<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 SEPTEMBER 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 per share: 4,226,593 shares outstanding as of
                                      October 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)                               September 30, 2000     December 31, 1999
                                                            ------------------     -----------------
<S>                                                         <C>                    <C>
ASSETS
Cash and due from banks:
      Non-interest bearing                                           $  15,609             $  17,006
      Interest bearing                                                     270                 1,147
Federal funds sold                                                         896                13,389
                                                                     ---------             ---------
Total cash and cash equivalents                                         16,775                31,542
                                                                     ---------             ---------
Investment securities available for sale                                87,491                69,516
Investment securities held to maturity
      (fair value of $11,308 in 2000 and $11,652 in 1999)               11,498                11,804
                                                                     ---------             ---------
Total securities                                                        98,989                81,320
                                                                     ---------             ---------
Loans                                                                  448,366               440,319
Mortgage loans held-for-sale                                             1,865                 2,156
Allowance for loan losses                                               (3,460)               (3,908)
                                                                     ---------             ---------
      Net loans                                                        446,771               438,567
Bank premises and equipment                                              7,384                 7,809
Other real estate owned                                                    605                   442
Accrued interest receivable                                              4,018                 3,243
Intangible assets                                                        9,672                 9,971
Other assets                                                             3,839                 3,256
                                                                     ---------             ---------
TOTAL ASSETS                                                         $ 588,053             $ 576,150
                                                                     =========             =========
LIABILITIES AND STOCKHOLDERS' EQUITY
Deposits:
      Non-interest bearing                                           $  62,710             $  59,643
      Interest bearing                                                 437,618               419,253
                                                                     ---------             ---------
      Total deposits                                                   500,328               478,896
Borrowed funds                                                          34,651                46,546
Accrued interest payable                                                 1,118                   732
Other liabilities                                                        1,901                 1,433
                                                                     ---------             ---------
      Total liabilities                                                537,998               527,607
                                                                     ---------             ---------
Mandatory redeemable preferred stock                                    17,000                17,000
                                                                     ---------             ---------
Stockholders' Equity:
      Common stock       --   $2 par value
           Authorized    --   9,000,000 shares
           Issued        --   4,283,719 shares in 2000 and
                              4,283,719 shares in 1999                   8,567                 8,567
      Additional paid in capital                                        11,621                11,633
      Retained earnings                                                 14,860                13,317
      Treasury stock - 73,050 shares                                      (638)
      Accumulated other comprehensive income (loss)                     (1,355)               (1,974)
                                                                     ---------             ---------
           Total Stockholders' Equity                                   33,055                31,543
                                                                     ---------             ---------
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY                           $ 588,053             $ 576,150
                                                                     =========             =========
</TABLE>

     See accompanying notes to condensed consolidated financial statements.



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

(Unaudited)
(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                                   QUARTER ENDED                     NINE MONTHS ENDED
                                             09-30-00          09-30-99          09-30-00          09-30-99
                                            ----------        ----------        ----------        ----------
<S>                                         <C>               <C>               <C>               <C>
Income:
      Interest and fees on loans            $    8,944        $    6,749        $   26,451        $   19,282
      Interest on federal funds sold               101                28               197               101
      Interest on securities                     1,794             1,177             5,040             3,567
                                            ----------        ----------        ----------        ----------
                                                10,839             7,954            31,688            22,950
Interest expense                                 6,192             3,697            17,152            10,503
                                            ----------        ----------        ----------        ----------
Net interest income                              4,647             4,257            14,536            12,447
Provision for loan losses                           13                 0               153                77
                                            ----------        ----------        ----------        ----------
Net interest income after provision              4,634             4,257            14,383            12,370
                                            ----------        ----------        ----------        ----------
Realized investment gains                            0                 0                 0                92
Other non-interest income                          555               602             1,739             1,620
                                            ----------        ----------        ----------        ----------
Total non-interest income                          555               602             1,739             1,712
                                            ----------        ----------        ----------        ----------
Operating expense:
      Salaries and benefits                      1,976             1,581             5,938             4,548
      Other operating expenses                   1,667             1,114             4,856             3,387
      Occupancy - net                              339               294             1,025               908
                                            ----------        ----------        ----------        ----------
Total operating expenses                         3,982             2,989            11,819             8,843
                                            ----------        ----------        ----------        ----------
Income before income taxes                       1,207             1,870             4,303             5,239
Income taxes                                       370               735             1,486             2,012
                                            ----------        ----------        ----------        ----------
Net Income                                  $      837        $    1,135        $    2,817        $    3,227
                                            ==========        ==========        ==========        ==========

