<PAGE>   1
                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    FORM 10-Q

 (Mark One)        [X]     QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF
                           THE SECURITIES EXCHANGE ACT OF 1934

                                       OR

                   [ ]     TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF
                           THE SECURITIES EXCHANGE ACT OF 1934

                  For the quarterly period ended JUNE 30, 2000



                        Commission file number 0 - 12784


                              WESTBANK CORPORATION
             (Exact name of registrant as specified in its charter)


<TABLE>
<S>                                                                   <C>
                         MASSACHUSETTS                                        04-2830731
(State or other jurisdiction of incorporation or organization)        (I.R.S. Employer I.D. No.)


         225 PARK AVENUE, WEST SPRINGFIELD, MASSACHUSETTS                     01090-0149
             (Address of principal executive offices)                         (Zip Code)
</TABLE>


                                 (413) 747-1400
              (Registrant's telephone number, including area code)


         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
                                     ---    ---


         Common stock, par value $2.00 per share: 4,208,907 shares outstanding
         as of July 31, 2000
<PAGE>   2
                      WESTBANK CORPORATION AND SUBSIDIARIES

                                      INDEX



                         PART I - FINANCIAL INFORMATION



<TABLE>
<CAPTION>
                                                                            Page
<S>                                                                         <C>
Financial Statements
      Condensed Consolidated Balance Sheets                                    3
      Condensed Consolidated Statements of Income                              4
      Condensed Consolidated Statements of Comprehensive Income                5
      Condensed Consolidated Statements of Stockholders' Equity                6
      Condensed Consolidated Statements of Cash Flows                          7
      Notes to Condensed Consolidated Financial Statements                     8-9
      Management's Discussion and Analysis of
           Financial Condition and Results of Operations                      10-17



                           PART II - OTHER INFORMATION


ITEM 1.       Legal Proceedings                                               18
ITEM 2.       Changes in Rights of Securities Holders                         18
ITEM 3.       Defaults by Company on its Senior Securities                    18
ITEM 4.       Results of Votes on Matters Submitted
                    to a Vote of Security Holders                             18
ITEM 5.       Other Events                                                    18
ITEM 6.       Exhibits and Reports on Form 8-K                                19
Signatures                                                                    20
</TABLE>


                                       2
<PAGE>   3
WESTBANK CORPORATION AND SUBSIDIARIES
CONDENSED CONSOLIDATED BALANCE SHEETS



<TABLE>
<CAPTION>
                                                                (Unaudited)
(Dollar amounts in thousands)                                  June 30, 2000    December 31, 1999
-----------------------------                                  -------------    -----------------
<S>                                                            <C>              <C>
ASSETS
      Cash and due from banks:
      Non-interest bearing                                       $  16,118         $  17,006
      Interest bearing                                                 572             1,147
Federal funds sold                                                   1,426            13,389
                                                                 ---------         ---------
Total cash and cash equivalents                                     18,116            31,542
                                                                 ---------         ---------
Investment securities available for sale                            87,751            69,516
Investment securities held to maturity
      (fair value of $11,250 in 2000 and $11,472 in 1999)           11,596            11,804
                                                                 ---------         ---------
Total securities                                                    99,347            81,320
                                                                 ---------         ---------
Loans                                                              447,527           440,319
Mortgage loans held-for-sale                                         2,042             2,156
Allowance for loan losses                                           (3,896)           (3,908)
                                                                 ---------         ---------
      Net loans                                                    445,673           438,567
Bank premises and equipment                                          7,484             7,809
Other real estate owned                                                672               442
Accrued interest receivable                                          3,848             3,243
Intangible assets                                                    9,685             9,971
Other assets                                                         4,729             3,256
                                                                 ---------         ---------
TOTAL ASSETS                                                     $ 589,554         $ 576,150
                                                                 =========         =========
LIABILITIES AND STOCKHOLDERS' EQUITY
Deposits:
      Non-interest bearing                                       $  58,168         $  59,643
      Interest bearing                                             428,924           419,253
                                                                 ---------         ---------
      Total Deposits                                               487,092           478,896
Borrowed funds                                                      50,742            46,546
Accrued interest payable                                               569               732
Other liabilities                                                    2,396             1,433
                                                                 ---------         ---------
      Total Liabilities                                            540,799           527,607
                                                                 ---------         ---------
Mandatory redeemable preferred stock                                17,000            17,000
                                                                 ---------         ---------
Stockholders' Equity:
      Common stock     -  $2.00 par value
           Authorized  -  9,000,000 shares
           Issued      -  4,192,882 shares in 2000 and
                          4,283,719 shares in 1999                   8,567             8,567
      Additional paid in capital                                    11,638            11,633
      Retained earnings                                             14,445            13,317
      Treasury stock                                                  (799)
      Accumulated other comprehensive income (loss)                 (2,096)           (1,974)
                                                                 ---------         ---------
           Total Stockholders' Equity                               31,755            31,543
                                                                 ---------         ---------
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY                       $ 589,554         $ 576,150
                                                                 =========         =========
</TABLE>

     See accompanying notes to condensed consolidated financial statements.

