                                                            -----------------------------------------
                                                                        Richard L. Rasley
                                                                    EXECUTIVE VICE PRESIDENT,
                                                                  SECRETARY AND GENERAL COUNSEL
</TABLE>

    Pursuant to the requirements of the Securities Exchange Act of 1934, this
report has been signed below by the following persons on behalf of the
registrant and in the capacities indicated on April 5, 2000.

<TABLE>
<CAPTION>
                                                                           TITLE
                                                       ----------------------------------------------
<C>                                                    <S>
                          *                            Chairman of the Board of Trustees and Chief
     -------------------------------------------         Executive Officer (Principal Executive
                   Richard A. May                        Officer)

                          *
     -------------------------------------------       President, Chief Operating Officer and Trustee
                   Patrick R. Hunt

                          *                            Chief Financial Officer and Treasurer
     -------------------------------------------         (Principal Financial Officer and Principal
                     James Hicks                         Accounting Officer)

                          *
     -------------------------------------------       Trustee
                James J. Brinkerhoff

                          *
     -------------------------------------------       Trustee
                  Daniel E. Josephs

                          *
     -------------------------------------------       Trustee
                  Daniel P. Kearney

                          *
     -------------------------------------------       Trustee
                  Edward Lowenthal

                          *
     -------------------------------------------       Trustee
                 Donald E. Phillips

* The undersigned by signing his name hereunto has hereby signed this Amendment No. 1 to Annual
  Report on Form 10-K on behalf of the above-named trustees and officers, on April 5, 2000, pursuant
  to a power of attorney executed by each such officer and trustee and previously filed with the
  Securities and Exchange Commission.
</TABLE>

<TABLE>
<S>                                                    <C>  <C>
                                                       By:            /s/ RICHARD L. RASLEY
                                                            -----------------------------------------
                                                                        Richard L. Rasley
</TABLE>