Earnings per share
          --   Basic                        $     0.20        $     0.27        $     0.67        $     0.76
          --   Diluted                      $     0.20        $     0.26        $     0.66        $     0.75
Weighted average shares outstanding
          --   Basic                         4,206,430         4,260,321         4,230,001         4,232,378
          --   Dilutive option shares           38,861            95,546            48,675            98,593
          --   Diluted                       4,245,291         4,355,867         4,278,676         4,330,971
</TABLE>

     See accompanying notes to condensed consolidated financial statements.



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



(Unaudited)
(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                                              QUARTER ENDED                  NINE MONTHS ENDED
                                                       09-30-00         09-30-99         09-30-00          09-30-99
                                                       -------          -------           -------          -------
<S>                                                    <C>              <C>               <C>              <C>
Net Income                                             $   837          $ 1,135           $ 2,817          $ 3,227
                                                       -------          -------           -------          -------
Other comprehensive income:

      Unrealized gain/(loss) on securities
      available for sale, net of income taxes
      (benefits) of $333 and $(254) for the
      quarter and $342 and $(996) for the
      nine-month periods ended September 30,
      2000 and 1999, respectively                          741             (410)              619           (1,606)

      Reclassification adjustment for
      gains included in net income,
      net of income taxes of $35 for
      the nine-month period ended
      September 30, 1999                                                                                        57
                                                       -------          -------           -------          -------

Other comprehensive income (loss)                          741             (410)              619           (1,549)
                                                       -------          -------           -------          -------

Comprehensive Income                                   $ 1,578          $   725           $ 3,436          $ 1,678
                                                       =======          =======           =======          =======
</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 NINE MONTHS ENDED SEPTEMBER 30, 2000


(2000 unaudited)
(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                                                                                         ACCUMULATED
                                     COMMON STOCK                                                           OTHER
                                  --------------------    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                                                                  2,817                                         2,817
Cash dividend declared
  ($.30 per share)                                                         (1,274)                                       (1,274)

Treasury Shares:
  Redeemed                         (123,200)                                             $(1,097)                        (1,097)
  Reissued                           50,150                    (12)                          459                            447
Changes in unrealized loss on
  securities available for sale                                                                                619          619
                                  ---------     ------     -------        -------         ------           -------      -------
BALANCE - SEPTEMBER 30, 2000      4,210,669     $8,567     $11,621        $14,860         $ (638)          $(1,355)     $33,055
                                  =========     ======     =======        =======         ======           =======      =======
</TABLE>

     See accompanying notes to condensed consolidated financial statements.