                                        3
<PAGE>   4
WESTBANK CORPORATION AND SUBSIDIARIES
CONDENSED CONSOLIDATED STATEMENTS OF INCOME



<TABLE>
<CAPTION>
(Unaudited)
(Dollar amounts in thousands)
                                                                     QUARTER ENDED                    SIX MONTHS ENDED
                                                                6-30-00       06-30-99            06-30-00        06-30-99
                                                                -------       --------            --------        --------
<S>                                                           <C>           <C>                  <C>             <C>
Income:
      Interest and fees on loans                                 $8,815        $6,504              $17,507         $12,533
      Interest on federal funds sold                                 28            35                   96              73
      Interest on securities                                      1,723         1,114                3,246           2,390
                                                                 ------        ------              -------         -------
                                                                 10,566         7,653               20,849          14,996
Interest expense                                                  5,665         3,481               10,960           6,806
                                                                 ------        ------              -------         -------
Net interest income                                               4,901         4,172                9,889           8,190
Provision for loan losses                                            75             2                  140              77
                                                                 ------        ------              -------         -------
Net interest income after provision                               4,826         4,170                9,749           8,113
                                                                 ------        ------              -------         -------
Investment security gains                                                                                               92
Other non-interest income                                           606           492                1,184           1,018
                                                                 ------        ------              -------         -------
Total non-interest income                                           606           492                1,184           1,110
                                                                 ------        ------              -------         -------
Operating expense:
      Salaries and benefits                                       1,920         1,470                3,962           2,967
      Other operating expenses                                    1,509         1,163                3,189           2,273
      Occupancy - net                                               332           306                  686             614
                                                                 ------        ------              -------         -------
Total operating expenses                                          3,761         2,939                7,837           5,854
                                                                 ------        ------              -------         -------
Income before income taxes                                        1,671         1,723                3,096           3,369
Income taxes                                                        592           652                1,116           1,277
                                                                 ------        ------              -------         -------
Net Income                                                       $1,079        $1,071              $ 1,980        $  2,092
                                                                 ======        ======              =======        ========

Earnings per share
           -  Basic                                               $0.26         $0.25                $0.47           $0.50
           -  Diluted                                             $0.25         $0.25                $0.46           $0.48
Weighted average shares outstanding
           -  Basic                                           4,204,822     4,225,943            4,238,753       4,218,407
           -  Dilutive option shares                             50,042        94,132               54,018         118,172
           -  Diluted                                         4,254,864     4,320,075            4,292,771       4,336,579
</TABLE>



     See accompanying notes to condensed consolidated financial statements.

                                        4
<PAGE>   5
WESTBANK CORPORATION AND SUBSIDIARIES
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME



<TABLE>
<CAPTION>
(Unaudited)
(Dollar amounts in thousands)
                                                           QUARTER ENDED                 SIX MONTHS ENDED
                                                      06-30-00       06-30-99        06-30-00        06-30-99
                                                      --------       --------        --------        --------
<S>                                                   <C>            <C>             <C>             <C>
Net Income                                             $ 1,079        $ 1,071         $ 1,980         $ 2,092
                                                       -------        -------         -------         -------
Other comprehensive income:
      Unrealized gain/(loss) on securities
      available for sale, net of income
      taxes (benefits) of $9 and $(481) for the
      quarter and $(75) and $(733) for
      the six-month periods ended June 30, 2000
      and 1999, respectively                                16           (785)           (122)         (1,196)

      Reclassification adjustment for
      gains included in net income,
      net of income taxes of $35 for
      the six-month period ended
      June 30, 1999                                                                                        57
                                                       -------        -------         -------         -------
Other comprehensive income (loss)                           16           (785)           (122)         (1,139)
                                                       -------        -------         -------         -------
Comprehensive Income                                   $ 1,095        $   286         $ 1,858         $   953
                                                       =======        =======         =======         =======
</TABLE>

     See accompanying notes to condensed consolidated financial statements.

                                        5
<PAGE>   6
WESTBANK CORPORATION AND SUBSIDIARIES
CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY
YEAR ENDED DECEMBER 31, 1999 AND SIX MONTHS ENDED JUNE 30, 2000


(2000 unaudited)
(Dollar amounts in thousands)


<TABLE>
<CAPTION>
                                                                                                         ACCUMULATED
                                                                                                           OTHER
                                              COMMON STOCK        ADDITIONAL                            COMPREHENSIVE
                                           NUMBER         PAR      PAID IN       RETAINED    TREASURY      INCOME/
                                          OF SHARES      VALUE     CAPITAL       EARNINGS     STOCK        (LOSS)         TOTAL
<S>                                       <C>           <C>       <C>            <C>         <C>        <C>              <C>
BALANCE - DECEMBER 31, 1998               4,198,838     $8,397     $11,076        $10,803                    $    214    $30,490

Net income                                                                          4,167                                  4,167
Cash dividend declared
  ($.40 per share)                                                                 (1,653)                                (1,653)

Shares issued:
  Stock Option Plan                          30,255         61            78                                                 139
  Dividend Reinvestment
      and Stock Purchase Plan                54,626        109           479                                                 588
  Changes in unrealized loss on
      securities available for sale                                                                            (2,188)    (2,188)
                                          ---------     ------       -------      -------      ------         -------    -------
BALANCE - DECEMBER 31, 1999               4,283,719      8,567        11,633       13,317                      (1,974)    31,543

Net income                                                                          1,980                                  1,980
Cash dividend declared
  ($.20 per share)                                                                   (852)                                  (852)

Treasury Shares:
  Redeemed                                 (123,200)                                          $(1,097)                    (1,097)
  Reissued                                   32,363                        5                      298                        303
  Changes in unrealized loss on
      securities available for sale                                                                              (122)      (122)
                                          ---------     ------       -------      -------      ------         -------    -------
BALANCE - JUNE 30, 2000                   4,192,882     $8,567       $11,638      $14,445      $ (799)        $(2,096)   $31,755
                                          =========     ======       =======      =======      ======         =======    =======
</TABLE>



     See accompanying notes to condensed consolidated financial statements.

