PROSPECTUS


                                 420,989 SHARES
                     COMMON STOCK ($.01 PAR VALUE PER SHARE)
                                NBT BANCORP INC.


         This prospectus relates to the offering by a selling stockholder, David
T. Griffith,  for resale of 420,989  shares of common stock,  $.01 par value per
share of NBT Bancorp  Inc., a Delaware  corporation.  This offering is not being
underwritten.  Mr.  Griffith will receive the entire proceeds of any sales he is
able to make of the shares,  except for brokerage commissions and other costs he
must incur in connection with his sales. We will receive no part of the proceeds
of any sales made by Mr. Griffith.  We have not previously registered any of Mr.
Griffith's  shares of our common  stock prior to the filing of the  Registration
Statement of which this prospectus is a part.


         Our common  stock is quoted on the  Nasdaq  National  Market  under the
symbol "NBTB." On July 5, 2000, the last reported sale price of our common stock
was $10.25 per share.

         Mr.  Griffith  may offer the shares for sale from time to time  through
broker-dealers on the Nasdaq National Market, or otherwise, at such prices as he
is  able to  obtain  at the  time of each  sale.  Mr.  Griffith  and any  broker
executing  selling orders on his behalf may be deemed to be underwriters  within
the  meaning  of  the  Securities  Act  of  1933,  as  amended.   See  "Plan  of
Distribution."

         We encourage you to read this  prospectus  carefully.  This  prospectus
incorporates  important business and financial  information about us that is not
included  in or  delivered  with this  document.  See  "Where  You Can Find More
Information" on page 2.


                  NEITHER  THE SEC  NOR  ANY  STATE  SECURITIES  COMMISSION  HAS
APPROVED OR DISAPPROVED OF THE NBT SHARES TO BE ISSUED UNDER THIS  PROSPECTUS OR
PASSED UPON THE ADEQUACY OR ACCURACY OF THIS PROSPECTUS.  ANY  REPRESENTATION TO
THE CONTRARY IS A CRIMINAL OFFENSE.

         THE  SHARES OF NBT COMMON  STOCK  OFFERED  BY THIS  PROSPECTUS  ARE NOT
SAVINGS  ACCOUNTS,  DEPOSITS  OR  OTHER  OBLIGATIONS  OF ANY  BANK  OR  NON-BANK
SUBSIDIARY OF ANY OF THE PARTIES. THE FDIC OR ANY OTHER GOVERNMENTAL AGENCY DOES
NOT  INSURE OR  GUARANTEE  ANY LOSS TO YOU OF YOUR  INVESTMENT  VALUE IN THE NBT
COMMON STOCK.


                  The date of this prospectus is July 6, 2000



No person has been authorized to give any information or to make any representations other than those contained in or incorporated by reference in this prospectus in connection with the offering made by this prospectus, and, if given or made, such information or representations must not be relied upon as having been authorized by us, the selling stockholder or any other person. Neither the delivery of this prospectus nor any sale made under this prospectus shall, under any circumstances, create an implication that information in this prospectus is correct as of any time subsequent to the date of this prospectus or that there has been no change in our affairs since the date as of which information is given in this prospectus. This prospectus does not constitute an offer to sell or a solicitation of an offer to buy any security other than the securities covered by this prospectus, nor does it constitute an offer to or a solicitation of any person in any jurisdiction in which such offer or solicitation may not be lawfully made. TABLE OF CONTENTS Where You Can Find More Information ...................................... 2 NBT Bancorp Inc. SEC Filings (SEC File No. 0-14703) ..................... 3 NBT Bancorp Inc .......................................................... 3 Use of Proceeds .......................................................... 5 Price Range of Common Stock and Dividends ................................ 5 Selling Stockholder ...................................................... 6 Plan of Distribution ..................................................... 6 Description of NBT Capital Stock ......................................... 7 Legal Matters ............................................................ 8 Experts .................................................................. 8 Cautionary Statement Regarding Forward-Looking Statements ................ 9 Unaudited Pro Forma Condensed Combined Financial Statements .............. 10 Notes to Unaudited Pro Forma Condensed Combined Financial Statements ..... 17 WHERE YOU CAN FIND MORE INFORMATION We file annual, quarterly and special reports, proxy statements and other information with the SEC. You may read and copy any reports, statements or other information we file at the SEC's public reference room at 450 Fifth Street, N.W., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the public reference rooms. Our SEC filings are also available to the public from commercial document retrieval services and at the web site maintained by the SEC at {http://www.sec.gov}. In addition, you may read and copy our SEC filings at the Nasdaq National Market, 1735 K Street, N.W., Washington, D.C. 20006-1500. Our Internet address is {www.nbtbank.com}. We have filed a registration statement on Form S-3 to register with the SEC our common stock being offered and sold by the selling stockholder, Mr. Griffith. This prospectus is a part of that registration statement. As allowed 2

