<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549
                                   FORM 10-K

[x]        ANNUAL REPORT PURSUANT TO SECTION 13 or 15(d) OF THE SECURITIES 
   EXCHANGE ACT OF 1934 (Fee Required)

                  For the fiscal year ended December 31, 1998
                                       OR
[ ]        TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES 
   EXCHANGE ACT OF 1934 (No Fee Required)

For the transition period from______________to____________

                         Commission File Number 0-15137

                                 MASSBANK Corp.
             (Exact name of registrant as specified in its charter)

              Delaware                                    04-2930382
    (State or other jurisdiction of                    (I.R.S. Employer
     incorporation or organization)                   Identification No.)

           123 HAVEN STREET
        Reading, Massachusetts                              01867
(Address of principal executive offices)                 (Zip Code)

       Registrant's telephone number, including area code: (617) 662-0100

          Securities registered pursuant to Section 12(b) of the Act:
                                      None

          Securities registered pursuant to Section 12(g) of the Act:
                    Common Stock, par value $1.00 per share
                                (Title of Class)

     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.____

     The aggregate market value of the voting stock held by non-affiliates of
the registrant, based on the closing price for the registrant's common stock on
March 19, 1999 as reported by NASDAQ, was $121,235,560.

     As of March 19, 1999, there were 3,455,959 shares of the registrant's
common stock outstanding.

                      DOCUMENTS INCORPORATED BY REFERENCE
     Portions of the registrant's 1998 Annual Report to Stockholders are
incorporated by reference in Parts I, II, III and IV of this Form 10-K. Portions
of the Proxy Statement for the 1999 Annual Meeting of Stockholders are
incorporated by reference in Part III of this Form 10-K.


<PAGE>   2

Cautionary Statement.

     Certain statements contained in this report or incorporated herein by
reference are "forward-looking statements." We may also make written or oral
forward-looking statements in other documents we file with the SEC, in our
annual reports to stockholders, in press releases and other written materials,
and in oral statements made by our officers, directors or employees. You can
identify forward-looking statements by the use of the words "believe," "expect,"
"anticipate," "intend," "estimate," "assume" and other similar expressions which
predict or indicate future events and trends and which do not relate to
historical matters. In addition, information concerning the costs, timing and
effectiveness of Year 2000 compliance, are forward-looking statements. You
should not rely on forward-looking statements, because they involve known and
unknown risks, uncertainties and other factors, some of which are beyond the
control of the Company. These risks, uncertainties and other factors may cause
the actual results, performance or achievements of the Company to be materially
different from the anticipated future results, performance or achievements
expressed or implied by the forward-looking statements.

     Some of the factors that might cause these differences include the
following: fluctuations in interest rates, price volatility in the stock and
bond markets, inflation, government regulations and economic conditions and
competition in the geographic and business areas in which the Company conducts
its operations; and the Company and its customers and suppliers may experience
unanticipated delays or expenses in achieving Year 2000 compliance. You should
carefully review all of these factors, and you should be aware that there may be
other factors that could cause these differences. These forward-looking
statements were based on information, plans and estimates at the date of this
report, and we do not promise to update any forward-looking statements to
reflect changes in underlying assumptions or factors, new information, future
events or other changes.


PART I

Item 1.  Business
                           Business of MASSBANK Corp.

General
     MASSBANK Corp. (the "Company") is a general business corporation
incorporated under the laws of the State of Delaware on August 11, 1986.
MASSBANK Corp. was organized for the purpose of becoming the holding company for
MASSBANK (the "Bank"). The Company is a one-bank holding company registered with
the Federal Reserve Board under the Bank Holding Company Act of 1956, as
amended. As of and since December 2, 1986, the effective date of the
reorganization whereby MASSBANK Corp. became the holding company for the Bank,
the Bank has been a wholly-owned subsidiary of MASSBANK Corp. The only office of
MASSBANK Corp., and its principal place of business, is located at the main
office of the Bank at 123 Haven Street, Reading, Massachusetts 01867.

     MASSBANK Corp. currently has no material assets other than its investment
in the Bank. The Company's primary business, therefore, is managing its
investment in the stock of the Bank. MASSBANK Corp. is classified by the
Commonwealth of Massachusetts as a securities corporation for tax purposes which
restricts its business to buying, selling, dealing in, or holding securities on
its own behalf. In the future, MASSBANK Corp. may become an operating company or
acquire banks or companies engaged in bank-related activities.


                                       2
<PAGE>   3

     MASSBANK Corp.'s principal sources of revenues on an unconsolidated basis
are dividends from the Bank and, to a lesser extent, interest income received
from its interest-bearing bank deposits. These revenues are used primarily for
the payment of dividends to stockholders and for the repurchase of Company
stock. MASSBANK Corp.'s assets on an unconsolidated basis at December 31, 1998
were represented by its investment in the Bank of $108.7 million and other
assets of $2.4 million. The Company's liabilities consisted of loan indebtedness
of $0.6 million and other liabilities of less than $0.1 million. The proceeds of
the loan were used to fund stock purchases through the Employee Stock Ownership
Plan ("ESOP"). See Note 17 to the Consolidated Financial Statements for parent
company only financial information. At December 31, 1998 MASSBANK Corp. on a
consolidated basis had total assets of $946.6 million, deposits of $824.0
million, and stockholders' equity of $110.5 million which represents 11.7% of
total assets. Book value per share at December 31, 1998 was $31.58.

     The Company does not own or lease any real or personal property. Instead it
intends to utilize during the immediate future the premises, equipment and
furniture of the Bank without the direct payment of rental fees to the Bank.

Competition
     The primary business of MASSBANK Corp. currently is the ongoing business of
the Bank. Therefore, the competitive conditions faced by MASSBANK Corp.
currently are the same as those faced by the Bank. See "Business of MASSBANK -
Competition." In addition, many banks and financial institutions have formed
holding companies. It is likely that these holding companies will attempt to
acquire commercial banks, thrift institutions or companies engaged in
bank-related activities. MASSBANK Corp. would face competition in undertaking
any such acquisitions and in operating any such entity subsequent to its
acquisition.

Employees
     MASSBANK Corp. does not employ any persons; its management also serves as
management of, and is paid by, the Bank. See "Item 10 - Directors and Executive
Officers of the Registrant." MASSBANK Corp. utilizes the support staff of the
Bank from time to time and does not pay any separate salaries or expenses in
connection therewith.

Dividends
     MASSBANK Corp. paid total cash dividends of $1.02 per share in 1998
compared to $0.885 per share in 1997 and $0.69 per share in 1996. The Company's
dividend payout ratios (cash dividends paid divided by net income) for 1998,
1997 and 1996 were 33%, 31% and 26%, respectively.

Stock Repurchase Program
     In January 1999, the Board of Directors re-authorized the Company's stock
repurchase program and added an additional 100,000 shares to the shares of the
Company's common stock authorized for repurchase in July 1997. During 1998, the
Company repurchased 119,200 of its common shares under its ongoing repurchase
program. This leaves 152,198 shares available for repurchase in the current
program.


                                       3
<PAGE>   4

Preferred Stock Purchase Rights
     In January 1990, the Board of Directors declared a dividend distribution of
one Preferred Stock Purchase Right for each outstanding share of MASSBANK Corp.
common stock. These Rights, which expire in January 2000, entitle their holders
to purchase from the Company one one-hundredth of a share (a "unit") of Series A
Junior Participating Cumulative Preferred Stock, par value $1.00 per share
("preferred stock") at a cash exercise price of $70.00 per unit, subject to
adjustment. The Rights will trade separately from the common stock and will
become exercisable when a person or group has acquired 15% or more of the
outstanding common stock, upon a tender offer that would result in a person or
group acquiring 15% or more of the outstanding common stock, or upon the
declaration by the Board of Directors that any person holding 10% or more of the
outstanding shares of common stock is an "adverse person".

     In the event a person or group acquires 15% or more of the outstanding
common stock or the Board of Directors declares a person an "adverse person",
each Right would entitle its holder (except if the holder is a person or group
described above) to receive upon exercise sufficient units of preferred stock to
equal a value of two times the exercise price of the Right. In the event the
Company is acquired in a merger or other business combination transaction or if
50% or more of the Company's assets or earning power is sold, each holder may
receive upon exercise common stock of the acquiring company having a market
value equal to two times the exercise price of the Right.

     The Rights are redeemable in whole, but not in part, by the Board of
Directors at a price of $.01 per Right any time before a person or group
acquires 15% or more of the outstanding common stock or the Board of Directors
declares a person an "adverse person".