                                        6
<PAGE>   7
WESTBANK CORPORATION
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOW
SIX MONTHS ENDED JUNE 30, 2000 AND 1999

(Unaudited)
(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                                                               2000             1999
<S>                                                                          <C>              <C>
Operating activities:
      Net income                                                             $  1,980         $  2,092
           Adjustments to reconcile net income to
           net cash provided by operating activities:
                Provision for loan losses                                         140               77
                Depreciation and amortization                                     525              471
                Intangible amortization                                           286
                Realized gain on sale of securities                                                (92)
                Realized gain on sale of other real estate owned                                    19
                Increase in accrued interest receivable                          (605)            (144)
                Increase in other assets                                       (1,473)            (618)
                Increase/(Decrease) in interest payable on deposits              (163)              41
                Increase/(Decrease) in other liabilities                        1,186             (784)
                                                                             --------         --------
                Net cash provided by operating activities                       1,876            1,062
                                                                             --------         --------
Investing activities:
      Investments and mortgage-backed securities:
           Held to maturity:
                Purchases                                                                       (1,050)
                Proceeds from maturities and principal payments                   208           19,106
           Available for sale:
                Purchases                                                     (19,366)         (20,686)
                Proceeds from sales                                                              4,679
                Proceeds from maturities                                          878           10,307
      Purchases of premises and equipment                                        (200)            (530)
      Net (increase)/decrease in loans                                         (7,423)         (44,417)
      Proceeds from sale of other real estate owned                                78              381
                                                                             --------         --------
           Net cash used in investing activities                              (25,825)         (32,210)
                                                                             --------         --------
Financing activities:
      Net increase in borrowed funds                                            3,973            4,250
      Net increase in deposits                                                  8,196           27,817
      Proceeds from exercise of stock options and stock purchase plan                              324
      Treasury stock (purchased)/issued, net                                     (794)
      Dividends paid                                                             (852)            (801)
                                                                             --------         --------
           Net cash provided by financing activities                           10,523           31,590
                                                                             --------         --------
Increase/(Decrease) in cash and cash equivalents                              (13,426)             442
Cash and cash equivalents at beginning of period                               31,542           14,240
                                                                             --------         --------
Cash and cash equivalents at end of period                                   $ 18,116         $ 14,682
                                                                             ========         ========
Cash paid during the period:
      Interest on deposits and other borrowings                              $ 11,123         $  6,765
      Income taxes                                                              1,147            1,191
Supplemental disclosure of cash flow information:
      Transfers of loans to other real estate owned                               308
</TABLE>


     See accompanying notes to condensed consolidated financial statements.

                                        7
<PAGE>   8
WESTBANK CORPORATION AND SUBSIDIARIES
NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
QUARTER AND SIX MONTHS ENDED JUNE 30, 2000 AND JUNE 30, 1999


(Unaudited)


NOTE A  -  GENERAL INFORMATION

Westbank Corporation (hereinafter sometimes referred to as "Westbank" or the
"Corporation") is a registered Financial Holding Company organized to facilitate
the expansion and diversification of the business of Park West Bank and Trust
Company and Cargill Bank (hereinafter sometimes referred to as "Park West" or
"Cargill" and collectively as the "Banks") into additional financial services
related to banking. Substantially all operating income and net income of the
Corporation are presently accounted for by Park West and Cargill.


NOTE B  -  CURRENT OPERATING ENVIRONMENT

Park West operates thirteen banking offices located in Hampden County,
Massachusetts, and also operates a Trust Department providing services normally
associated with holding property in a fiduciary or agency capacity. A full range
of retail banking services is furnished to individuals, businesses and
non-profit organizations. Cargill Bank operates five offices in Windham County,
Connecticut. A full range of retail banking services is furnished to
individuals, businesses and non-profit organizations. The primary source of
revenue for Park West and Cargill is derived from providing loans to customers
who are predominantly located in Park West's and Cargill's service areas.

The Federal Deposit Insurance Corporation Improvement Act of 1991 ("FDICIA")
imposes significant regulatory restrictions and requirements on banking
institutions insured by the FDIC and their holding companies. FDICIA established
capital categories into which financial institutions are placed based on capital
level. Each capital category establishes different degrees of regulatory
restrictions that can apply to a financial institution. As of June 30, 2000,
Park West and Cargill's capital was at a level that placed the Banks in the
"well capitalized" category as defined by FDICIA.

FDICIA imposes a variety of other restrictions and requirements on insured
banks. These include significant regulatory reporting requirements such as
insuring that a system of risk-based deposit insurance premiums and civil money
penalties for inaccurate deposit assessment reports exists. In addition, FDICIA
imposes a system of regulatory standards for bank and bank holding company
operations, detailed truth in savings disclosure requirements, and restrictions
on activities authorized by state law but not authorized for national banks.


NOTE C  -  BASIS OF PRESENTATION

The accompanying unaudited condensed consolidated financial statements for the
quarter and six months ended June 30, 2000 and 1999 have been prepared in
accordance with generally accepted accounting principles for interim information
and with instructions for Form 10-Q. Accordingly, they do not include all of the
information and notes required by generally accepted accounting principles for
complete financial statements. In the opinion of management, all adjustments
(consisting or normal recurring accruals) considered necessary for a fair
presentation have been included. Operating results for the quarter and six-month
period ended June 30, 2000 are not necessarily indicative of the results that
may be expected for the year ending December 31, 2000.

For further information, please refer to the Consolidated Financial Statements
and footnotes thereto included in the Westbank Corporation's Annual Report on
Form 10-K for the year ended December 31, 1999.