by SEC rules, this prospectus does not contain all the information you can find in the registration statement or the exhibits to the registration statement. The SEC allows us to "incorporate by reference" information into this prospectus, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, except for any information superseded by information in this prospectus. These documents contain important information about our company, our finances and our common stock. NBT BANCORP INC. SEC FILINGS (SEC FILE NO. 0-14703) We incorporate by reference the documents listed below and any future filings that we make with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, between the date of this prospectus and the termination date of this offering. o Annual Report on Form 10-K for the year ended December 31, 1999; o Quarterly Report on Form 10-Q for the quarter ended March 31, 2000; o Current Reports on Form 8-K, filed with the SEC on February 22, 2000, March 3, 2000, March 31, 2000, and April 28, 2000; and o Our SEC Rule 424(b) final prospectus, dated April 3, 2000, with respect to the section captioned "Description of NBT Capital Stock." On March 31, 2000, we filed a Current Report on Form 8-K with the SEC. The report contains our supplemental consolidated financial statements as of December 31, 1999 and 1998 and for each of the years in the three year period ended December 31, 1999, which have been restated to include the effects of the Lake Ariel Bancorp, Inc. merger, which was accounted for as a pooling of interests. We will provide to each person, including any beneficial owner, to whom a prospectus is delivered, a copy of any or all of the information that has been incorporated by reference in the prospectus but not delivered with the prospectus. We will provide this information upon written or oral request at no cost to the requester. You may obtain documents incorporated by reference in this prospectus by requesting them in writing or by telephone from us at the following address: NBT Bancorp Inc. 52 South Broad Street Norwich, New York 13815 Attention: Michael J. Chewens, CPA Tel: (607) 337-6520 YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED OR INCORPORATED BY REFERENCE IN THIS PROSPECTUS IN MAKING YOUR DECISION TO INVEST IN OUR COMPANY AND STOCK. WE HAVE NOT AUTHORIZED ANYONE TO PROVIDE YOU WITH INFORMATION THAT IS DIFFERENT FROM WHAT IS CONTAINED IN THIS PROSPECTUS. YOU SHOULD NOT ASSUME THAT THE INFORMATION CONTAINED IN THIS PROSPECTUS IS ACCURATE AS OF ANY DATE OTHER THAN SUCH DATE, AND THE USE OF THIS PROSPECTUS SHALL NOT CREATE ANY IMPLICATION TO THE CONTRARY. NBT BANCORP INC. We are a registered bank holding company incorporated in the State of Delaware and the parent holding company of NBT Bank, N.A. and LA Bank, N.A., each a national bank. NBT Bank is a full service commercial bank providing a broad range of financial products and services in central and northern New York. On February 17, 2000, 3

we completed our acquisition of Lake Ariel Bancorp, Inc., the parent holding company of LA Bank. Upon completion of the merger, LA Bank became our wholly-owned subsidiary. LA Bank provides commercial banking products and services in northeastern Pennsylvania. The following financial information reflects our merger with Lake Ariel on a pooled basis. In fiscal year ended December 31, 1999, our net income was $22.2 million. As of December 31, 1999, our total assets were approximately $2.0 billion, total deposits were approximately $1.5 billion and stockholders' equity was approximately $159.9 million. On December 7, 1999, we entered into an agreement with Pioneer American Holding Company Corp., a registered bank holding company incorporated in the Commonwealth of Pennsylvania. Pioneer American is the parent holding company of Pioneer American Bank, National Association, a national bank. Pioneer American Bank provides commercial banking products and services in northeastern Pennsylvania. In fiscal year 1999, Pioneer American's net income was $4.1 million. As of December 31, 1999, Pioneer American's total assets were approximately $418.8 million, total deposits were approximately $299.5 million and stockholders' equity was approximately $31.6 million. The stockholders of NBT and Pioneer American will vote upon the merger at their respective stockholders' meetings on June 20, 2000. We will account for the acquisition of Pioneer American as a pooling of interests. On April 20, 2000, we and BSB Bancorp, Inc., a Delaware corporation, announced that we would merge. Following our merger with BSB, we will be the surviving corporation. We and BSB will choose a new name for the surviving corporation before our merger with BSB occurs. The surviving corporation will have assets of approximately $4.7 billion. The surviving corporation will have three direct operating subsidiaries including two community banks (the combined NBT and BSB banks and the combined Lake Ariel and Pioneer American banks) and a financial services company, NBT Financial Services, Inc. Stockholders of BSB will receive two shares of our common stock for each share exchanged. We will issue approximately 20.5 million shares of our common stock to the former stockholders of BSB upon completion of the merger. Based on the April 19, 2000, closing price of our common stock on the Nasdaq National Market, the transaction was valued at $251 million or $24.00 per share for the outstanding common stock of BSB. The merger with BSB, which our board of directors and that of BSB have unanimously approved, is subject to approval by each company's stockholders and by banking regulators. We anticipate the merger will close in the fourth quarter of 2000. We intend the merger with BSB to be accounted for as a pooling-of-interests and to qualify as a tax-free exchange for BSB stockholders. Simultaneous with our merger with BSB, our and BSB's principal banking subsidiaries, NBT Bank and BSB Bank & Trust Company, will merge, with NBT Bank being the surviving bank in the bank merger. The surviving bank will be one of the largest independent community banks in upstate New York. The surviving bank will serve 12 counties from more than 55 offices and over 100 ATMs. A new name will be chosen for the surviving bank prior to our merger with BSB. The surviving corporation will have a 15-seat board of directors which will be made up of seven directors designated by BSB from the members of its board of directors and six directors designated by us from the members of our board, plus one designated by us from the former Lake Ariel Bancorp, Inc., which we acquired in February 2000, and who is serving on our Board and one designated by us from Pioneer American who is serving on our Board, subject to the closing of our merger with Pioneer American. If we do not complete our merger with Pioneer American before the effective time of the merger with BSB, the board of directors of the surviving corporation will consist of 13 directors, six of whom will be designated by BSB, six by us, and one former Lake Ariel board member who is serving on our Board. This former Lake Ariel board member will be designated by us. Upon completion of our merger with BSB, our common stockholders will have ownership of approximately 53 percent of the surviving corporation while BSB's common stockholders will own approximately 47 percent, assuming consummation of our merger with Pioneer American. Daryl R. Forsythe, our president and chief executive officer, will become the chairman, president and chief executive officer of the surviving corporation and William C. Craine, chairman of BSB, will become the vice chairman of the surviving corporation and chairman of its executive committee. Our Bank's president and chief operating officer, Martin A. Dietrich, will become the president and chief operating officer of the surviving bank. Michael J. 4