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

(Unaudited)
(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                                                                     2000                 1999
                                                                                   --------             --------
<S>                                                                                <C>                  <C>
Operating activities:
      Net income                                                                   $  2,817             $  3,227
           Adjustments to reconcile net income to
           net cash provided by operating activities:
                Provision for loan losses                                               153                   77
                Provision for other real estate owned                                    62
                Depreciation and amortization                                           788                  729
                Intangible amortization                                                 457
                Realized gain on sale of securities                                                          (92)
                Realized gain/(loss) on sale of other real estate owned                 (50)                  19
           Changes in assets and liabilities:
                (Increase)/Decrease in accrued interest receivable                     (775)                (188)
                Increase/(Decrease) in interest payable on deposits                     386                   97
                (Increase)/Decrease in other assets                                    (915)              (1,467)
                Increase/(Decrease) in other liabilities                                691                 (437)
                                                                                   --------             --------
                Net cash provided by operating activities                             3,614                1,965
                                                                                   --------             --------
Investing activities:
      Investments and mortgage-backed securities:
           Held to maturity:
                Purchases                                                                                 (1,050)
                Proceeds from maturities and principal payments                         306               19,762
           Available for sale:
                Purchases                                                           (21,389)             (21,608)
                Proceeds from sales                                                                        4,679
                Proceeds from maturities                                              4,424               12,271
      Purchases of premises and equipment                                              (363)              (1,328)
      Net (increase) in loans                                                        (8,834)             (59,512)
      Proceeds from sale of other real estate owned                                      85                  382
                                                                                   --------             --------
           Net cash used in investing activities                                    (25,771)             (46,404)
                                                                                   --------             --------
Financing activities:
      Net increase/(decrease) in other borrowed funds                               (12,118)               8,570
      Net increase/(decrease) in deposits                                            21,432               38,362
      Proceeds from mandatory redeemable preferred stock                                                  17,000
      Proceeds from exercise of stock options and stock purchase plan                                        578
      Treasury stock (purchased)/issued, net                                           (650)
      Dividends paid                                                                 (1,274)              (1,226)
                                                                                   --------             --------
           Net cash provided by financing activities                                  7,390               63,284
                                                                                   --------             --------
Increase/(Decrease) in cash and cash equivalents                                    (14,767)              18,845
Cash and cash equivalents at beginning of period                                     31,542               14,240
                                                                                   --------             --------
Cash and cash equivalents at end of period                                         $ 16,775             $ 33,085
                                                                                   ========             ========
Cash paid during the period:
      Interest on deposits and other borrowings                                    $ 16,766             $ 10,406
      Income taxes                                                                    1,222                1,874
Transfers of loans to other real estate owned                                           357
</TABLE>

     See accompanying notes to condensed consolidated financial statements.



                                       7
<PAGE>   8
WESTBANK CORPORATION AND SUBSIDIARIES
NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
QUARTER AND NINE MONTHS ENDED SEPTEMBER 30, 2000 AND SEPTEMBER 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 four 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 September 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 nine months ended September 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
nine-month period ended September 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 nine months ended
September 30, 1999, as if this acquisition had occurred at the beginning of
1999, were as follows:

<TABLE>
<CAPTION>
                                                  Quarter             Nine Months
                                                  -------             -----------
<S>                                               <C>                   <C>
           Net interest income                    $5,114                $15,024
           Net income                             $1,171                $ 3,265
           Basic earnings per share                $0.27                  $0.77
           Diluted earnings per share              $0.27                  $0.75
</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 September 30, 2000, standby letters of credit amounted to
$751,000 and loan commitments were $34,500,000 and unused balances available on
home equity lines of credit were $11,334,000.

Trust Assets - Property with a book value of $117,056,000 at September 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 September 30, 2000 were as
follows:

<TABLE>
<CAPTION>
                                                    Park West Bank
                                                  and Trust Company      Cargill Bank
                                                  -----------------      ------------
<S>                                               <C>                    <C>
      Leverage Capital Ratio                             7.18%               6.13%
      Tier 1 Risk-Based Capital                         10.87%              11.26%
      Total Risk-Based Capital                          11.75%              12.43%
</TABLE>

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


NOTE G  -  NEW ACCOUNTING STANDARDS

The Financial Accounting Standards Board (the "FASB") issued SFAS No. 133,
Accounting for Derivative Instruments and Hedging Activities. This statement
established accounting and reporting standards for derivative instruments
including derivative activities. This statement will be effective for the
Corporation's 2001 financial statements. The Corporation has not determined the
effect of this standard on its financial statements.