                                        8
<PAGE>   9
NOTE D  -  ACQUISITION OF BRANCHES

On October 29, 1999, the Corporation completed its acquisition of the
Connecticut division of New London Trust, F.S.B. The two New London Trust
offices became part of Cargill Bank, increasing its number of offices to five.
The Corporation has accounted for this acquisition on the purchase method,
including the results of their operations since October 29, 1999. The intangible
assets are being amortized over fifteen (15) years.

The pro forma results of operations for the quarter and six months ended June
30, 1999, as if this acquisition had occurred at the beginning of 1999, were as
follows:

<TABLE>
<CAPTION>
                                                 Quarter              Six Months
                                                 -------              ----------
<S>                                              <C>                  <C>
           Net interest income                   $5,032                 $9,910
           Net income                            $1,072                 $2,094
           Basic earnings per share               $0.25                  $0.50
           Diluted earnings per share             $0.25                  $0.48
</TABLE>

NOTE E  -  COMMITMENTS AND CONTINGENT LIABILITIES

In the normal course of business, there are outstanding commitments and
contingent liabilities, such as standby letters of credit and commitments to
extend credit. As of June 30, 2000, standby letters of credit amounted to
$764,000 and loan commitments were $28,497,000 and unused balances available on
home equity lines of credit were $11,966,000.

Trust Assets - Property with a book value of $115,858,000 at June 30, 2000 held
for customers in a fiduciary or agency capacity is not included in the
accompanying balance sheet since such items are not assets of the Bank.


NOTE F  -  STOCKHOLDERS' EQUITY

The FDIC imposes leverage capital ratio requirements for state non-member banks.
In addition, the FDIC has established risk-based capital requirements for
insured institutions for Tier 1 risk-based capital of 4.00% and total risk-based
capital of 8.0%.

The capital ratios of Park West and Cargill as of June 30, 2000 were as follows:


<TABLE>
<CAPTION>
                                            Park West Bank
                                         and Trust Company          Cargill Bank
                                         -----------------          ------------
<S>                                      <C>                        <C>
      Leverage Capital Ratio                     7.34%                     5.92%
      Tier 1 Risk-Based Capital                 10.77%                    10.95%
      Total Risk-Based Capital                  11.64%                    12.20%
</TABLE>


As of June 30, 2000, both Park West and Cargill met the criteria which
classified them as well capitalized financial institutions.

                                        9
<PAGE>   10
MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS



Changes in Financial Condition

Total consolidated assets amounted to $589,554,000 on June 30, 2000, compared to
$576,150,000 on December 31, 1999. As of June 30, 2000 and June 30, 1999,
earning assets amounted to, respectively, $550,914,000 or 93% of total assets
and $538,331,000 or 93% of total assets. Earning assets increased during the
first six months of 2000 as a result of an increase in loans and investments.
Deposits originated throughout the Corporation's branch system and short-term
borrowings with the Federal Home Loan Banks funded the growth in assets.


Changes in Results of Operations

For the quarter ended June 30, 2000, net income totaled $1,079,000, compared to
$1,071,000 for the quarter ended June 30, 1999. For the six months ended June
30, 2000, net income was $1,980,000, compared to $2,092,000 for the same period
during 1999. Included in the results for the six months ended June 30, 2000 were
approximately $230,000 in expenses related to the integration of the branch
acquisition in northeast Connecticut.

An overall increase in interest income and interest expense reflects an increase
in volume and interest rates on earning assets and an increase in volume and
increase in rates on interest-bearing liabilities. Further analysis is provided
in sections on net interest revenue and supporting schedules.


Allowance for Loan Losses and Non-Performing Assets

The Corporation's provision for loan losses in the current quarter was $75,000,
compared to $2,000 for the same period in 1999. Loans written off against the
allowance for loan losses after recoveries amounted to $152,000 for the six
months ended June 30, 2000.

After giving effect to the actions described above, the allowance for loan
losses at June 30, 2000, totaled $3,896,000 or .87% of total loans, as compared
to $3,908,000 or .87% at December 31, 1999.

Non-performing past due loans at June 30, 2000, aggregated $1,469,000 or .33% of
total loans, compared to $2,439,000 or .55% at December 31, 1999. The percentage
of non-performing and past due loans compared to total assets on those same
dates, respectively, amounted to .25% and .42%. The change in non-performing
loans was primarily the result of the sale of a pool of classified loans during
the first quarter of the year.

Other real estate owned at June 30, 2000, totaled $672,000 and stands at .11% of
total assets at the end of the current quarter.

Management has made every effort to recognize all circumstances known at this
time that could affect the collectibility of loans and has reflected these in
the provision for loan losses, the write-down of other real estate owned and
impaired loans to fair value and other loans (watch list) monitored by
management, the charge-off of loans and the balance in the allowance for loan
losses. Management deems that the provision for the quarter and the balance in
the allowance for loan losses are adequate, based on results provided by the
loan grading system and circumstances known at this time.

                                       10
<PAGE>   11
WESTBANK CORPORATION AND SUBSIDIARIES
MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS
(CONTINUED)


NET INTEREST INCOME

The Corporation's earning assets include a diverse portfolio of earning
instruments, ranging from the Corporation's core business of loan extensions to
interest-bearing securities issued by federal, state and municipal authorities.
These earning assets are financed through a combination of interest-bearing and
interest-free sources.

Net interest income, the most significant component of earnings, is the amount
by which the interest generated by assets exceeds the interest expense on
liabilities.