                                       4
<PAGE>   5

                              Business of MASSBANK

General
     MASSBANK is a Massachusetts-chartered savings bank founded in 1872 as the
Melrose Savings Bank. In 1983, the Reading Savings Bank was merged into the
Melrose Savings Bank and the name of the resulting institution was changed to
MASSBANK for Savings. In 1986, the Bank converted from mutual to stock form of
ownership. In 1996, the name of the bank was changed from "MASSBANK for Savings"
to "MASSBANK".

     The Bank is primarily engaged in the business of attracting deposits from
the general public through its fifteen full service banking offices in Reading,
Chelmsford, Dracut, Everett, Lowell, Medford, Melrose, Stoneham, Tewksbury,
Westford and Wilmington, and originating residential and commercial real estate
mortgages, construction, and a variety of consumer loans. The Bank also invests
a significant portion of its funds in U.S. Treasury and Government agency
securities, mortgage-backed securities, federal funds sold, and other authorized
investments. The Bank's earnings depend largely upon net interest income, which
is the difference between the interest and dividend income derived by the Bank
from its loans and investments and the interest paid by the Bank on its deposits
and borrowed funds. The Company's earnings results are also affected by the
provision for loan losses; non-interest income, such as fee-based revenues and
net securities gains; non-interest expense; and income taxes.

     The Bank's deposits are insured to applicable limits by the Bank Insurance
Fund ("BIF") of the Federal Deposit Insurance Corporation (the "FDIC") and
excess deposit accounts are insured by the Depositors Insurance Fund ("DIF"), a
private industry-sponsored deposit insurer.

     The Bank recognizes that loan and investment opportunities change over time
and that yields derived from such opportunities can vary significantly even when
the risks associated with those opportunities are comparable. By developing a
relatively liquid loan and investment portfolio, the Bank has attempted to
position itself so as to be able to take advantage of these changing
opportunities. Consequently, the Bank expects that the relative mix of its loan
and investment portfolios will change over time in response to changing market
conditions.


                                       5
<PAGE>   6

Market Area
     The Bank is headquartered in Reading, Massachusetts, which is located
approximately 15 miles north of Boston. The Bank's market area includes a
significant portion of eastern Massachusetts and is served by a network of 15
branch offices located on a broad arc stretching from Melrose and Everett in the
south, Dracut in the north, and Westford in the west.

     The Bank's general market area consists of the municipalities in which it
operates banking offices and all of the contiguous cities and towns.

     The Bank currently operates banking offices in the municipalities of
Chelmsford, Dracut, Everett, Lowell, Medford, Melrose, Reading, Stoneham,
Tewksbury, Westford and Wilmington.

Lending Activities
     The Bank's net loan portfolio totaled $302.5 million at December 31, 1998.

The following table sets forth information concerning the Bank's loan portfolio
by type of loan at the dates shown:

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------------
(In thousands) At December 31,            1998       1997       1996       1995       1994
-------------------------------------------------------------------------------------------
Mortgage loans:
  Residential:
<S>                                   <C>        <C>        <C>        <C>        <C>     
    Conventional                      $280,681   $243,482   $216,832   $209,408   $207,772
    FHA and VA                           1,181      1,843      2,515      3,244      4,158
  Commercial                             2,257      3,861      4,121      6,975      8,155
  Construction                             730        492      1,388      1,516        603
-------------------------------------------------------------------------------------------
      Total mortgage loans             284,849    249,678    224,856    221,143    220,688
  Add: premium on loans                    259        343        325        388        452
  Less: deferred mortgage loan
         origination fees               (1,454)    (1,223)    (1,042)      (928)      (871)
-------------------------------------------------------------------------------------------
      Mortgage loans, net              283,654    248,798    224,139    220,603    220,269
-------------------------------------------------------------------------------------------
Other loans:
  Consumer:
    Installment                          1,547      2,199      1,967      1,988      1,972
    Guaranteed education                 7,967      8,934      9,729     10,420     10,152
    Other secured                        1,366      1,600      1,611      2,012      2,598
    Home equity lines of credit         10,159     10,470     11,316     13,144     14,674
    Unsecured                              235        266        271        265        269
-------------------------------------------------------------------------------------------
      Total consumer loans              21,274     23,469     24,894     27,829     29,665
  Commercial                                61         36        628        753        882
-------------------------------------------------------------------------------------------
      Total other loans                 21,335     23,505     25,522     28,582     30,547
-------------------------------------------------------------------------------------------
      Total loans                      304,989    272,303    249,661    249,185    250,816
Less:  Allowance for loan losses        (2,450)    (2,334)    (2,237)    (2,529)    (2,566)
-------------------------------------------------------------------------------------------
      Net loans                       $302,539   $269,969   $247,424   $246,656   $248,250
-------------------------------------------------------------------------------------------
</TABLE>


                                       6
<PAGE>   7

     The following table shows the maturity distribution and interest rate
sensitivity of the Bank's loan portfolio at December 31, 1998:

<TABLE>
<CAPTION>
                                             Maturity/Scheduled Payments (1)

                                Within       One to      Five to       After
(In thousands)                 one year    five years   ten years    ten years       Total
-------------------------------------------------------------------------------------------
Mortgage loans:
<S>                              <C>         <C>          <C>         <C>          <C>     
  Residential                    $  430      $10,168      $73,860     $196,227     $280,685
  Commercial & construction         368          234        1,166        1,201        2,969
-------------------------------------------------------------------------------------------
    Total mortgage loans            798       10,402       75,026      197,428      283,654
Other loans                       1,536        2,942        5,477       11,380       21,335
-------------------------------------------------------------------------------------------
    Total loans                  $2,334      $13,344      $80,503     $208,808     $304,989
-------------------------------------------------------------------------------------------
</TABLE>

(1) Loan amounts are accumulated as if the entire balance came due on the last
contractual payment date. Accordingly, the amounts do not reflect proceeds from
contractual loan amortization or anticipated prepayments.


     The following table shows the amounts, included in the table above, which
are due after one year and which have fixed or adjustable interest rates:

<TABLE>
<CAPTION>
                                                     Total Due After One Year

                                                    Fixed           Adjustable
(In thousands)                                      Rate              Rate          Total
-------------------------------------------------------------------------------------------
Mortgage loans:
<S>                                                <C>               <C>           <C>     
  Residential                                      $237,657          $42,598       $280,255
  Commercial & construction                             671            1,930          2,601
-------------------------------------------------------------------------------------------
    Total mortgage loans                            238,328           44,528        282,856
Other loans                                           1,681           18,118         19,799
-------------------------------------------------------------------------------------------
    Total loans                                    $240,009          $62,646       $302,655
-------------------------------------------------------------------------------------------
</TABLE>

     Mortgage Lending. The Bank believes that the repayment periods of long-term
first mortgage loans, the general resistance of the public to variable rate
mortgage instruments and the highly competitive nature of the mortgage industry
require a prudent approach to mortgage lending. Consequently, as part of its
policy of generally attempting to match the maturities of its assets and its
liabilities, the Bank, over several years, has kept its mortgage loan portfolio
to a level at which the Bank believed there was an acceptable risk-to-reward
ratio in light of opportunities in the marketplace and the Bank's long-term
objectives. The Bank's net loan portfolio represented approximately 32.0% and
29.2% of the Company's total assets at December 31, 1998, and 1997,
respectively. The Bank realizes that this low level of loans with respect to
assets in relation to the securities portfolio results in a reduction in yield;
however, the Bank believes that this reduction would be more than offset in risk
and loss associated with lending during periods of economic decline. In today's
economic climate, the Bank would prefer a more even mix of loans and securities.
However, there remains a tremendous amount of competition for mortgages in the
Bank's area, and developing a quality loan portfolio takes time. The Bank
anticipates that its loan portfolio will grow slowly over the next few years.


                                       7
<PAGE>   8

Mortgage Lending (continued)

     Loan originations come from a number of sources, including referrals from
real estate brokers, walk-in customers, purchasers of property owned by existing
customers and refinancing for existing customers. In addition to actively
soliciting loan referrals, the Bank conducts an advertising and promotion
program, directed both toward the general public and real estate professionals
who might refer potential borrowers.

     Substantially all of the real estate loans originated by the Bank during
1998 were secured by real estate located in the Bank's primary lending area,
reflecting the Bank's commitment to serve the credit needs of the local
communities in which it operates banking offices.