Chewens, our executive vice president and chief financial officer, will serve as chief financial officer for the surviving corporation. Other members of the executive management teams at NBT and BSB will retain key roles including: Glenn R. Small and John R. Bradley, executive vice presidents of lending and Larry Denniston, senior vice president and corporate secretary. The corporate offices of the surviving corporation will be located in Binghamton, New York. Other major bank functions will be conducted from the surviving corporation's Norwich, Binghamton and Scranton locations following the merger with BSB. The address of our principal executive offices is 52 South Broad Street, Norwich, New York 13815, and our telephone number is (607) 337-2265. USE OF PROCEEDS We will not receive any of the proceeds from the sale of the shares by Mr. Griffith. We will pay all expenses incurred in connection with the registration of the shares. Mr. Griffith will receive all net proceeds from the sale of the common stock under this prospectus. Mr. Griffith will pay all transaction costs associated with effecting any sales of the shares that occur. PRICE RANGE OF COMMON STOCK AND DIVIDENDS Our common stock trades on the Nasdaq National Market under the symbol "NBTB." The following table sets forth for the periods indicated (1) the range of high and low sales prices of our common stock and (2) the amount of cash dividends per share declared by us. SALES PRICES ------------ HIGH LOW DIVIDENDS ---- --- --------- 1998 First Quarter $19.05 $15.99 $ 0.117 Second Quarter 23.48 18.37 0.154 Third Quarter 23.81 17.58 0.154 Fourth Quarter 24.29 19.72 0.162 1999 First Quarter $23.33 $19.89 $ 0.162 Second Quarter 21.19 19.05 0.162 Third Quarter 20.90 16.43 0.162 Fourth Quarter 17.98 14.63 0.170 2000 First Quarter $16.50 $11.38 $0.170 Second Quarter 14.50 9.38 0.170 The timing and amount of future dividends we declare and pay will depend upon our earnings, cash requirements, and financial condition and those of our subsidiaries and, following our merger with BSB, the earnings, cash requirements, and financial condition of the surviving corporation, applicable government regulations, and other factors deemed relevant by the board of directors of the surviving corporation. Various federal and state laws limit the ability of affiliated banks to pay dividends to us. As of May 31, 2000, we had 4,814 holders of record of our common stock. 5