The Corporation analyzes its performance by utilizing the concepts of interest
rate spread and net yield on earning assets. The interest rate spread represents
the difference between the yield on earning assets and interest paid on
interest-bearing liabilities. The net yield on earning assets is the difference
between the rate of interest on earning assets and the effective rate paid on
all funds - interest-bearing liabilities as well as interest-free sources
(primarily demand deposits and shareholders' equity).

The balances and rates derived for the analysis of net interest income presented
on the following pages reflect the consolidated assets and liabilities of the
Corporation's principal earning subsidiaries, Park West Bank and Trust Company
and Cargill Bank.

 (Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                        QUARTER ENDED               SIX MONTHS ENDED
                                   06-30-00       06-30-99       06-30-00       06-30-99
                                   --------       --------       --------       --------
<S>                                <C>            <C>            <C>            <C>
Interest and dividend income        $10,566        $ 7,653        $20,849        $14,996
Interest expense                      5,665          3,481         10,960          6,806
                                    -------        -------        -------        -------
Net interest income                 $ 4,901        $ 4,172        $ 9,889        $ 8,190
                                    =======        =======        =======        =======
</TABLE>


INTEREST RATE SPREAD AND NET YIELD ON EARNING ASSETS

<TABLE>
<CAPTION>
(Dollar amounts in thousands)
                                         QUARTER ENDED JUNE 30,                       SIX MONTHS ENDED JUNE 30,
                                      2000                   1999                    2000                   1999
                                      ----                   ----                    ----                   ----
                                    Average                 Average                 Average                Average
                                    Balance    Rate         Balance     Rate        Balance     Rate       Balance     Rate
                                    -------    ----         -------     ----        -------     ----       -------     ----
<S>                                <C>         <C>         <C>          <C>        <C>          <C>       <C>          <C>
Earning Assets                     $542,974    7.81%       $403,316     7.59%      $537,227     7.79%     $394,995     7.59%
                                   --------    ----        --------     ----       --------     ----      --------     ----
Interest-bearing
      liabilities                   485,124    4.67         338,717     4.11        479,918     4.57       331,640     4.10
                                   --------    ----        --------     ----       --------     ----      --------     ----
Interest rate spread                           3.14                     3.48                    3.22                   3.49
                                   --------    ----        --------     ----       --------     ----      --------     ----
Interest-free resources
      used to fund
      earning assets                 57,850                  64,599                  57,309                 63,355
                                   --------    ----        --------     ----       --------     ----      --------     ----
Total Sources of Funds             $542,974                $403,316                $537,227               $394,995
                                   ========    ====        ========     ====       ========     ====      ========     ====
Net Yield on Earning Assets                    3.64%                    4.14%                   3.71%                  4.15%
                                   ========    ====        ========     ====       ========     ====      ========     ====
</TABLE>

                                       11
<PAGE>   12
WESTBANK CORPORATION AND SUBSIDIARIES
MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS
(CONTINUED)


CHANGES IN NET INTEREST INCOME

(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                                QUARTER ENDED 06-30-00                SIX MONTHS ENDED 06-30-00
                                                         OVER                                    OVER
                                                QUARTER ENDED 06-30-99                SIX MONTHS ENDED 06-30-99
                                                     CHANGE DUE TO                           CHANGE DUE TO
                                           VOLUME         RATE        TOTAL       VOLUME         RATE         TOTAL
                                           ------         ----        -----       ------         ----         -----
<S>                                        <C>          <C>          <C>         <C>           <C>           <C>
Interest Income:
      Loans                                $2,219         $125       $2,344       $4,887         $148        $5,035
      Securities                              511          101          612          664          199           863
      Federal funds                           (13)           6           (7)                       23            23
                                            -----          ---        -----        -----          ---         -----
Total Interest Earned                       2,717          232        2,949        5,551          370         5,921
                                            -----          ---        -----        -----          ---         -----
Interest Expense:
      Interest-bearing deposits             1,204          225        1,429        2,404          293         2,697
      Other borrowed funds                    519          236          755        1,016          441         1,457
                                            -----          ---        -----        -----          ---         -----
Total Interest Expense                      1,723          461        2,184        3,420          734         4,154
                                            -----          ---        -----        -----          ---         -----
Net Interest Income                        $  994        $(229)      $  765       $2,131        $(364)       $1,767
                                           ======        =====       ======       ======        =====        ======
</TABLE>

Net interest earned on a tax equivalent basis increased by $765,000 during the
second quarter of 2000 compared to the second quarter of 1999. For the six-month
period ended June 30, 2000, net interest income increased by $1,767,000 versus
the same period of 1999.

Average earning assets increased by $142,232,000 during the first six months of
2000. The average earning base was $537,227,000 compared to $394,995,000 in the
same period last year.


OPERATING EXPENSES

The components of total operating expenses for the periods and their percentage
of gross income are as follows:
(Dollars amounts in thousands)

<TABLE>
<CAPTION>
                                                    QUARTER ENDED                          SIX MONTHS ENDED
                                            06-30-00            06-30-99             06-30-00            06-30-99
                                            --------            --------             --------            --------
                                       Amount    Percent    Amount   Percent     Amount   Percent    Amount    Percent
                                       ------    -------    ------   -------     ------   -------    ------    -------
<S>                                    <C>       <C>        <C>      <C>         <C>      <C>        <C>       <C>
Salaries and benefits                  $1,920     17.19%    $1,470    18.05%     $3,962    17.98%    $2,967     18.42%
Other non-interest expense              1,509     13.51      1,163    14.28       3,189    14.47      2,273     14.11
Occupancy - net                           332      2.96        306     3.75         686     3.12        614      3.82
                                       ------     -----     ------    -----      ------    -----     ------     -----
Total Operating Expenses               $3,761     33.66%    $2,939    36.08%     $7,837    35.57%    $5,854     36.35%
                                       ======     =====     ======    =====      ======    =====     ======     =====
</TABLE>

For the six-month period ended June 30, 2000, operating expenses increased by
approximately $1,983,000 over the 1999 period. The increase was a result of
increases in salary and benefits totaling $995,000, occupancy expense totaling
$72,000 and an increase in other non-interest expense of $916,000. The increases
are a direct result of the branch acquisition on October 29, 1999 and the
related staffing and acquisition costs.