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



Changes in Financial Condition

Total consolidated assets amounted to $588,053,000 on September 30, 2000,
compared to $576,150,000 on December 31, 1999. As of September 30, 2000 and
December 31, 1999, earning assets amounted to, respectively, $550,386,000 or 94%
of total assets and $538,331,000 or 93% of total assets. Earning assets
increased during the first nine 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 September 30, 2000, net income totaled $837,000, compared
to $1,135,000 for the quarter ended September 30, 1999. For the nine months
ended September 30, 2000, net income was $2,817,000, compared to $3,227,000 for
the same period during 1999. Included in the results for the nine months ended
September 30, 2000 were approximately $250,000 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 $13,000,
compared to $0 for the same period in 1999. Loans written off against the
allowance for loan losses after recoveries amounted to $601,000 for the nine
months ended September 30, 2000.

After giving effect to the actions described above, the allowance for loan
losses at September 30, 2000, totaled $3,460,000 or .77% of total loans, as
compared to $3,908,000 or .89% at December 31, 1999.

Non-performing past due loans at September 30, 2000, aggregated $2,057,000 or
 .46% 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 .35% 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 September 30, 2000, totaled $605,000 and stands at
 .10% 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
                                       09-30-00    09-30-99     09-30-00     09-30-99
                                       -------      -------      -------      -------
<S>                                    <C>         <C>          <C>          <C>
     Interest and dividend income      $10,839      $ 7,954      $31,688      $22,950
     Interest expense                    6,192        3,697       17,152       10,503
                                       -------      -------      -------      -------
     Net interest income               $ 4,647      $ 4,257      $14,536      $12,447
                                       =======      =======      =======      =======
</TABLE>

INTEREST RATE SPREAD AND NET YIELD ON EARNING ASSETS

(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                        QUARTER ENDED SEPTEMBER 30,                   NINE MONTHS ENDED SEPTEMBER 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                 $556,944        7.82%      $ 419,637    7.58%      $543,794     7.80%    $403,205       7.59%
                               --------        ----       ---------    ----       --------     ----     --------       ----
Interest-bearing
      liabilities               497,680        4.98         354,474    4.17        485,838     4.71      339,252       4.13
                               --------        ----       ---------    ----       --------     ----     --------       ----
Interest rate spread                           2.84                    3.41                    3.09                    3.46
                                               ----                    ----                    ----                    ----
Interest-free resources
      used to fund
      earning assets             59,264                      65,163                 57,956                63,953
                               --------                   ---------               --------              --------
Total Sources of Funds         $556,944                   $ 419,637               $543,794              $403,205
                               ========                   =========               ========              ========
Net Yield on Earning Assets                    3.37%                   4.06%                   3.59%                   4.12%
                                               ====                    ====                    ====                    ====
</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 09-30-00                      NINE MONTHS ENDED 09-30-00
                                                       OVER                                          OVER
                                               QUARTER ENDED 09-30-99                      NINE MONTHS ENDED 09-30-99
                                       --------------------------------------        --------------------------------------
                                                   CHANGE DUE TO                                 CHANGE DUE TO
                                        VOLUME         RATE            TOTAL         VOLUME          RATE            TOTAL
                                       -------        -------         -------        -------        -------         -------
<S>                                    <C>         <C>                <C>            <C>         <C>                <C>
Interest Income:
      Loans                            $ 2,050        $   187         $ 2,237        $ 6,937        $   335         $ 7,272
      Securities                           533             88             621          1,197            287           1,484
      Federal funds                         66              7              73             66             30              96
                                       -------        -------         -------        -------        -------         -------
Total Interest Earned                    2,649            282           2,931          8,200            652           8,852
                                       -------        -------         -------        -------        -------         -------
Interest Expense:
      Interest-bearing deposits          1,434            556           1,990          3,838            849           4,687
      Other borrowed funds                 337            168             505          1,353            609           1,962
                                       -------        -------         -------        -------        -------         -------
Total Interest Expense                   1,771            724           2,495          5,191          1,458           6,649
                                       -------        -------         -------        -------        -------         -------
Net Interest Income                    $   878        $  (442)        $   436        $ 3,009        $  (806)        $ 2,203
                                       =======        =======         =======        =======        =======         =======
</TABLE>