SELLING STOCKHOLDER The selling stockholder, David T. Griffith, offers for resale by means of this prospectus some or all of the shares that he acquired from us in May 2000 upon our acquisition of M. Griffith, Inc., a New York corporation. As a result of the acquisition, M. Griffith, Inc. became a wholly-owned subsidiary of NBT Financial Services, Inc., our wholly-owned subsidiary. Mr. Griffith was the sole stockholder of M. Griffith, Inc. In exchange for his shares of M. Griffith, Inc., we issued to Mr. Griffith and Hoover and Company as escrow agent a total of 420,989 shares of our common stock, which we refer to in this and the next section as the "subject shares." The subject shares constitute approximately 2.3% of our issued and outstanding shares as of the date of this prospectus. We have deposited a portion of the subject shares into an escrow account for the benefit of us and Mr. Griffith with Herkimer County Trust Company, Herkimer, New York, subject to an escrow agreement among us, NBT Financial Services, Inc., Mr. Griffith and Herkimer County Trust Company, dated as of May 5, 2000. In accordance with the terms of the escrow agreement, the escrow agent may release from escrow a portion of the escrowed shares to Mr. Griffith over the term of the escrow agreement only upon fulfillment of certain express employment conditions by Mr. Griffith. If and when such escrowed shares are released to Mr. Griffith from escrow, Mr. Griffith may sell any or all of such former escrowed shares. We will maintain the registered status of the escrowed shares with the SEC, thereby permitting Mr. Griffith to sell any of the subject shares upon their release from escrow. We will receive no portion of any proceeds from any sale of any of the subject shares by Mr. Griffith. Prior to our acquisition of M. Griffith, Inc., Mr. Griffith had no relationship or affiliation with us or any of our affiliates. Following the acquisition, Mr. Griffith entered into a three-year employment agreement with us as president of our subsidiary, M. Griffith, Inc. We are registering Mr. Griffith's shares to permit public secondary trading of the subject shares by Mr. Griffith and to allow Mr. Griffith to offer the subject shares for resale at such times as he chooses. We cannot give any estimate as to the number of shares that Mr. Griffith will hold after completion of this offering because he may offer some or all of the subject shares and because there currently are no agreements, arrangements or understandings with respect to the sale of any of the subject shares. Mr. Griffith may offer from time to time the subject shares held directly by him and those currently held in escrow but released from escrow to Mr. Griffith in the future. PLAN OF DISTRIBUTION We are registering all of the 420,989 subject shares of our common stock on behalf of Mr. Griffith. We issued the subject shares to Mr. Griffith and to the escrow agent in connection with our acquisition of M. Griffith, Inc. under an exemption from the registration requirements of the Securities Act of 1933, provided by Section 4(2) of that statute. We are registering the shares in accordance with the provisions of our acquisition agreement with M. Griffith, Inc. Depending on market conditions and other factors, Mr. Griffith may sell some or all of the subject shares offered by this prospectus from time to time, in one or more transactions, on the Nasdaq National Market, or otherwise, at market prices prevailing at the time of sale, at negotiated prices, or at fixed prices, which may be changed. Mr. Griffith may effect such sales directly, or through agents, or through dealers. Mr. Griffith may sell some or all of the subject shares in ordinary broker's transactions or through privately negotiated transactions or through a combination of any of these methods of sale. In connection with his sales, Mr. Griffith may pay usual and customary or specifically negotiated brokerage fees or commissions. Mr. Griffith will act independently from us in making decisions with respect to the timing, manner and size of each sale. The aggregate proceeds to Mr. Griffith from the sale of the subject shares will be the purchase price of the common stock sold less the aggregate agents' commissions, if any, and other expenses of issuance and distribution not borne by us. Mr. Griffith and any dealers or agents that participate in the distribution of the subject shares may be deemed to be "underwriters" within the meaning of the Securities Act of 1933. Any profit on the sale of the shares and any commissions received by any such dealer or agent in effecting sales of Mr. Griffith's shares may be deemed to be underwriting discounts and commissions under the Securities Act. There is no underwriter or coordinating broker acting in connection with the proposed sale of the subject shares by Mr. Griffith. 6

Mr. Griffith will sell the subject shares only through registered or licensed brokers or dealers if required under applicable state securities laws. Because Mr. Griffith may be deemed to be an underwriter within the meaning of Section 2(11) under the Securities Act, he will be subject to the prospectus delivery requirements of the Securities Act. We will make copies of this prospectus available to Mr. Griffith and have informed him of the need for delivery of copies of this prospectus to purchasers at or prior to the time of any sale of the subject shares. We will bear all costs and expenses, including registration and accounting fees and the fees, disbursements and expenses of our counsel, in connection with the registration of the subject shares under the Securities Act. Mr. Griffith will bear all commissions and discounts, if any, payable with respect to sales of the subject shares. Mr. Griffith will pay any transaction costs associated with effecting any sales that occur. Mr. Griffith may agree to indemnify any broker-dealer or agent that participates in transactions involving sales of the subject shares against certain liabilities, including liabilities arising under the Securities Act. DESCRIPTION OF NBT CAPITAL STOCK AUTHORIZED CAPITAL STOCK. Our current authorized stock consists of 30,000,000 shares of common stock, $.01 par value per share, and 2,500,000 shares of preferred stock, $.01 par value per share. No shares of the preferred stock are outstanding. Our Board is authorized to issue, without further stockholder approval, preferred stock from time to time in one or more series, and to determine the provisions applicable to each series, including the number of shares, dividend rights, dividend rate, conversion rights, voting rights, rights and terms of redemption, sinking fund provisions, redemption price or prices, and liquidation preferences. As of May 31, 2000, 18,522,291 shares of our common stock were outstanding. Additionally, upon completion of our mergers with Pioneer American and BSB, we anticipate issuing approximately 5.2 million shares and 20.5 million shares, respectively, to the former stockholders of those corporations. Prior to completion of our merger with BSB, we will request our stockholders to amend our Certificate of Incorporation to increase the number of our authorized shares of common stock so that we will have a sufficient number of authorized shares to issue in our merger with BSB. COMMON STOCK. Under Delaware law, stockholders generally are not personally liable for a corporation's acts or debts. Subject to the preferential rights of any other shares or series of capital stock, holders of shares of our common stock are entitled to receive dividends on shares of common stock if, as and when authorized and declared by our Board out of funds legally available for dividends and to share ratably in our assets legally available for distribution to our stockholders in the event of our liquidation, dissolution or winding-up after payment of, or adequate provision for, all of our known debts and liabilities. Each outstanding share of our common stock entitles the holder to one vote on all matters submitted to a vote of stockholders, including the election of directors. Unless a larger vote is required by law, our certificate of incorporation or our bylaws, when a quorum is present at a meeting of stockholders, a majority of the votes properly cast upon any question other than the election of directors shall decide the question. A plurality of the votes properly cast for the election of a person to serve as a director shall elect such person. Except as otherwise required by law or except as provided with respect to any other class or series of capital stock, the holders of our common stock possess the exclusive voting power. There is no cumulative voting in the election of directors. Our Board is classified into three categories with each category equal in number. This means, in general, that one-third of the members of our Board are subject to reelection at each annual meeting of stockholders. Holders of our common stock have no conversion, sinking fund or redemption rights, or preemptive rights to subscribe for any of our classes of stock. All shares of our common stock have equal dividend, distribution, liquidation and other rights, and have no preference, appraisal or exchange rights. PREFERRED STOCK. Our Board is authorized, without any further vote or action by our stockholders, to issue shares of preferred stock in one or more series, to establish the number of shares in each series and to fix the designation, 7