                                       12
<PAGE>   13
WESTBANK CORPORATION AND SUBSIDIARIES
MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS
(CONTINUED)

<TABLE>
<CAPTION>
CAPITAL RATIOS
                                                                     06-30-00              06-30-99
                                                                     --------              --------
<S>                                                                  <C>                   <C>
Ratio of "Tier 1" leverage capital
      to total assets at end of period                                6.23%                  7.34%
</TABLE>

Regulatory risk-based capital requirements take into account the different risk
categories of banking organizations by assigning risk weight to assets and the
credit equivalent amounts of off-balance sheet exposures.

In addition, capital is divided into two tiers. For this Corporation, Tier 1
includes the common stockholders' equity. Tier 2, or supplementary capital,
includes not only the equity but, also, a portion of the allowance for loan
losses. Net unrealized gain/(losses) on securities available for sale are not
permitted to be included for regulatory capital purposes.

The following are the Corporation's risk-based capital ratios at June 30, 2000:

           Tier 1 Capital (minimum required 4.00%)   9.46%
           Tier 2 Capital (minimum required 8.00%)  12.03%

INTEREST RATE SENSITIVITY

The following table sets forth the distribution of the repricing of the
Corporation's earning assets and interest-bearing liabilities as of June 30,
2000.

(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                      Three          Over Three        Over One
                                     Months           Months to         Year to           Over
                                    or Less           One Year        Five Years        Five Years           Total
                                    -------           --------        ----------        ----------           -----
<S>                                <C>               <C>              <C>               <C>                <C>
Earning Assets                     $  71,171         $  59,513          $167,720         $252,510          $550,914
Interest-Bearing
      Liabilities                    169,429           145,100           165,137           17,000           496,666
                                     -------           -------           -------           ------           -------
Interest Rate
      Sensitivity Gap               $(98,258)         $(85,587)         $  2,583         $235,510          $ 54,248
                                     -------           -------           -------           ------           -------
Cumulative Interest
      Rate
      Sensitivity Gap               $(98,258)        $(183,845)        $(181,262)       $  54,248

Interest Rate
      Sensitivity
      Gap Ratio                       (17.84)%          (15.54)%            0.47%           42.75%

Cumulative Interest
      Rate Sensitivity
      Gap Ratio                       (17.84)%          (33.38)%         (32.91)%            9.84%
</TABLE>

                                       13
<PAGE>   14
WESTBANK CORPORATION AND SUBSIDIARIES
MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS
(CONTINUED)


LIQUIDITY

Liquidity management requires close scrutiny of the mix and maturity of deposits
and borrowings and short-term investments. Cash and due from banks, federal
funds sold, investment securities and mortgage-backed securities, as compared to
deposits, are used by Westbank to compute its liquidity on a daily basis as
adjusted for regulatory purposes. In addition, Westbank is subject to Regulation
D of the Federal Reserve Bank (FRB), which requires depository institutions to
maintain reserve balances on deposit with the FRB based on certain average
depositor balances. Westbank is in compliance with Regulation D. Management of
Westbank believes that its current liquidity is sufficient to meet current and
anticipated funding needs.

PROVISION AND ALLOWANCE FOR LOAN LOSSES

(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                                  QUARTER ENDED            SIX MONTHS ENDED
                                              06-30-00     06-30-99      06-30-00      06-30-99
                                              --------     --------      --------      --------
<S>                                           <C>          <C>          <C>           <C>
Balance at beginning of period                 $3,820       $2,669        $3,908       $2,665
Provision charged to expense                       75            2           140           77
                                               ------       ------        ------       ------
                                                3,895        2,671         4,048        2,742
                                               ------       ------        ------       ------
Charge-offs:
      Loans secured by real estate                                           138
      Commercial and industrial loans              19                         31           87
      Consumer loans                               15           22            24           40
                                               ------       ------        ------       ------
                                                   34           22           193          127
                                               ------       ------        ------       ------
Recoveries:
      Loans secured by real estate                 22           70            22           86
      Commercial and industrial loans               9                          9           15
      Consumer loans                                4            2            10            5
                                               ------       ------        ------       ------
                                                   35           72            41          106
                                               ------       ------        ------       ------
Net charge-offs (recoveries)                       (1)         (50)          152           21
                                               ------       ------        ------       ------
Balance at end of period                       $3,896       $2,721        $3,896       $2,721
                                               ------       ------        ------       ------
Net charge-offs to:
      Average loans                               .00%        (.02)%         .03%         .01%
      Loans at end of period                      .00%        (.01)%         .03%         .01%
      Allowance for loan losses                   .00%       (1.84)%        3.90%         .77%

Allowance for loan losses as a percentage of:
           Average loans                          .88%         .82%          .88%         .85%
           Loans at end of period                 .87%         .80%          .87%         .80%
</TABLE>

The approach the Corporation uses in determining the adequacy of the allowance
for loan losses is the combination of a target reserve and a general reserve
allocation. Quarterly, based on an internal review of the loan portfolio, the
Corporation identifies required reserve allocations targeted to recognized
problem loans that, in the opinion of management, have potential loss exposure
or questions relative to the depth of the collateral on these same loans. In
addition, the Corporation allocates a general reserve against the remainder of
the loan portfolio.