Net interest earned on a tax equivalent basis increased by $436,000 during the
third quarter of 2000 compared to the third quarter of 1999. For the nine-month
period ended September 30, 2000, net interest income increased by $2,203,000
versus the same period of 1999.

Average earning assets increased by $140,589,000 during the first nine months of
2000. The average earning base was $543,794,000 compared to $403,205,000 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                         NINE MONTHS ENDED
                                  09-30-00            09-30-99             09-30-00             09-30-99
                              -------------------------------------     -------------------------------------
                               Amount   Percent    Amount    Percent    Amount    Percent    Amount    Percent
                               ------   -------    ------    -------    ------    -------    ------    --------
<S>                           <C>       <C>        <C>       <C>        <C>       <C>        <C>       <C>
Salaries and benefits         $ 1,976    17.34%    $ 1,581    18.48%    $ 5,938    17.76%    $ 4,548    18.44%
Other non-interest expense      1,667    14.63       1,114    13.02       4,856    14.53       3,387    13.73
Occupancy - net                   339     2.98         294     3.43       1,025     3.07         908     3.69
                              -------    -----     -------    -----     -------    -----     -------    -----
Total Operating Expenses      $ 3,982    34.95%    $ 2,989    34.93%    $11,819    35.36%    $ 8,843    35.86%
                              =======    =====     =======    =====     =======    =====     =======    =====
</TABLE>

For the nine-month period ended September 30, 2000, operating expenses increased
by approximately $2,976,000 over the 1999 period. The increase was a result of
increases in salary and benefits totaling $1,390,000, occupancy expense totaling
$117,000 and an increase in other non-interest expense of $1,469,000. 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)



CAPITAL RATIOS

<TABLE>
<CAPTION>
                                                  09-30-00              09-30-99
                                                  --------              --------
<S>                                               <C>                   <C>
Ratio of "Tier 1" leverage capital
      to total assets at end of period              6.20%                 9.70%
</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 September 30,
2000:

           Tier 1 Capital (minimum required 4.00%)     9.46 %
           Tier 2 Capital (minimum required 8.00%)    11.81 %

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 September
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                $  67,401          $  66,843          $ 170,444          $ 245,698         $ 550,386
Interest-Bearing
      Liabilities               121,584            170,123            179,895             17,667           489,269
                              ---------          ---------          ---------          ---------         ---------
Interest Rate
      Sensitivity Gap         $ (54,183)         $(103,280)         $  (9,451)         $ 228,031         $  61,117
                              ---------          ---------          ---------          ---------         ---------
Cumulative Interest
      Rate
      Sensitivity Gap         $ (54,183)         $(157,463)         $(166,914)         $  61,117

Interest Rate
      Sensitivity
      Gap Ratio                   (9.84)%           (18.77)%            (1.72)%           41.44%