powers, preferences and rights of each such series and the qualifications, limitations or restrictions of the series, in each case, if any, as are permitted by Delaware law. Because our Board has the power to establish the preferences and rights of each class or series of preferred stock, it may afford the stockholders of any series or class of preferred stock preferences, powers and rights, voting or otherwise, senior to the rights of holders of shares of our common stock. The issuance of shares of preferred stock could have the effect of delaying, deferring or preventing a change in control of our corporation. STOCKHOLDER RIGHTS PLAN. In November 1994, we adopted a stockholder rights plan designed to ensure that any potential acquiror of our corporation would negotiate with our Board and that all of our stockholders would be treated equitably in the event of a takeover attempt. At that time, we paid a dividend of one Preferred Share Purchase Right for each outstanding share of our common stock. Similar rights are attached to each share of our common stock issued after November 15, 1994. Under the rights plan, the rights will not be exercisable until a person or group acquires beneficial ownership of 20 percent or more of our outstanding common stock, begins a tender or exchange offer for 25 percent or more of our common stock, or an adverse person, as declared by our Board, acquires 10 percent or more of our common stock. Additionally, until the occurrence of such an event, the rights are not severable from our common stock and therefore, the rights will transfer upon the transfer of shares of our common stock. Upon the occurrence of such events, each right entitles the holder to purchase one one-hundredth of a share of our Series R Preferred Stock, $.01 par value per share, at a price of $100. The rights plan also provides that upon the occurrence of certain specified events the holders of rights will be entitled to acquire additional equity interests in us or in the acquiring entity, such interests having a market value of two times the right's exercise price of $100. The rights expire November 14, 2004, and are redeemable in whole, but not in part, at our option prior to the time they become exercisable, for a price of $.01 per right. The rights have certain anti-takeover effects. The rights may cause substantial dilution to a person or group that attempts to acquire us on terms not approved by our Board. The rights should not interfere with any merger or other business combination approved by our Board. REGISTRAR AND TRANSFER AGENT. Our registrar and transfer agent is American Stock Transfer and Trust Company, New York, New York. LEGAL MATTERS The validity of the shares of our common stock offered hereby has been passed upon by Duane, Morris & Heckscher LLP, Washington, D.C. EXPERTS The consolidated financial statements and the supplemental consolidated financial statements of NBT as of December 31, 1999 and 1998 and for each of the years in the three-year period ended December 31, 1999 have been incorporated by reference in this prospectus and registration statement in reliance upon the reports of KPMG LLP, independent certified public accountants, which are incorporated herein by reference, and upon the authority of said firm as experts in accounting and auditing. The consolidated financial statements of Pioneer American as of December 31, 1999 and 1998 and for each of the years in the three-year period ended December 31, 1999, have been incorporated by reference in this prospectus and registration statement in reliance upon the report of KPMG LLP, independent certified public accountants, which is incorporated herein by reference, and upon the authority of said firm as experts in accounting and auditing. The consolidated financial statements of BSB Bancorp, Inc. as of December 31, 1999 and 1998 and for each of the years in the three-year period ended December 31, 1999 have been incorporated by reference in this prospectus and registration statement in reliance upon the report of PricewaterhouseCoopers LLP, independent certified public accountants, given on the authority of said firm as experts in accounting and auditing. 8