                                       14
<PAGE>   15
WESTBANK CORPORATION AND SUBSIDIARIES
NON-ACCRUAL, PAST DUE AND RESTRUCTURED LOANS



<TABLE>
<CAPTION>
(Dollar amounts in thousands)

                                           06-30-00       03-31-00       12-31-99       09-30-99       06-30-99
                                           --------       --------       --------       --------       --------
<S>                                        <C>            <C>            <C>            <C>            <C>
Non-Accrual Loans                            $  691         $  996         $2,001         $  658         $  595
                                             ------         ------         ------         ------         ------
Loans contracturally past
      due 90 days or more
      and still accruing                        778            381            438            357            245
                                             ------         ------         ------         ------         ------
Total non-accrual, past due
      and restructured loans                 $1,469         $1,377         $2,439         $1,015         $  840
                                             ------         ------         ------         ------         ------
Non-accrual, past due and
      restructured loans as a
      percentage of total loans                 .33%           .31%           .55%           .29%           .25%
                                             ------         ------         ------         ------         ------
Allowance for loan losses as a
      percentage of non-accrual,
      past due and restructured loans        265.21%        277.41%        160.23%        262.27%        323.93%
                                             ------         ------         ------         ------         ------

Other real estate owned - net                $  672         $  512         $  442         $   84         $   85
                                             ------         ------         ------         ------         ------

Total non-performing assets                  $2,141         $1,889         $2,881         $1,099         $  925
                                             ------         ------         ------         ------         ------

Non-performing assets as a
      percentage of total assets                .36%           .33%           .50%           .24%           .21%
                                             ------         ------         ------         ------         ------
</TABLE>

                                       15
<PAGE>   16
WESTBANK CORPORATION AND SUBSIDIARIES
QUARTER-TO-DATE AVERAGE BALANCES
INTEREST EARNED - INTEREST EXPENSE


(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                           FOR THE QUARTER ENDED                      FOR THE QUARTER ENDED
                                               JUNE 30, 2000                              JUNE 30, 1999
                                    Balance      Interest      Rate            Balance       Interest      Rate
<S>                               <C>            <C>          <C>             <C>           <C>           <C>
Federal funds sold and
      temporary investments       $    1,933     $    28       5.79%          $    2,849     $     35      4.91%
Securities                            96,242       1,726       7.17               67,374        1,114      6.61
Loans                                444,799       8,848       7.96              333,093        6,504      7.81
                                     -------       -----       ----              -------        -----      ----
Total earning assets                $542,974     $10,602       7.81%             403,316       $7,653      7.59%%
                                     -------       -----       ----              -------        -----      ----
Loan loss allowance                   (3,982)                                     (2,746)
All other assets                      39,708                                      22,916
                                     -------       -----       ----              -------        -----      ----
TOTAL ASSETS                        $578,700                                    $423,486
                                     =======       =====       ====              =======        =====      ====
LIABILITIES AND EQUITY

Interest-bearing deposits           $424,377      $4,659       4.39%            $313,686       $3,230      4.12%
Borrowed funds                        60,747       1,006       6.62               25,031          251      4.01
                                     -------       -----       ----              -------        -----      ----
Total interest-bearing liabilities   485,124       5,665       4.67              338,717       $3,481      4.11
                                     -------       -----       ----              -------        -----      ----
Interest rate spread                                           3.14%                                       3.48%

Demand deposits                       59,733                                      52,032
Other liabilities                      2,672                                       1,617
Shareholders' equity                  31,171                                      31,120
                                     -------       -----       ----              -------        -----      ----
TOTAL LIABILITIES
      AND EQUITY                    $578,700                                    $423,486
                                     =======       =====       ====              =======        =====      ====
NET INTEREST INCOME                               $4,937                                       $4,172
                                     =======       =====       ====              =======        =====      ====
Interest Earned/Earning Assets                                 7.81%                                       7.59%

Interest Expense/Earning Assets                                4.17                                        3.45
                                     -------       -----       ----              -------        -----      ----
Net Yield on Earning Assets                                    3.64%                                       4.14%
                                     -------       -----       ----              -------        -----      ----
Deduct Tax Equivalent Adjustment                      36                                            0
                                     -------       -----       ----              -------        -----      ----
NET INTEREST INCOME                               $4,901                                       $4,172
                                     =======       =====       ====              =======        =====      ====
</TABLE>

                                       16
<PAGE>   17
WESTBANK CORPORATION AND SUBSIDIARIES
YEAR-TO-DATE AVERAGE BALANCES
INTEREST EARNED - INTEREST EXPENSE


(Dollar amounts in thousands)


<TABLE>
<CAPTION>
                                            SIX MONTHS ENDED                      SIX MONTHS ENDED
                                             JUNE 30, 2000                          JUNE 30, 1999
                                    Balance     Interest       Rate        Balance     Interest       Rate
                                    -------     --------       ----        -------     --------       ----
<S>                               <C>          <C>            <C>        <C>          <C>            <C>
Federal funds sold and
      temporary investments       $    3,483   $      96       5.51%     $    3,374    $      73      4.33%
Securities                            91,208       3,253       7.13          72,321        2,390      6.61
Loans                                442,536      17,568       7.94         319,300       12,533      7.85
                                     -------      ------       ----         -------       ------      ----
Total earning assets                 537,227     $20,917       7.79%        394,995      $14,996      7.59%
                                     -------      ------       ----         -------       ------      ----
Loan loss allowance                   (3,990)                                (2,714)
All other assets                      39,298                                 22,766
                                     -------      ------       ----         -------       ------      ----
TOTAL ASSETS                        $572,535                               $415,047
                                     =======     =======       ====         =======      =======      ====
LIABILITIES AND EQUITY