Cumulative Interest
      Rate Sensitivity
      Gap Ratio                   (9.84)%           (28.61)%           (30.33)%           11.11%
</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              NINE MONTHS ENDED
                                                    09-30-00       09-30-99       09-30-00       09-30-99
                                                     ------         ------         ------         ------
<S>                                                 <C>            <C>            <C>            <C>
Balance at beginning of period                       $3,896          $2721         $3,908         $2,665
Provision charged to expense                             13                           153             77
                                                     ------         ------         ------         ------
                                                      3,909          2,721          4,061          2,742
                                                     ------         ------         ------         ------
Charge-offs:
      Loans secured by real estate                       25             41            163            128
      Commercial and industrial loans                   410                           441
      Consumer loans                                     29             25             53             65
                                                     ------         ------         ------         ------
                                                        464             66            657            193
                                                     ------         ------         ------         ------
Recoveries:
      Loans secured by real estate                        9              4             31             90
      Commercial and industrial loans                     1                            10             15
      Consumer loans                                      5              3             15              8
                                                     ------         ------         ------         ------
                                                         15              7             56            113
                                                     ------         ------         ------         ------
Net charge-offs (recoveries)                            449             59            601             80
                                                     ------         ------         ------         ------
Balance at end of period                             $3,460         $2,662         $3,460         $2,662
                                                     ======         ======         ======         ======
Net charge-offs to:
      Average loans                                    0.10%          0.02%          0.13%          0.02%
      Loans at end of period                           0.10%          0.02%          0.13%          0.02%
      Allowance for loan losses                       12.98%          2.21%         17.37%          3.01%

Allowance for loan losses as a percentage of:
           Average loans                               0.77%          0.77%          0.78%          0.81%
           Loans at end of period                      0.77%          0.75%          0.77%          0.75%
</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
(CONTINUED)



(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                            09-30-00       06-30-00       03-31-00       12-31-99       09-30-99
                                            --------       --------       --------       --------       --------
<S>                                         <C>            <C>            <C>            <C>            <C>
Non-Accrual Loans                            $1,693         $  691         $  996         $2,001         $  658
                                             ------         ------         ------         ------         ------
Loans contracturally past
      due 90 days or more
      and still accruing                        364            778            381            438            357
                                             ------         ------         ------         ------         ------
Total non-accrual, past due
      and restructured loans                 $2,057         $1,469         $1,377         $2,439         $1,015
                                             ------         ------         ------         ------         ------
Non-accrual, past due and
      restructured loans as a
      percentage of total loans                 .46%           .33%           .31%           .55%           .29%
                                             ------         ------         ------         ------         ------
Allowance for loan losses as a
      percentage of non-accrual,
      past due and restructured loans        168.21%        265.21%        277.41%        160.23%        262.27%
                                             ------         ------         ------         ------         ------
Other real estate owned - net                $  605         $  672         $  512         $  442         $   84
                                             ------         ------         ------         ------         ------
Total non-performing assets                  $2,662         $2,141         $1,889         $2,881         $1,099
                                             ------         ------         ------         ------         ------
Non-performing assets as a
      percentage of total assets                .45%           .36%           .33%           .50%           .24%
                                             ------         ------         ------         ------         ------
</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
                                          SEPTEMBER 30, 2000                         SEPTEMBER 30, 1999
                                     Balance   Interest        Rate             Balance     Interest       Rate
                                   ----------  ---------       ----           ----------    ---------      ----
<S>                               <C>          <C>             <C>            <C>           <C>            <C>
Federal funds sold and
      temporary investments       $    6,493   $     101       6.22%          $    2,167    $      28      5.17%
Securities                            99,627       1,798       7.22               69,797        1,177      6.74
Loans                                450,824       8,986       7.97              347,673        6,749      7.76
                                   ----------  ---------       ----           ----------    ---------      ----
Total earning assets                 556,944      10,885       7.82%             419,637        7,954      7.58%
                                   ----------  ---------       ----           ----------    ---------      ----
Loan loss allowance                   (4,101)                                     (2,717)
All other assets                      40,474                                      23,189
                                   ---------                                  ----------
TOTAL ASSETS                        $593,317                                    $440,109
                                   =========                                  ==========

LIABILITIES AND EQUITY

Interest-bearing deposits           $443,818      $5,293       4.77%            $319,023       $3,303      4.14%
Borrowed funds                        53,862         899       6.68               35,451          394      4.45
                                   ----------  ---------       ----           ----------    ---------      ----