     The Bank makes both conventional fixed and adjustable-rate loans on
one-to-four family residential properties for a term of ten to thirty years. The
Bank currently retains all of the mortgages it originates for its own portfolio.
These are primarily 10, 12, 15 or 20 year fixed rate mortgages and adjustable
rate mortgages. The few long-term (25 or 30 year) fixed rate mortgages the bank
originated in 1998 were added to the bank's loan portfolio. However, in prior
years, these mortgages were generally sold in the secondary market. Adjustable
rate mortgage loans ("ARMs") have rates that are re-set at either 1, 3, 5 or 10
year intervals and provide a margin over various mortgage indices.

     The Bank also has a Home Equity Line of Credit product which it hopes will
generate new business in the coming year. This product, which was introduced in
1997, offers customers a special introductory interest rate of 7.25% which is
fixed until the year 2000. Thereafter, the interest rate will be variable and
will be indexed to the 13 week (91 day) Treasury Bill auction rate plus a margin
of 3.25%. This indexed variable rate has historically responded more favorably
to movements in market interest rates than the PRIME RATE used by many financial
institutions and should, therefore, be more attractive to bank customers.

     In recent years, the Bank has instituted several other new loan programs
which have been well received by customers. It instituted a program featuring a
5/1 and 7/1 year ARM product with an initial fixed rate for 5 or 7 years and a 1
year adjustable rate thereafter. A special First Time Home Buyers Program has
also been instituted featuring a discounted 7/1 ARM. This program is designed
for first-time home buyers meeting certain income and property location
restrictions. The Bank has also introduced the "Home Town Advantage" mortgage
program which has produced some good results. This program offers homebuyers a
(0.125) percent discount on their mortgage rate if they purchase residential
property located in one of the communities where the bank operates a banking
office.

     At December 31, 1998, 1-4 family residential mortgage loans totaled $280.7
million, or 92.0% of the total loan portfolio, compared to $244.5 million, or
89.8% of the total loan portfolio, at December 31, 1997. Residential mortgage
loan originations amounted to $95.7 million during 1998, an increase of 91.4%
from $50.0 million in 1997. Origination volumes are sensitive to interest rates
and are affected by the interest rate environment. The prevailing low interest
rates in 1998 encouraged many borrowers to refinance. This resulted in higher
mortgage loan originations for the Bank.

     The Bank also originates mortgage loans secured by commercial or investment
property such as multifamily housing, strip shopping centers, office buildings
and retail buildings. At December 31, 1998, commercial and multifamily real
estate mortgages and construction loans totaled approximately $3.0 million, or
1.0% of the total loan portfolio, compared to $4.3 million, or 1.6% of the total
loan portfolio, at December 31, 1997. In 1998, commercial and multifamily real
estate mortgage loan originations amounted to $0.2 million.


                                       8
<PAGE>   9

Mortgage Lending (continued)

     The total amount of first mortgage loans held by the Bank at December 31,
1998 was $283.7 million as indicated in the maturity distribution table
appearing on page six. Of this amount, $44.9 million was subject to interest
rate adjustments. The remaining $238.8 million in fixed rate mortgage loans
represents 25.2% of the Company's total assets.

     Fees received for originating loans and related direct incremental loan
origination costs are offset and the resulting net amount is deferred and
amortized over the life of the related loans using the level-yield method.

     The Bank also receives fees and charges relating to existing loans,
primarily late charges and prepayment penalties.

     Other Loans. The Bank makes a variety of consumer loans and had a consumer
loan portfolio of approximately $21.3 million at December 31, 1998 representing
7.0% of the Bank's total loan portfolio. Of this amount $8.0 million or 2.6% of
the total loan portfolio are education loans made under the Massachusetts Higher
Education Assistance Corporation. The Bank may sell education loans in the
future.

     The balance of the Bank's consumer loan portfolio consists of home equity
lines of credit and installment consumer credit contracts such as automobile
loans, home improvement loans and other secured and unsecured financings. These
loans totaled $13.3 million at December 31, 1998, representing 4.4% of the
Bank's total loan portfolio.

     At December 31, 1998, the Bank had only $61 thousand in outstanding loans
to commercial enterprises not secured by real estate.

     Loan Approval. The Bank's loan approval process for all loans generally
includes a review of an applicant's financial statements, credit history,
banking history and verification of employment. For mortgage loans, the Bank
generally obtains an independent appraisal of the subject property. The Bank has
a formal lending policy approved by the Board of Directors of the Bank which
delegates levels of loan approval authority to Bank personnel. All loans in
excess of established limits require approval of the Bank's Board of Directors.

     The Bank issues commitments to prospective borrowers to make loans subject
to certain conditions for generally up to 60 days. The interest rate applicable
to the committed loans is usually the rate in effect at the time the application
fee is paid. At December 31, 1998, the Bank had issued commitments on
residential first mortgage loans totaling $7,941,000, and had commitments to
advance funds on construction loans and unused credit lines, including unused
portions of home equity lines of credit, of $281,000 and $29,163,000,
respectively.

     Loan Delinquencies. It is the Bank's policy to manage its loan portfolio so
as to recognize problem loans at an early stage and thereby minimize loan
losses. Loans are considered delinquent when any payment of principal or
interest is 30 days or more past due. The Bank generally commences collection
procedures, however, when accounts are 15 days past due. It is the Bank's
practice to generally discontinue accrual of interest on all loans for which
payments are more than 90 days past due. Loans delinquent for 90 or more days,
as shown in the table on the following page, totaled $1,004,000 at December 31,
1998.


                                       9
<PAGE>   10

Real Estate Acquired through Foreclosure.
     Real estate acquired through foreclosure is comprised of foreclosed
properties where the Bank has actually received title and loans determined to be
substantially repossessed. Real estate loans that are substantially repossessed
include only those loans for which the Bank has taken possession of the
collateral but has not completed legal foreclosure proceedings. Loan losses
arising from the acquisition of such properties are charged against the
allowance for loan losses. Real estate acquired through foreclosure is recorded
at the lower of the carrying value of the loan or the fair value of the property
constructively or actually received, less estimated costs to sell the property
following foreclosure. Operating expenses and any subsequent provisions to
reduce the carrying value to fair value are charged to current period earnings.
Gains and losses upon disposition are reflected in earnings as realized. As of
year-end 1998, MASSBANK had $86 thousand in real estate acquired through
foreclosure on its balance sheet.


Non-Performing Assets

     The following table shows the composition of non-performing assets at the
dates shown:

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------
(In thousands) At December 31,                     1998      1997      1996      1995      1994
------------------------------------------------------------------------------------------------
<S>                                              <C>       <C>       <C>       <C>       <C>   
Nonaccrual loans:
  Mortgage loans:
    Residential:
      Conventional                               $  845    $1,536    $1,468    $2,016    $1,496
      FHA and VA                                     --         9        13        14        62
    Commercial                                       --        --        --        --       152
  Consumer                                          159       226       120       398       388
------------------------------------------------------------------------------------------------
    Total nonaccrual loans                        1,004     1,771     1,601     2,428     2,098
------------------------------------------------------------------------------------------------
Real estate acquired through foreclosure:
  Residential:
    Conventional                                     86        --       503       255       129
------------------------------------------------------------------------------------------------
    Total real estate acquired through
     foreclosure                                     86        --       503       255       129
------------------------------------------------------------------------------------------------
     Total non-performing assets                 $1,090    $1,771    $2,104    $2,683    $2,227
------------------------------------------------------------------------------------------------
Percent of non-performing loans to total loans     0.33%     0.65%     0.64%     0.97%     0.84%
Percent of non-performing assets to total assets   0.12%     0.19%     0.24%     0.31%     0.26%
</TABLE>


     The reduction in interest income associated with nonaccrual loans is as
follows:
<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------

(In thousands) Years Ended December 31,            1998      1997      1996      1995     1994
------------------------------------------------------------------------------------------------
<S>                                                <C>       <C>       <C>       <C>       <C> 
  Interest income that would have been
    recorded under original terms                  $ 84      $163      $149      $204      $185
  Interest income actually recorded                  61        97        78        60        88
------------------------------------------------------------------------------------------------
  Reduction in interest income                     $ 23      $ 66      $ 71      $144      $ 97
------------------------------------------------------------------------------------------------
</TABLE>


                                       10
<PAGE>   11

Allowance for Loan Losses.
     The allowance for loan losses is increased by provisions charged to
operations based on management's assessment of many factors including the risk
characteristics of the portfolio, underlying collateral, current and anticipated
economic conditions that may affect the borrower's ability to pay, and trends in
loan delinquencies and charge-offs. Realized losses, net of recoveries, are
charged directly to the allowance. While management uses the information
available in establishing the allowance for loan losses, future adjustments to
the allowance may be necessary if economic conditions differ substantially from
the assumptions used in making the evaluation. In addition, various regulatory
agencies, as an integral part of their examination process, periodically review
the Bank's allowance for loan losses. Such agencies may require the Bank to
recognize additions to the allowance based on judgments different from those of
management.