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS We have used and incorporated by reference "forward-looking statements" in this prospectus. Words such as "will," "will permit," "will afford," "believes," "expects," "may," "should," "projected," "contemplates," or "anticipates" may constitute forward-looking statements. These statements are within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934 and are subject to risks and uncertainties that could cause our actual results to differ materially. We have used these statements to describe our expectations and estimates in various sections of this prospectus, including: o NBT Bancorp Inc.; o Selling Stockholder; o Plan of Distribution; and o Description of NBT Capital Stock. Factors that might cause such differences include, but are not limited to: the timing of closing of our proposed mergers being delayed; competitive pressures among financial institutions increasing significantly; economic conditions, either nationally or locally in areas in which we and our prospective merger partners conduct our respective operations, being less favorable than expected; the cost and effort required to integrate aspects of the operations of the companies we will acquire being more difficult than we expected; our expected cost savings from our proposed mergers not being fully realized or realized within the expected time frame; legislation or regulatory changes which adversely affect the ability of our company following our proposed acquisitions to conduct its current and future operations; and the impact of the transition to the year 2000 on the operations of us or our merger partners. We disclaim any obligation to update any such factors or to publicly announce the result of any revisions to any of the forward-looking statements included in this prospectus to reflect future events or developments. Our actual results could differ materially from those set forth in the forward-looking statements because of many reasons, including the risk factors we list above. This list may not be exhaustive. 9

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS The following unaudited pro forma condensed combined balance sheet presents the financial position of NBT Bancorp Inc. (NBT), BSB Bancorp, Inc. (BSB), and Pioneer American Holding Company Corp. (Pioneer American) as of March 31, 2000 assuming that both mergers had occurred as of March 31, 2000 after giving effect to certain pro forma adjustments described in the accompanying notes. The following unaudited pro forma condensed combined statements of income for the three months ended March 31, 2000 and 1999, and the years ended December 31, 1999, 1998, and 1997 present the combined historical results of operations of NBT, BSB, and Pioneer American as if the mergers had been completed as of the first day of the period presented. The historical financial information of NBT has been restated to include the effects of the merger with Lake Ariel Bancop, Inc. (Lake Ariel), which was completed on February 17, 2000 and has been accounted for as a pooling of interests. Pro forma earnings per share are based on the exchange ratios of 2.0 and 1.805 for the BSB and Pioneer American mergers, respectively. The fiscal years of NBT, BSB, and Pioneer American end December 31. The unaudited pro forma condensed combined balance sheet reflects estimated non-recurring charges that may be incurred in connection with the mergers. The unaudited pro forma condensed combined financial statements were prepared giving effect to the mergers on the pooling of interests accounting method. Under this method of accounting, the recorded assets, liabilities, stockholders' equity, income and expense of NBT, BSB, and Pioneer American are combined and reflected at their historical amounts, except as noted in the accompanying notes. The combined company expects to achieve certain merger benefits in the form of operating expense reductions and revenue enhancements. The unaudited pro forma condensed combined statements of income do not reflect potential operating expense reductions or revenue enhancements that are expected to result from the mergers, and therefore may not be indicative of the results of future operations. No assurance can be given with respect to the ultimate level of operating expense reductions or revenue enhancements. The unaudited pro forma condensed combined financial statements should be read in conjunction with, and are qualified in their entirety by, the historical consolidated financial statements and accompanying notes of NBT, BSB, and Pioneer American and the supplemental consolidated financial statements and accompanying notes of NBT, which have been restated to include the effects of the Lake Ariel merger. These supplemental financial statements were included in Current Report on Form 8-K, dated March 31, 2000 and incorporated by reference herein. The following historical financial information of Pioneer American and BSB has been derived from the respective companies' interim consolidated financial statements as of March 31, 2000 and for the three months ended March 31, 2000 and 1999 which are included in the respective companies Form 10-Q for the three months ended March 31, 2000 and filed with the SEC, and their respective consolidated financial statements and accompanying notes as of December 31, 1999 and 1998 and for each of the years in the three year period ended December 31, 1999, which were included in the respective companies' Form 10-K for the year ended December 31, 1999. The consolidated financial statements of BSB and Pioneer American as of December 31, 1999 and 1998 and for each of the years in the three year period ended December 31, 1999 are incorporated by reference into this registration statement. The unaudited pro forma condensed combined financial statements are presented for informational purposes only. These statements are not necessarily indicative of the combined financial position and results of operations that would have occurred if the mergers had been completed on March 31, 2000 or at the beginning of the respective periods presented or that may be attained in the future. 10