Interest-bearing deposits           $419,341    $  9,007       4.26%       $306,696       $6,310      4.11%
Borrowed funds                        60,577       1,953       6.45          24,944          496      3.98
                                     -------      ------       ----         -------       ------      ----
Total interest-bearing
      liabilities                    479,918      10,960       4.57         331,640       $6,806      4.10
                                     -------      ------       ----         -------       ------      ----
Interest rate spread                                           3.22%                                  3.49%

Demand deposits                       58,925                                 50,627
Other liabilities                      2,517                                  1,782
Shareholders' equity                  31,175                                 30,998
                                     -------      ------       ----         -------       ------      ----
TOTAL LIABILITIES
      AND EQUITY                    $572,535                               $415,047
                                     =======     =======       ====         =======      =======      ====
NET INTEREST INCOME                               $9,957                                  $8,190
                                     =======     =======       ====         =======      =======      ====
Interest Earned/Earning Assets                                 7.79%                                  7.59%

Interest Expense/Earning Assets                                4.08                                   3.44
                                     -------      ------       ----         -------       ------      ----
Net Yield on Earning Assets                                    3.71%                                  4.15%
                                     -------      ------       ----         -------       ------      ----
Deduct Tax Equivalent Adjustment                      68                                       0
                                     -------      ------       ----         -------       ------      ----
NET INTEREST INCOME                               $9,889                                  $8,190
                                     =======     =======       ====         =======      =======      ====
</TABLE>

                                       17
<PAGE>   18
WESTBANK CORPORATION AND SUBSIDIARIES
PART II  -  OTHER INFORMATION


ITEM 1.         Legal Proceedings  -  NONE

ITEM 2.         Changes in Rights of Securities Holders  -  NONE

ITEM 3.         Defaults by Company on its Senior Securities  -  NONE

ITEM 4.         Results of Votes on Matters Submitted to a Vote of Security
                Holders  -  NONE

ITEM 5.         Other Events

     a.         Information Concerning Forward-Looking Statements

                Westbank has made, and may make in the future, forward-looking
                statements concerning future performance, including, but not
                limited to, future earnings and events or conditions that may
                affect such future performance. These forward-looking statements
                are based upon management's expectations and belief concerning
                possible future developments and the potential effect of such
                future developments on Westbank. There is no assurance that such
                future developments will be in accordance with management's
                expectations and belief or that the effect of any future
                developments on Westbank will be those anticipated by Westbank
                management.

                All assumptions that form the basis of any forward-looking
                statements regarding future performance, as well as events or
                conditions that may affect such future performance, are based on
                factors that are beyond Westbank's ability to control or predict
                with precision, including future market conditions and the
                behavior of other market participants. Among the factors that
                could cause actual results to differ materially from such
                forward-looking statements are the following:

                1.    The status of the economy in general, as well as in
                      Westbank's prime market areas of Western Massachusetts and
                      Northeastern Connecticut;

                2.    The real estate market in Western Massachusetts and
                      Northeastern Connecticut;

                3.    Competition in Westbank's prime market area from other
                      banks, especially in light of continued consolidation in
                      the New England banking industry;

                4.    Any changes in federal and state bank regulatory
                      requirements;

                5.    Changes in interest rates; and

                6.    The cost and other effects of unanticipated legal and
                      administrative cases and proceedings, settlements and
                      investigations.

                While Westbank periodically reassesses material trends and
                uncertainties affecting the Corporation's performance in
                connection with its preparation of Management's Discussion and
                Analysis of Results of Operations and Financial Condition
                contained in its quarterly and annual reports, Westbank does not
                intend to review or revise any particular forward-looking
                statements.

      b.        Registration on Form S-3

                None.

      c.        Registration of Form S-8

                None

                                       18
<PAGE>   19
ITEM 6.         Exhibits and Reports on Form 8

                a.    Exhibits

                                  EXHIBIT INDEX

<TABLE>
<CAPTION>
                                                                                                     Page No.
                                                                                                     --------
<S>                                                                                                 <C>
      3.        Articles of Organization, as amended                                                    **

                (a)  Articles of Organization, as amended                                                *

                (b)  By-Laws, as amended                                                                 *

      10.       Material Contracts  -  None

      27.       Financial Data Schedule                                                              To be included
</TABLE>


      *         Incorporated by reference to identically numbered exhibits
                contained in Registrant's Annual Report on Form 10-K for the
                year ended December 31, 1988.

      **        Incorporated by reference to identically numbered exhibits
                contained in Registrant's Annual Report on Form 10-K for the
                year ended December 31, 1987.

      b.        Reports on Form 8-K  -  None


                                       19
<PAGE>   20
WESTBANK CORPORATION AND SUBSIDIARIES



Pursuant to the requirements of the Securities Exchange Act of 1934, the
Registrant has duly caused this Quarterly Report to be signed on its behalf by
the undersigned thereunto duly authorized.





                                          WESTBANK CORPORATION





Date:    August 11, 2000
                                          --------------------------------------
                                          Donald R. Chase
                                          President and Chief Executive Officer





Date:    August 11, 2000
                                          --------------------------------------
                                          John M. Lilly
                                          Treasurer and Chief Financial Officer


                                       20