The following table sets forth the activity in the allowance for loan losses
during the years indicated:



<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------
(In thousands) Years ended December 31,            1998      1997      1996      1995      1994
------------------------------------------------------------------------------------------------
<S>                                              <C>       <C>       <C>       <C>       <C>   
Balance at beginning of year                     $2,334    $2,237    $2,529    $2,566    $2,261
Glendale Co-Operative Bank acquisition               --       105        --        --        --
Provision for loan losses                           193       260       160       170       705

Charge-offs:
                   Residential real estate          (81)     (221)     (480)     (124)     (339)
                   Consumer loans                   (22)      (12)      (25)      (30)      (24)
                   Other loans                       --       (94)      (37)      (95)      (63)

Recoveries:
                   Residential real estate           17        34        83        41        23
                   Commercial real estate            --        20        --        --        --
                   Consumer loans                     6         1         7         1         3
                   Other Loans                        3         4        --        --        --
------------------------------------------------------------------------------------------------
Net charge-offs                                     (77)     (268)     (452)     (207)     (400)
------------------------------------------------------------------------------------------------
Balance at end of year                           $2,450    $2,334    $2,237    $2,529    $2,566
------------------------------------------------------------------------------------------------

Net loan charge offs as a percent of average
  loans outstanding during the period              0.03%     0.10%     0.18%     0.08%     0.16%
Allowance for loan losses as a percent
  of total loans outstanding at year-end           0.80%     0.86%     0.90%     1.01%     1.02%
Allowance for loan losses as a percent
  of nonaccrual loans                             244.0%    131.8%    139.7%    104.2%    122.3%

------------------------------------------------------------------------------------------------
</TABLE>


                                       11
<PAGE>   12

Investment Activities

      The Bank believes that investment opportunities in United States
Government, corporate and other securities are at times more attractive than the
opportunities present in the loan market. As compared to loans, these
investments of the Bank are generally shorter-term and hence more liquid, are
subject to lower risk of loss, and present an opportunity for appreciation. In
addition, these investments often permit the Bank to better match the maturities
of its assets and its liabilities.

     The Bank's investment portfolio is managed by its officers in accordance
with an investment policy approved by the Bank's Board of Directors. The
objectives of that policy are to provide a level of liquidity, earnings and
diversification consistent with the exercise of prudent investment judgment. The
policy authorizes the senior management of the Bank to make and execute
investment decisions and requires that those persons report all investment
transactions to the Bank's Board of Directors at each of its regular meetings.
In addition, management is required to report all gains or losses on all
securities transactions at each meeting of the Bank's Board of Directors.
Purchases and sales of securities by the Bank are generally required to be made
on a competitive basis and all investments must be permitted by applicable law.

     The Bank invests in a wide variety of securities and obligations,
including: Federal funds sold (which are sold only to institutions included on
the Bank's internally-prepared approved list of adequately capitalized
institutions); commercial paper and bankers' acceptances; United States Treasury
and Government agency obligations; United States agency guaranteed and other
mortgage-backed securities; investment grade corporate debt securities
(generally limited to those rated A or better by Standard & Poor's); mutual
funds; and equity securities traded on a national securities exchange or quoted
on the NASDAQ System.

     Under the investment policy management determines the appropriate
classification of securities at the time of purchase. Those securities that the
Company has the intent and the ability to hold to maturity are classified as
securities held to maturity and are carried at amortized historical cost.

     Those securities held for indefinite periods of time and not intended to be
held to maturity are classified as available for sale. Securities held for
indefinite periods of time include securities that management intends to use as
part of its asset/liability management strategy and that may be sold in response
to changes in interest rates, changes in prepayment risk, the need to increase
regulatory capital and other similar factors. Income on debt securities
available for sale is accrued and included in interest and dividend income. The
specific identification method is used to determine realized gains and losses on
sales of securities available for sale which are also reported in non-interest
income under the caption "gains on securities." When a security suffers a loss
in value which is considered other than temporary, such loss is recognized by a
charge to earnings.


                                       12
<PAGE>   13

Investment Activities (continued)

     Investments classified as trading securities are stated at market with
unrealized gains or losses included in earnings. Income on debt trading
securities is accrued and included in interest and dividend income. All of the
Company's mortgage-backed securities are currently classified as available for
sale. At times of low loan demand, short-term mortgage-backed securities may be
used as substitutes for loans as certain of their financial characteristics are
very similar to short-term mortgage loans.

     At December 31, 1998, the Company's investments, which consists of
securities held to maturity, securities available for sale (including
mortgage-backed securities), trading securities, short-term investments, term
federal funds sold and interest-bearing deposits in banks totaled $624.1
million, representing 65.9% of the Company's total assets.


                                       13
<PAGE>   14

     The following table sets forth the composition of the Company's investment
portfolio as of the dates indicated:

                              Investment Portfolio

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------
(In thousands) At December 31,                         1998             1997             1996
------------------------------------------------------------------------------------------------
<S>                                                <C>              <C>              <C>     
  Federal funds sold:
    Overnight federal funds                        $123,207         $ 85,241         $109,902
    Term federal funds                               25,000           20,000           10,000
------------------------------------------------------------------------------------------------
      Total federal funds sold                      148,207          105,241          119,902
  Money market funds                                 24,569           24,514           24,408
  Interest-bearing deposits in bank                   2,033            2,083            1,751
------------------------------------------------------------------------------------------------
      Total federal funds sold and other
        short-term investments                     $174,809         $131,838         $146,061
------------------------------------------------------------------------------------------------
      Percent of total assets                          18.5%            14.2%            16.4%
------------------------------------------------------------------------------------------------

(In thousands) At December 31,                         1998             1997             1996
------------------------------------------------------------------------------------------------
Securities held to maturity: (a)
    Other bonds and obligations                    $    354         $    372         $    160
------------------------------------------------------------------------------------------------
      Total securities held to maturity            $    354         $    372         $    160

Securities available for sale: (b)
    U.S. Treasury obligations                       114,981          123,021          140,706
    U.S. Government agency obligations                8,992            9,813            7,877
    Other bonds and obligations                          --               --            1,000
    Marketable equity securities                     21,580           17,545           15,574
    Investments in mutual funds                          --            1,114               --
    Mortgage-backed securities                      272,573          330,731          306,595
------------------------------------------------------------------------------------------------
      Total securities available for sale           418,126          482,224          471,752

Trading securities: (b)
    U.S. Treasury obligations                        29,707           18,542               --
    Investments in mutual funds                       1,086            2,718            4,672
------------------------------------------------------------------------------------------------
      Total trading securities                       30,793           21,260            4,672
------------------------------------------------------------------------------------------------
      Total securities                             $449,273         $503,856         $476,584
------------------------------------------------------------------------------------------------
      Percent of total assets                          47.5%            54.4%            53.7%
------------------------------------------------------------------------------------------------
Total investments                                  $624,082         $635,694         $622,645
Total investments as a percent of total assets         65.9%            68.7%            70.1%
------------------------------------------------------------------------------------------------
</TABLE>

(a)  At amortized cost.
(b)  At market value.


                                       14
<PAGE>   15

     The following tables present the carrying value of debt securities held to
maturity and available for sale at December 31, 1998 maturing within stated
periods with the weighted average interest yield from securities falling within
the range of maturities: 
                        Debt Securities Held to Maturity

<TABLE>
<CAPTION>
                                                           Other
                                                           bonds
                                                           and
(Dollars in thousands)                                     obligations (1)      Total
-----------------------------------------------------------------------------------------
<S>                                                        <C>                 <C>  
Maturing after 1 but within 5 years
  Amount                                                   $ 230               $ 230
  Yield                                                     6.79%               6.79%
Maturing after 5 years but within 10 years
  Amount                                                   $  82               $  82
  Yield                                                     9.07%               9.07%
Maturing after 10 years but within 15 years
  Amount                                                      42                  42
  Yield                                                     9.69%               9.69%
-----------------------------------------------------------------------------------------
Total
  Amount                                                   $ 354               $ 354
  Yield                                                     7.66%               7.66%

Average life in years                                       4.20                4.20
</TABLE>

                       Debt Securities Available for Sale

<TABLE>
<CAPTION>
                                                  U.S.            Mortgage-
                                   U. S.          Government      backed
                                   Treasury       agency          securities (2)
(Dollars in thousands)             obligations    obligations                        Total
------------------------------------------------------------------------------------------------
<S>                                <C>            <C>             <C>               <C>     
Maturing within 1 year
  Amount                           $ 50,876       $2,000          $    371          $ 53,247
  Yield                                6.24%        5.62%             4.50%             6.21%
Maturing after 1
but within 5 years
  Amount                             58,790        6,771             6,014            71,575
  Yield                                6.24%        5.99%             7.70%             6.34%
Maturing after 5
but within 10 years
  Amount                              2,961           --            35,087            38,048
  Yield                                5.85%          --              7.10%             7.00%
Maturing after 10
but within 15 years
  Amount                                 --           --           219,579           219,579
  Yield                                                               6.89%             6.89%
Maturing after 15 years
  Amount                                 --          195             4,645             4,840
  Yield                                             7.94%             6.07%             6.15%
------------------------------------------------------------------------------------------------
Total
  Amount                           $112,627       $8,966          $265,696          $387,289
  Yield                                6.23%        5.95%             6.89%             6.68%
------------------------------------------------------------------------------------------------
Average life in years                  1.51         2.90
Average contractual
 maturity in years                                                   11.67
</TABLE>


                                       15
<PAGE>   16

(1)  Yields on tax exempt obligations have been computed on a tax equivalent
     basis.