Unaudited Pro Forma Condensed Combined Balance Sheet March 31, 2000 (in thousands) NBT BSB Pioneer American NBT BSB Pro Forma Combined Holding Pro Forma Combined Bancorp Inc. Bancorp, Inc. Adjustments Pro Forma Company Corp. Adjustments Pro Forma ------------ ------------- ----------- --------- ---------------- ----------- --------- ASSETS Cash and cash equivalents $ 60,823 $ 47,718 $ -- $ 108,541 $ 13,216 $ -- $ 121,757 Securities available for sale, at fair value 497,528 382,703 -- 880,231 105,239 -- 985,470 Securities held to maturity (fair value-NBT Bancorp Inc. $75,808, BSB Bancorp, Inc. $13,208, and Pioneer American Holding Company Corp. $34,560) 78,772 13,079 -- 91,851 35,746 -- 127,597 Loans 1,295,651 1,745,959 3,041,610 245,147 3,286,757 Less: Allowance for loan losses 17,543 31,705 -- 49,248 3,145 -- 52,393 - ----------------------------------------------------------------------------------------------------------------------------------- Net loans 1,278,108 1,714,254 -- 2,992,362 242,002 -- 3,234,364 Premises and equipment, net 40,292 15,541 -- 55,833 5,910 -- 61,743 Other assets 73,583 57,569 4,500 135,652 13,615 1,300 150,567 - ----------------------------------------------------------------------------------------------------------------------------------- TOTAL ASSETS $ 2,029,106 $ 2,230,864 $ 4,500 $4,264,470 $ 415,728 $ 1,300 $4,681,498 =================================================================================================================================== LIABILITIES AND STOCKHOLDERS' EQUITY Deposits: Demand (noninterest bearing) $ 210,579 $ 139,639 $ -- $ 350,218 $ 45,842 $ -- 396,060 Savings,NOW, and money market 490,328 653,091 -- 1,143,419 110,880 -- 1,254,299 Time 822,842 1,106,548 -- 1,929,390 143,152 -- 2,072,542 - ----------------------------------------------------------------------------------------------------------------------------------- Total deposits 1,523,749 1,899,278 -- 3,423,027 299,874 -- 3,722,901 Borrowings 327,238 135,982 -- 463,220 79,489 -- 542,709 Other liabilities 15,587 8,588 16,500 40,675 4,272 5,100 50,047 Mandatorily redeemable preferred securities of subsidiary -- 30,000 -- 30,000 -- -- 30,000 - ----------------------------------------------------------------------------------------------------------------------------------- Total liabilities 1,866,574 2,073,848 16,500 3,956,922 383,635 5,100 4,345,657 - ----------------------------------------------------------------------------------------------------------------------------------- Stockholders' equity: Preferred stock -- -- -- -- -- -- -- Common stock 186 114 91 391 2,935 (2,883) 443 Additional paid-in-capital 167,047 37,590 (13,548) 191,089 11,962 1,153 204,204 Retained earnings 24,225 143,481 (12,000) 155,706 22,355 (3,800) 174,261 Accumulated other comprehensive income (loss) (17,615) (10,712) -- (28,327) (3,429) -- (31,756) Common stock in treasury, at cost (11,311) (13,457) 13,457 (11,311) (1,730) 1,730 (11,311) - ----------------------------------------------------------------------------------------------------------------------------------- Total stockholders' equity 162,532 157,016 (12,000) 307,548 32,093 (3,800) 335,841 - ----------------------------------------------------------------------------------------------------------------------------------- TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY $ 2,029,106 $ 2,230,864 $ 4,500 $4,264,470 $ 415,728 $ 1,300 $4,681,498 =================================================================================================================================== See accompanying notes to unaudited pro forma condensed combined financial statements 11