Total interest-bearing
     liabilities                     497,680       6,192       4.98%             354,474        3,697      4.17%
                                   ----------  ---------       ----           ----------    ---------      ----

Interest rate spread                                           2.84%                                       3.41%

Demand deposits                       60,166                                      52,457
Other liabilities                      3,278                                       2,063
Shareholders' equity                  32,193                                      31,115
                                   ----------                                 ----------
TOTAL LIABILITIES
      AND EQUITY                    $593,317                                    $440,109
                                   =========                                  ==========

NET INTEREST INCOME                               $4,693                                       $4,257
                                               =========                                    =========
Interest Earned/Earning Assets                                 7.82%                                       7.58%

Interest Expense/Earning Assets                                4.45                                        3.52
                                                               ----                                        ----
Net Yield on Earning Assets                                    3.37%                                       4.06%
                                                               ----                                        ----
Deduct Tax Equivalent Adjustment                      46                                            0
                                               ---------                                    ---------
NET INTEREST INCOME                               $4,647                                       $4,257
                                               =========                                    =========
</TABLE>

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


(Dollar amounts in thousands)

<TABLE>
<CAPTION>
                                           NINE MONTHS ENDED                         NINE MONTHS ENDED
                                          SEPTEMBER 30, 2000                         SEPTEMBER 30, 1999
                                   Balance     Interest        Rate            Balance      Interest       Rate
                                  ----------  ----------       ----           ----------   ----------      ----
<S>                               <C>         <C>              <C>            <C>          <C>             <C>
Federal funds sold and
      temporary investments       $    4,485  $      197       5.86%          $    2,971   $      101      4.53%
Securities                            94,014       5,051       7.16               71,479        3,567      6.65
Loans                                445,295      26,554       7.95              328,755       19,282      7.82
                                  ----------  ----------       ----           ----------   ----------      ----
Total earning assets                 543,794     $31,802       7.80%             403,205      $22,950      7.59%
                                  ----------  ----------       ----           ----------   ----------      ----

Loan loss allowance                   (4,027)                                     (2,715)
All other assets                      39,841                                      22,909
                                  ----------                                  ----------
TOTAL ASSETS                        $579,608                                    $423,399
                                  ==========                                  ==========
LIABILITIES AND EQUITY

Interest-bearing deposits           $427,500     $14,300       4.46%            $310,806       $9,613      4.12%
Borrowed funds                        58,338       2,852       6.52               28,446          890      4.17
                                  ----------  ----------       ----           ----------   ----------      ----
Total interest-bearing
      liabilities                    485,838     $17,152       4.71              339,252      $10,503      4.13
                                  ----------  ----------       ----           ----------   ----------      ----
Interest rate spread                                           3.09%                                       3.46%

Demand deposits                       59,339                                      51,237
Other liabilities                      2,913                                       1,873
Shareholders' equity                  31,518                                      31,037
                                  ----------                                  ----------
TOTAL LIABILITIES
      AND EQUITY                    $579,608                                    $423,399
                                  ==========                                  ==========

NET INTEREST INCOME                              $14,650                                      $12,447
                                              ==========                                   ==========
Interest Earned/Earning Assets                                 7.80%                                       7.59%

Interest Expense/Earning Assets                                4.21                                        3.47
                                                               ----                                        ----
Net Yield on Earning Assets                                    3.59%                                       4.12%
                                                               ----                                        ----
Deduct Tax Equivalent Adjustment                     114                                            0
                                              ----------                                   ----------

NET INTEREST INCOME                              $14,536                                      $12,447
                                              ==========                                   ==========
</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>                                                             <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:    November 10, 2000                                  /s/
                                           ------------------------------------
                                           Donald R. Chase
                                           President and Chief Executive Officer





Date:    November 10, 2000                                 /s/
                                           ------------------------------------
                                           John M. Lilly
                                           Treasurer and Chief Financial Officer



                                       20