(2)  Mortgage-backed securities are shown at their contractual maturity, but are
     expected to have shorter lives due to scheduled payments and prepayments.

     At December 31, 1998, the Company did not have an investment in any issuer
(other than securities of the U.S. government) in excess of 10% of stockholders
equity.


                                       16
<PAGE>   17

Deposits and Other Sources of Funds

     General. Deposits have been the primary source of funds of the Bank for
making investments and loans. In addition to deposits, the Bank's other major
sources of funds are derived from amortization and prepayment of loans and
mortgage-backed securities, from sales or maturities of securities, and from
operations. Deposit flows can vary significantly and are influenced by
prevailing interest rates, money market conditions, economic conditions and
competition. The Bank can respond to changing market conditions and competition
through the pricing of its deposit accounts. Management can control the level of
its deposits to a significant degree through its pricing policies. Another
important factor in attracting deposits is convenience. In addition to the
Bank's fifteen conveniently located banking offices, customers can access
accounts through the Bank's ATM network. The Bank is a member of the Transaxion
("TX"), New York Cash Exchange ("NYCE") and CIRRUS System, Inc. ("CIRRUS")
networks which allow access to ATMs in over 100,000 locations worldwide.

     Deposits. A substantial amount of the Bank's deposits are derived from
customers who live or work within the Bank's market area. The Bank does not
solicit deposits through any outside agents. The Bank's deposits consist of
regular, silver and smart savings accounts, special notice accounts, NOW and
Super NOW accounts, business checking accounts, money market deposit accounts,
IRA and Keogh accounts, and term deposit accounts.

     The performance of the stock market in 1998, continued to draw savings from
bank deposit accounts making it more difficult to grow total bank deposits. As a
result, the Bank's deposits increased by $14.1 million or a modest 1.8% during
the twelve months ended December 31, 1998, from $809.9 million at year-end 1997
to $824.0 million at the end of 1998.

     Borrowed Funds. From time to time the Bank has obtained funds through
repurchase agreements with its customers and federal funds purchased. The Bank
also has the ability, although it has never exercised it, to borrow from the
Federal Reserve Bank and The Depositors Insurance Fund, Inc. The Company did not
have any borrowed funds in 1998 or 1997.


                                       17
<PAGE>   18

                                    DEPOSITS

     The following table shows the composition of the deposits as of the dates
indicated:

<TABLE>
<CAPTION>
(In thousands) at December 31,             1998                   1997               1996
------------------------------------------------------------------------------------------------
                                               Percent              Percent              Percent
                                                 of                   of                   of
                                     Amount   Deposits    Amount   Deposits    Amount   Deposits
<S>                                 <C>         <C>      <C>         <C>      <C>          <C>  
Demand and NOW
  NOW                               $ 52,324    6.35%    $ 47,944    5.92%    $ 45,352     5.75%
  Demand accounts
   (non interest-bearing)             23,849    2.89       18,915    2.34       17,382     2.21
                                      -------   ----       ------    -----      -------   -----
    Total demand and NOW              76,173    9.24       66,859    8.26       62,734     7.96

Savings:
  Regular savings and
    special notice accounts          326,192   39.59      329,348   40.67      333,834   42.35
  Money market accounts               21,857    2.65       23,527    2.90       23,824    3.02
                                     -------   -----      -------   -----      -------   -----
    Total savings                    348,049   42.24      352,875   43.57      357,658   45.37

Time Certificates of deposit:
  Fixed rate certificates            318,491   38.65      316,368   39.06      303,722   38.52
  Variable rate certificates          82,033    9.96       74,666    9.22       65,417    8.30
                                     -------   -----      -------   -----      -------   -----
    Total time certificates
      of deposit                     400,524   48.61      391,034   48.28      369,139   46.82

Deposit acquisition premium,
  net of amortization                   (715)   (.09)        (918)  (0.11)      (1,181)   (.15)
                                     -------   -----      -------   -----      -------    ----

    Total deposits                  $824,031  100.00%    $809,850  100.00%    $788,350  100.00%
</TABLE>


     In the following table the average amount of deposits and average rate is
shown for each of the years as indicated.


<TABLE>
<CAPTION>
(In thousands) Years Ended December 31,     1998                 1997                1996
------------------------------------------------------------------------------------------------

                                     Average   Average    Average   Average    Average   Average
                                     Balance    Rate      Balance     Rate     Balance     Rate

<S>                                 <C>         <C>      <C>         <C>      <C>         <C>  
NOW accounts                        $ 48,006    1.15%    $ 46,580    1.14%    $ 47,197    1.21%
Demand (non interest-bearing)
   accounts                           21,011      --       18,156      --       15,992      --
Escrow deposits of borrowers           1,142    0.18        1,159    0.28          780    0.19
Money market accounts                 22,299    3.07       24,186    3.07       25,205    3.20
Regular savings and
   special notice accounts           327,338    3.44      331,209    3.47      332,851    3.44
Time certificates of deposit         391,816    5.57      386,062    5.67      352,385    5.74
                                     -------              -------              -------
                                     811,612    4.23%     807,352    4.30%    $774,410    4.27%
</TABLE>


                                       18
<PAGE>   19

Investment Management and Trust Services

     The Bank's Trust and Investment Services Division offers a variety of
investment, trust and estate planning services and also serves as Trustee,
Executor, and Executor's Agent for bank customers.

     As of December 31, 1998 the Trust Division had approximately $31.7 million
(market value) of assets in custody and under management.

Competition

     The Bank faces substantial competition both in originating loans and in
attracting deposits. Competition in originating loans comes primarily from other
thrift institutions, commercial banks, credit unions and mortgage banking
companies. The Bank competes for loans principally on the basis of interest
rates and loan fees, the types of loans originated and the quality of services
provided to borrowers.

     In attracting deposits, the Bank's primary competitors are other thrift
institutions, commercial banks, mutual funds and credit unions located in its
market area. The Bank's attraction and retention of deposits depend on its
ability to provide investment opportunities that satisfy the requirements of
customers with respect to rate of return, liquidity, risk and other factors. The
Bank attracts a significant amount of deposits through its branch offices
primarily from the communities in which those branch offices are located. The
Bank competes for these deposits by offering competitive rates, convenient
branches and ATM locations and convenient business hours.


                                       19
<PAGE>   20

Supervision and Regulation of the Company and its Subsidiaries

     The Company and the Bank are in a heavily regulated industry. As a Delaware
business corporation, the Company is subject to all of the federal and state
laws and regulations that apply to corporations generally, including the federal
and state securities laws and the Delaware Business Corporation Law. In
addition, as a company that owns and controls a bank, the Company is regulated
as a bank holding company, is subject to supervision, examination and regulation
by the Board of Governors of the Federal Reserve System (the "FRB") under the
federal Bank Holding Company Act (the "BHC Act"), and is subject to statutes,
regulations and policies administered by the FRB relating to, among other
things, mergers, acquisitions and changes in controlling ownership, non-bank
activities and subsidiaries, capital adequacy, the receipt and payment of
dividends, and the provision of financial and managerial support to its
subsidiary bank. In addition, the Company is subject to certain state law
restrictions administered by the Massachusetts Division of Banks (the
"Division"), relating to, among other things, the acquisition of additional
banking institutions and the conduct of nonbank activities.

     As a Massachusetts-chartered savings bank whose deposits are insured by the
Federal Deposit Insurance Corporation (the "FDIC") (and, with respect to any
deposits in excess of FDIC limits, by the private, industry-sponsored Depositors
Insurance Fund of Massachusetts), the Bank is subject to regulation, supervision
and examination by federal and state regulatory authorities, including the FDIC
and the Division. This framework of federal and state banking supervision and
regulation is administered primarily for the benefit of borrowers, depositors
and the respective deposit insurance funds and not for the benefit of the Bank,
the Company or its stockholders.

     The Bank is subject to extensive federal and state statutes, regulations,
policies and standards regarding virtually all aspects of its operations,
including capital adequacy, reserves, liquidity, payment of dividends,
transactions with affiliates, loans to officers, directors, principal
shareholders and their related interests, mergers, acquisitions and changes in
controlling ownership, establishment, relocation and closure of branch banking
offices, community reinvestment, equal credit opportunity, credit reporting,
real estate settlement procedures, funds availability, disclosure to consumers,
financial accounting, reporting and recordkeeping, and Year 2000 preparedness.
In the event the Bank failed to maintain adequate capital or otherwise failed to
operate in accordance with applicable federal and Massachusetts statutes,
regulations or policies, the FDIC and the Division have authority to place the
Bank in receivership or conservatorship or impose other sanctions, including but
not limited to restrictions on dividend or other payments by the Bank to the
Company, termination of the Bank's deposit insurance, restrictions on the Bank's
growth, issuance of orders to cease and desist from or to take specified
actions, assessment of money penalties, and removal of officers or directors.

     The Federal Deposit Insurance Corporation Improvement Act of 1991
("FDICIA") establishes five categories of banking institutions -- in descending
order of capital adequacy: "well-capitalized," "adequately capitalized,"
"undercapitalized," significantly undercapitalized," and "critically
undercapitalized" -- and imposes certain restrictions and requires federal bank
regulatory agencies to take "prompt corrective action" with respect to banks
that are in one of the three "undercapitalized" categories. As of December 31,
1998, the Bank was "well capitalized" as defined under FDICIA. For a discussion
of the Bank's capital adequacy, see Note 14 to the Company's Consolidated
Financial Statements, on page 42.


                                       20
<PAGE>   21

     FDICIA establishes a system of risk-based deposit insurance assessments
that takes a bank's capital level and supervisory risk characteristics into
account in calculating the amount of its federal deposit insurance assessment.
In addition, FDICIA places certain restrictions on the equity investments and
other "principal" activities of all state-chartered banks, including the Bank.
FDICIA further requires the FDIC and other federal bank regulatory agencies to
establish regulatory "safety and soundness" standards to govern various aspects
of bank operations including internal controls, information systems and audit
systems, loan documentation, credit underwriting, interest rate risk exposure,
asset growth, executive compensation, asset quality, earnings and stock
valuation, as the agencies consider appropriate. The FDIC may require a bank
that is not in compliance with safety and soundness standards promulgated under
FDICIA to submit and implement a written plan to achieve compliance within a
specified time period and may impose sanctions on a bank that fails to submit
and implement an acceptable plan when required. At December 31, 1998, the Bank's
operations were in substantial compliance with all applicable safety and
soundness standards promulgated under FDICA.

     On September 29, 1994, the Riegle-Neal Interstate Banking and Branching Act
of 1994 (the "Interstate Banking Act") was signed into law by President Clinton.
In 1996, Massachusetts enacted legislation "opting in" to interstate branch
banking and imposing certain limitations and requirements as permitted by the
Interstate Banking Act. The Interstate Banking Act and the 1996 Massachusetts
legislation permit interstate branching, mergers and bank acquisitions by
Massachusetts bank holding companies and banks and permit out-of-state bank
holding companies and banks to expand their banking operations into
Massachusetts by merger, acquisition or de novo branching subject to certain
regulatory approval requirements and other limitations.

     From time to time, commencing in June, 1996, the federal bank regulatory
agencies jointly issued written statements of guidance (the "Year 2000
Guidance") to federally-insured banks on various aspects of the so-called "Y2K
Problem" -- the inability of certain computer components and software to
correctly process the millennium date change from 1999 to 2000. On October 15,
1998, the FDIC and the other federal banking agencies promulgated "Interagency
Guidelines Establishing Year 2000 Standards for Safety and Soundness" (the "Year
2000 Standards") under FDICIA. Early in 1999, the Division issued regulations
applicable to Massachusetts banks incorporating the federal Year 2000 Guidance
and Standards. Among other things, the Year 2000 Guidance and Standards require
all FDIC-insured banks to involve their management and board of directors in
their Year 2000 preparedness efforts, to adopt written project plans for Year
2000 preparedness, to "renovate" "mission critical" data processing systems, to
complete testing of renovated systems within specified time frames, to develop
contingency plans and to "manage customer-risk."

     Under FDICIA, the FDIC may require a bank that is not in compliance with
the Year 2000 Standards to submit and implement a written plan to achieve
compliance within a specified time period. In addition, substantial failure by a
bank to comply with the Year 2000 Guidance and Standards may provide a basis for
the FDIC or the Division to take other regulatory actions, including but not
limited to placing the bank in receivership, restricting the bank's dividend and
other payments to its parent company, terminating the Bank's federal deposit
insurance, and directing the bank to cease and desist from or to take specified
actions. At December 31, 1998, the Bank's Year 2000 preparedness efforts were
believed to be in substantial compliance with the Year 2000 Guidance and
Standards. For a discussion of the Company's Year 2000 preparedness efforts, see
"Management's Discussion and Analysis of Financial Condition and Results of
Operations -- Year 2000 Issue" at page 15.


                                       21
<PAGE>   22

     From time to time the U.S. Congress and the Massachusetts Legislature adopt
legislation and the Federal and State bank regulatory agencies issue regulations
and policies that may significantly affect the operations of the Bank and the
Company. No assurance can be given as to whether or when such additional
legislation, regulations or policies may be adopted or as to the effect any such
legislation, regulations or policies may have on the Company or the Bank.

Employees

     MASSBANK Corp. utilizes the support staff of the Bank from time to time
without the payment of any fees. No separate compensation is being paid to the
executive officers of MASSBANK Corp., all of whom are executive officers of the
Bank and receive compensation as such. As of December 31, 1998, the Bank had 141
full-time employees, including 31 officers, and 66 part-time employees. None of
the Bank's employees is represented by a collective bargaining group, and
management believes that its employee relations are good. The Bank provides its
employees with formal training in product knowledge, sales techniques, fair
lending, and motivation. In addition, each supervisor at the Bank receives
management training before assuming his or her supervisory duties and
periodically thereafter. The Bank maintains a comprehensive employee benefit
program for qualified employees that includes a qualified pension plan, an
Employee Stock Ownership Plan (ESOP), health and dental insurance, life and
long-term disability insurance and tuition assistance.


                                       22
<PAGE>   23

Subsidiaries

     The Bank has three wholly-owned subsidiaries:  Readibank Investment
Corporation, Melbank Investment Corporation, and Readibank Properties, Inc.

     Readibank Investment Corporation and Melbank Investment Corporation were
established for the purpose of managing portions of the Bank's investment
portfolio. Assets of Readibank Investment Corporation and Melbank Investment
Corporation totaled $91.9 million and $97.1 million, at December 31, 1998,
respectively.

     Readibank Properties, Inc. incorporated primarily for the purpose of real
estate development, had total assets of $630 thousand at December 31, 1998.

Executive Officers of the Registrant

     The executive officers of the Company and the Bank and the age of each
officer as of March 4, 1999 are as follows:

Name                           Age        Office

Gerard H. Brandi               50         Chairman of the Board of Directors,
                                          President and Chief Executive
                                          Officer of the Company and the Bank

David F. Carroll               51         Vice President of the Bank

Reginald E. Cormier            51         Vice President, Treasurer and Chief
                                          Financial Officer of the Company and
                                          the Bank

Thomas J. Queeney              36         Vice President and Senior Trust
                                          Officer of the Bank

Donald R. Washburn             55         Senior Vice President of the Bank

Donna H. West                  53         Senior Vice President of the Bank
                                          and Assistant Secretary of the
                                          Company


                                       23
<PAGE>   24

     Gerard H. Brandi.  Mr. Brandi has served in various capacities with
MASSBANK since he joined the Bank in 1975 as Vice President of the Lending
Division.  He served as Senior Vice President from 1978 to 1981, Executive
Vice President and Senior Lending Officer from 1981 to 1983, and Executive
Vice President and Treasurer from 1983 to 1986.  Mr. Brandi was named
President of the Company and the Bank in 1986, Chief Executive Officer in 1992
and Chairman in 1993.

     David F. Carroll.  Mr. Carroll has been employed by the Bank since 1983
and has been Vice President of Operations since 1984.  He served as Vice
President of the Lending Division for a year before becoming Vice President of
Operations.

     Reginald E. Cormier.  Mr. Cormier joined the Bank as Treasurer in
September, 1987 and has served in this capacity until his promotion to Vice
President, Treasurer and Chief Financial Officer in January, 1995.

     Thomas J. Queeney. Mr. Queeney joined the Bank in 1986 as a Management
Trainee in Loan Origination. He became an Assistant Manager in 1987 and was
promoted to Assistant Treasurer in 1988. He then served as a Marketing and
Investor Relations Representative until his promotion to Loan Servicing Manager
in 1990. In 1992, he was promoted to Loan Officer and Commercial Lending
Manager. He was promoted to Assistant Vice President, Lending in 1997, where he
served until his promotion to AVP/Trust Administrator in July of 1998. In
January of 1999, he was promoted to Vice President and Senior Trust Officer.

     Donald R. Washburn.  Mr. Washburn joined the Bank in 1973 as a Loan
Officer.  He became an Assistant Vice President in January, 1977 and a Vice
President in the Lending Division in June, 1980.  Mr. Washburn served as Vice
President of the Operations Division from February, 1983 to January, 1984, as
Vice President of the Community Banking Division from January, 1984 to
January, 1986 and as Vice President of the Lending Division from January, 1986
until his promotion to Senior Vice President of the Lending Division in June,
1994.

     Donna H. West.  Mrs. West has been employed by the Bank since 1979 and
has served as Vice President of the Community Banking Division since October,
1987. Starting at the Bank as an Assistant Branch Manager in 1979, Mrs. West
became a Branch Manager in 1981, an Assistant Treasurer and Branch Manager in
1982, an Assistant Treasurer and Regional Branch Administrator in 1984 and an
Assistant Vice President and Regional Branch Administrator in 1986.  She
served in this capacity until her October, 1987 promotion to Vice President of
the Community Banking Division.  In June, 1994, Mrs. West was promoted to
Senior Vice President of the Community Banking Division.


                                       24
<PAGE>   25

Item 2. Properties

     The main office of MASSBANK Corp. and MASSBANK is located at 123 Haven
Street, Reading, Massachusetts. Additionally, the Bank has fourteen branches and
three operations facilities. The Bank owns its main office, two operations
facilities and seven of its branches. All of the remaining branches and other
facilities are leased under various leases. At December 31, 1998, management
believes that the Bank's existing facilities are adequate for the conduct of its
business.

     The following table sets forth certain information relating to the Bank's
existing facilities.

                                                    Owned   Lease       Renewal
                                                    or      Expiration  Option
Location                                            Leased  Date        Through

MAIN OFFICE:  123 Haven Street, Reading, MA          Owned   ----        ----
BRANCH        296 Chelmsford Street, Chelmsford, MA  Leased  1998        ----
 OFFICES:     17 North Road, Chelmsford, MA          Leased  1999        (1)
              45 Broadway Road, Dracut, MA           Leased  2002        ----
              738 Broadway, Everett, MA              Owned   ----        ----
              50 Central Street, Lowell, MA          Owned   ----        ----
              755 Lakeview Avenue, Lowell, MA        Owned   ----        ----
              4110 Mystic Valley Pkwy, Medford, MA   Leased  2001        ----
              476 Main Street, Melrose, MA           Owned   ----        ----
              27 Melrose Street, Towers Plaza,
                 Melrose, MA                         Leased  2004        2014
              240 Main Street, Stoneham, MA          Leased  2003        ----
              1800 Main Street, Tewksbury, MA        Owned   ----        ----
              203 Littleton Road, Westford, MA       Owned   ----        ----
              370 Main Street, Wilmington, MA        Owned   ----        ----
              219 Lowell Street, Lucci's Plaza,
                 Wilmington, MA                      Leased  2006        ----
OPERATIONS
 FACILITIES:  159 Haven Street, Reading, MA          Owned   ----        ----
              169 Haven Street, Reading, MA          Owned   ----        ----
              11 North Road, Chelmsford, MA          Leased  1999        (1)

(1) Bank has option to purchase in year 2000.


Item 3. Legal Proceedings

     From time to time, MASSBANK Corp. and/or the Bank are involved as a
plaintiff or defendant in various legal actions incident to their business. As
of December 31, 1998, none of these actions individually or in the aggregate is
believed by management to be material to the financial condition of MASSBANK
Corp. or the Bank.

Item 4. Submission of Matters to a Vote of Security Holders

     None.


                                       25
<PAGE>   26

                                    PART II

Item 5. Market for Registrant's Common Equity and Related Stockholder Matters

     The information contained under the caption "MASSBANK Corp. and
Subsidiaries Stockholder Data" in the Registrant's 1998 Annual Report to
Stockholders is incorporated herein by reference.

Item 6. Selected Financial Data

     The information contained under the caption "MASSBANK Corp. and
Subsidiaries - Selected Consolidated Financial Data" in the Registrant's 1998
Annual Report to Stockholders is incorporated herein by reference.

     This selected consolidated financial data should be read in conjunction
with the consolidated statements and related notes thereto appearing in the
Registrant's 1998 Annual Report to Stockholders which are incorporated herein by
reference.

Item 7. Management's Discussion and Analysis of Financial Condition and Results
        of Operations

     The information contained under the caption "Management's Discussion and
Analysis of Financial Condition and Results of Operations" in the Registrant's
1998 Annual Report to Stockholders is incorporated herein by reference.

Item 8. Financial Statements and Supplementary Data

     The Registrant's consolidated financial statements and notes thereto,
together with the report of KPMG Peat Marwick LLP, contained in the Registrant's
1998 Annual Report to Stockholders are incorporated herein by reference. The
unaudited quarterly financial data set forth on page 48 of such Annual Report is
incorporated herein by reference.

Item 9. Changes in and Disagreements with Independent Accountants on
        Accounting and Financial Disclosure

         None



                                    PART III

Item 10. Directors and Executive Officers of the Registrant

         The information appearing under the caption "Election of Directors" and
"Compliance with Section 16(A) of the Exchange Act" in the Registrant's
definitive proxy statement relating to its 1999 Annual Meeting of Stockholders
is incorporated herein by reference. Information required by this item
concerning the Executive Officers of the Registrant is contained in Part I of
this Form 10-K.

Item 11. Executive Compensation

         The information appearing under the caption "Executive Compensation" in
the Registrant's definitive proxy statement relating to its 1999 Annual Meeting
of Stockholders is incorporated herein by reference.


                                       26
<PAGE>   27

Item 12. Security Ownership of Certain Beneficial Owners and Management

         The information appearing under the captions "Election of Directors"
and "Principal Stockholders" in the Registrant's definitive proxy statement
relating to its 1999 Annual Meeting of Stockholders is incorporated herein by
reference.

Item 13. Certain Relationships and Related Transactions

         The information contained in Note 5 of the Consolidated Financial
Statements under the caption "Loans" in the Registrant's 1998 Annual Report to
Stockholders is incorporated herein by reference.


                                    PART IV

Item 14. Exhibits, Financial Statement Schedules and Reports on Form 8-K

         The following financial statements and financial statement schedules
are contained herein or are incorporated herein by reference:

(a)1. Financial Statements
                                                              Reference to 1998
                                                                Annual Report
                                                               to Stockholders
                                                                   (Pages)


Independent Auditors' Report                                         21
Consolidated balance sheets at December 31,
  1998 and 1997                                                      22
Consolidated statements of income for the three
  years ended December 31, 1998                                      23
Consolidated statements of cash flows for the three
  years ended December 31, 1998                                   24-25
Consolidated statements of changes in stockholders'
  equity for the three years ended December 31,
  1998                                                               26
Notes to consolidated financial statements                        27-48


   2. Financial Statement Schedules

         All schedules are omitted as the required information is either not
applicable or is included in the consolidated financial statements or related
notes.


                                       27
<PAGE>   28

   3. Exhibits

  Exhibit No.         Description of Exhibit

     3.1              Restated Certificate of Incorporation of the
                      Registrant - incorporated by reference to Exhibit
                      3.1 of the Registrant's Form S-4 Registration
                      Statement (Reg. No. 33-7916).

     3.2              By-Laws of the Registrant - incorporated by reference
                      to Exhibit 3 of the Registrant's Form 10-Q for the
                      quarter ended September 30, 1991.

     4.1              Shareholder Rights Agreement dated as of
                      January 16, 1990, between the Company and The First
                      National Bank of Boston, as Rights Agent - incorporated
                      herein by reference to the Exhibit to the Company's
                      Current Report on Form 8-K dated as of January 16, 1990.

    10.1              MASSBANK Corp. 1986 Stock Option Plan, as amended -
                      incorporated by reference to Exhibit 28.1 to the
                      Registrant's Form S-8 Registration Statement
                      (Reg. No. 33-11949).

    10.1.2            Amendment to MASSBANK Corp. 1986 Stock Option Plan dated
                      April 19, 1991 - incorporated by reference to Exhibit
                      10.1.2 to the Registrant's annual report on Form 10-K for
                      the year ended December 31, 1992.

    10.1.3            MASSBANK Corp. 1994 Stock Incentive Plan - incorporated
                      by reference to Exhibit 10.1 to the Registrant's Form S-8
                      Registration Statement (Reg. No. 33-82110).

    10.1.4            Amendment to MASSBANK Corp. 1994 Stock Incentive Plan
                      dated April 21, 1998 - incorporated by reference to
                      Exhibit 10.1.4 to the Registrant's annual report on Form
                      10-K for the year ended December 31, 1997.

    10.2              MASSBANK for Savings Employees' Stock Ownership Plan
                      and Trust Agreement - incorporated by reference to
                      Exhibit 10.2 of the Registrant's Form S-4 Registration
                      Statement (Reg. No. 33-7916).

    10.2.1            Amendments to the MASSBANK for Savings Employee's Stock
                      Ownership Plan and Trust Agreement - incorporated by
                      reference to Exhibit 10.2.1 to the Registrant's annual
                      report on Form 10-K for the year ended December 31, 1993.

    10.2.2            Amendments to the MASSBANK for Savings Employee's Stock
                      Ownership Plan and Trust Agreement - incorporated by
                      reference to Exhibit 10.2.2 to the Registrant's annual
                      report on Form 10-K for the year ended December 31, 1997.

    10.3              Form of Employment Agreement, as amended, with Gerard H.
                      Brandi - incorporated by reference to Exhibit 10.3 of
                      the Registrant's annual report on Form 10-K for the year
                      ended December 31, 1986 and Exhibit 10.3.1 of the
                      Registrant's annual report on Form 10-K for the year
                      ended December 31, 1989.


                                       28
<PAGE>   29

  Exhibit No.         Description of Exhibit



    10.3.2            Amendment to the Employment Agreement with Gerard H.
                      Brandi - incorporated by reference to Exhibit 10.3.2 of
                      the Registrant's annual report on Form 10-K for the year
                      ended December 31, 1990.

    10.3.3            Second amendment dated as of February 1, 1993 to the
                      Employment Agreement with Gerard H. Brandi - incorporated
                      by reference to Exhibit 10.3.3. to the Registrant's annual
                      report on Form 10-K for the year ended
                      December 31, 1992.

    10.3.7            Form of Employment Agreement with David F. Carroll dated
                      as of February 1, 1993 - incorporated by reference to
                      Exhibit 10.3.7 to the Registrant's annual report on Form
                      10-K for the year ended December 31, 1992.

    10.3.8            Form of Employment Agreement with Reginald E. Cormier
                      dated as of February 1, 1993 - incorporated by reference
                      to Exhibit 10.3.8 to the Registrant's annual report on
                      Form 10-K for the year ended December 31, 1992.

    10.3.9            Form of Employment Agreement with Donald R. Washburn dated
                      as of February 1, 1993 - incorporated by reference to
                      Exhibit 10.3.9 to the Registrant's annual report on Form
                      10-K for the year ended December 31, 1992.

    10.3.10           Form of Employment Agreement with Donna H. West dated as
                      of February 1, 1993 - incorporated by reference to Exhibit
                      10.3.10 to the Registrant's annual report on Form 10-K for
                      the year ended December 31, 1992.

    10.3.11           Executive Severance Agreement with Gerard H. Brandi dated
                      as of January 18, 1994 - incorporated by reference to
                      exhibit 10.3.11 to the Registrant's annual report on Form
                      10-K for the year ended December 31, 1993.

    10.3.12           Executive Severance Agreement with David F. Carroll dated
                      as of December 23, 1993 - incorporated by reference to
                      exhibit 10.3.12 to the Registrant's annual report on Form
                      10-K for the year ended December 31, 1993.

    10.3.13           Executive Severance Agreement with Reginald E. Cormier
                      dated as of December 23, 1993 - incorporated by reference
                      to exhibit 10.3.13 to the Registrant's annual report on
                      Form 10-K for the year ended December 31, 1993.


                                       29
<PAGE>   30

  Exhibit No.         Description of Exhibit


    10.3.14           Executive Severance Agreement with Donald R. Washburn
                      dated as of December 23, 1993 - incorporated by reference
                      to exhibit 10.3.14 to the Registrant's annual report on
                      Form 10-K for the year ended December 31, 1993.

    10.3.15           Executive Severance Agreement with Donna H. West dated as
                      of December 23, 1993 - incorporated by reference to
                      exhibit 10.3.15 to the Registrant's annual report on Form
                      10-K for the year ended December 31, 1993.

    10.4              Form of Executive Supplemental Retirement Agreement, as
                      amended, with Gerard H. Brandi - incorporated by
                      reference to Exhibit 10.4 of Registrant's annual report
                      on Form 10-K for the year ended December 31, 1986.

    10.4.1            Amendments to the Executive Supplemental Retirement
                      Agreement with Gerard H. Brandi are incorporated by
                      reference to Exhibit 10.4.1 of the Registrant's annual
                      report on Form 10-K for the year ended December 31, 1996.

    12                Statement re: Computation of Ratios - Not applicable as
                      MASSBANK Corp. does not have any debt securities
                      registered under Section 12 of the Securities Exchange
                      Act of 1934.

    13                1998 Annual Report to Stockholders - except for those
                      portions of the 1998 Annual Report to Stockholders which
                      are expressly incorporated by reference in this report,
                      such 1998 Annual Report to Stockholders is furnished for
                      the information of the SEC and is not to be deemed
                      "filed" with the SEC.

    22                Subsidiaries of the Registrant - A list of subsidiaries
                      of the Registrant is attached hereto as Exhibit 22 to
                      this Annual Report.

    23                Consent of Independent Auditors.

    (b)               Reports on Form 8-K
                      No reports on Form 8-K have been filed during the last
                      quarter of the period covered by this Form 10-K.

    (c)               Exhibits to this Form 10-K are attached or incorporated by
                      reference as stated in the Index to Exhibits.

    (d)               Not applicable.


                                       30
<PAGE>   31

                                   Signatures

     Pursuant to the requirements of Section 13 or 15(d) of the Securities Act
of 1934, the Registrant has duly caused this report to be signed on its behalf
by the undersigned, thereunto duly authorized.

                               MASSBANK CORP.


                               /s/ Gerard H. Brandi
                               --------------------
                               Gerard H. Brandi
                               Chairman, President and Chief Executive Officer


     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 and on the dates indicated.




/s/ Gerard H. Brandi           Chairman, President,
------------------------------ Chief Executive Officer and                    
Gerard H. Brandi               Director                         March 26, 1999
                               



/s/ Reginald E. Cormier        Vice President, Treasurer
------------------------------ and Chief Financial Officer                     
Reginald E. Cormier            (Principal Financial and                        
                               Accounting Officer)              March 26, 1999 
                              



/s/ Samuel Altschuler          Director                         March 26, 1999
------------------------------
Samuel Altschuler



/s/ Mathias B. Bedell          Director                         March 26, 1999
------------------------------
Mathias B. Bedell



                               Director
------------------------------
Allan S. Bufferd



                               Director
------------------------------
Peter W. Carr



/s/ Alexander S. Costello      Director                         March 26, 1999
------------------------------
Alexander S. Costello


                                       31
<PAGE>   32

/s/ Robert S. Cummings         Director                         March 26, 1999
------------------------------
Robert S. Cummings



/s/ Louise A. Hickey           Director                         March 26, 1999
------------------------------
Louise A. Hickey



                               Director
------------------------------
Leonard Lapidus



/s/ Stephen E. Marshall        Director                         March 26, 1999
------------------------------
Stephen E. Marshall



/s/ Arthur W. McPherson        Director                         March 26, 1999
------------------------------
Arthur W. McPherson



/s/ Nancy L. Pettinelli        Director                         March 26, 1999
------------------------------
Nancy L. Pettinelli



/s/ Herbert G. Schurian        Director                         March 26, 1999
------------------------------
Herbert G. Schurian



/s/ Donald B. Stackhouse       Director                         March 26, 1999
------------------------------
Donald B. Stackhouse


                                       32