Unaudited Pro Forma Condensed Combined Statement of Income For the Three Months Ended March 31, 2000 Pioneer NBT NBT American BSB BSB Holding Pioneer NBT BSB Pro Forma Combined Company Pro Forma Combined Bancorp Inc. Bancorp, Inc. Adjustments Pro Forma Corp. Adjustments Pro Forma ------------ ------------- ----------- --------- ----------- ----------- ---------- Interest and fee income: Loan $ 27,189 $ 39,593 $ -- $ 66,782 $ 5,048 $ -- $ 71,830 Securities 9,865 6,674 -- 16,539 2,358 -- 18,897 Other 402 13 -- 415 4 -- 419 - -------------------------------------------------------------------------------------------------------------------------------- Total interest and fee income: 37,456 46,280 -- 83,736 7,410 -- 91,146 - -------------------------------------------------------------------------------------------------------------------------------- Interest expense: Deposits 13,446 21,319 -- 34,765 2,637 -- 37,402 Borrowings 4,400 2,582 -- 6,982 1,135 -- 8,117 - -------------------------------------------------------------------------------------------------------------------------------- Total interest expense 17,846 23,901 -- 41,747 3,772 -- 45,519 - -------------------------------------------------------------------------------------------------------------------------------- Net interest income 19,610 22,379 -- 41,989 3,638 -- 45,627 Provision for loan losses 1,334 4,608 -- 5,942 120 -- 6,062 - -------------------------------------------------------------------------------------------------------------------------------- Net interest income after provision for loan losses 18,276 17,771 -- 36,047 3,518 -- 39,565 - -------------------------------------------------------------------------------------------------------------------------------- Noninterest income: Trust 860 331 -- 1,191 -- -- 1,191 Service charges on deposit accounts 1,620 1,213 -- 2,833 526 -- 3,359 Net security gains (losses) - - -- -- -- -- -- Other 1,135 1,817 -- 2,952 195 -- 3,147 - -------------------------------------------------------------------------------------------------------------------------------- Total noninterest income 3,615 3,361 -- 6,976 721 -- 7,697 - -------------------------------------------------------------------------------------------------------------------------------- Noninterest expense: Salaries and employee benefits 7,081 5,899 -- 12,980 1,322 -- 14,302 Office supplies and postage 592 393 -- 985 119 -- 1,104 Occupancy 1,232 727 -- 1,959 269 -- 2,228 Equipment 1,137 442 -- 1,579 225 -- 1,804 Professional fees and outside services 756 1,479 -- 2,235 240 -- 2,475 Data processing and communications 1,132 416 -- 1,548 96 -- 1,644 Amortization of intangible assets 312 96 -- 408 10 -- 418 Merger and acquisition charges 1,122 -- -- 1,122 -- -- 1,122 Other operating 1,619 2,261 -- 3,880 494 -- 4,374 - -------------------------------------------------------------------------------------------------------------------------------- Total noninterest expense 14,983 11,713 -- 26,696 2,775 -- 29,471 - -------------------------------------------------------------------------------------------------------------------------------- Income before income taxes 6,908 9,419 -- 16,327 1,464 -- 17,791 Income taxes 2,667 3,671 -- 6,338 425 -- 6,763 - -------------------------------------------------------------------------------------------------------------------------------- - -------------------------------------------------------------------------------------------------------------------------------- Net Income $ 4,241 $ 5,748 $ -- $ 9,989 $ 1,039 $ -- $ 11,028 ================================================================================================================================ Weighted Average Shares Outstanding Basic 18,028 10,243 38,514 2,864 43,684 Diluted 18,134 10,337 38,808 2,887 44,019 Earnings Per Share Basic 0.24 0.56 0.26 0.36 0.25 Diluted 0.23 0.56 0.26 0.36 0.25 See accompanying notes to unaudited pro forma condensed combined financial statements 12

Unaudited Pro Forma Condensed Combined Statement of Income For the Three Months Ended March 31, 1999 Pioneer NBT NBT American BSB BSB Holding Pioneer NBT BSB Pro Forma Combined Company Pro Forma Combined Bancorp Inc. Bancorp, Inc. Adjustments Pro Forma Corp. Adjustments Pro Forma ------------ -------------- ------------ ---------- --------- ------------ ---------- Interest and fee income: Loan $ 22,679 $ 35,463 $ -- $ 58,142 $ 4,812 $ -- $ 62,954 Securities 8,465 6,838 -- 15,303 2,291 -- 17,594 Other 458 204 -- 662 82 -- 744 - ---------------------------------------------------------------------------------------------------------------------------------- Total interest and fee income: 31,602 42,505 -- 74,107 7,185 -- 81,292 - ---------------------------------------------------------------------------------------------------------------------------------- Interest expense: Deposits 11,006 17,927 -- 28,933 2,729 -- 31,662 Borrowings 2,878 3,466 -- 6,344 968 -- 7,312 - ---------------------------------------------------------------------------------------------------------------------------------- Total interest expense 13,884 21,393 -- 35,277 3,697 -- 38,974 - ---------------------------------------------------------------------------------------------------------------------------------- Net interest income 17,718 21,112 -- 38,830 3,488 -- 42,318 Provision for loan losses 1,120 3,461 -- 4,581 75 -- 4,656 - ---------------------------------------------------------------------------------------------------------------------------------- Net interest income after provision for loan losses 16,598 17,651 -- 34,249 3,413 -- 37,662 - ---------------------------------------------------------------------------------------------------------------------------------- Noninterest income: Trust 835 251 -- 1,086 -- -- 1,086 Service charges on deposit accounts 1,408 1,000 -- 2,408 517 -- 2,925 Net security gains (losses) 668 (401) -- 267 -- -- 267 Other 1,365 1,539 -- 2,904 126 -- 3,030 - ---------------------------------------------------------------------------------------------------------------------------------- Total noninterest income 4,276 2,389 -- 6,665 643 -- 7,308 - ---------------------------------------------------------------------------------------------------------------------------------- Noninterest expense: Salaries and employee benefits 5,970 5,081 -- 11,051 1,331 -- 12,382 Office supplies and postage 637 433 -- 1,070 145 -- 1,215 Occupancy 1,024 773 -- 1,797 285 -- 2,082 Equipment 947 427 -- 1,374 242 -- 1,616 Professional fees and outside services 697 1,331 -- 2,028 183 -- 2,211 Data processing and communications 972 490 -- 1,462 118 -- 1,580 Amortization of intangible assets 329 96 -- 425 10 -- 435 Other operating 1,240 2,533 -- 3,773 559 -- 4,332 - ---------------------------------------------------------------------------------------------------------------------------------- Total noninterest expense 11,816 11,164 -- 22,980 2,873 -- 25,853 - ---------------------------------------------------------------------------------------------------------------------------------- Income before income taxes 9,058 8,876 -- 17,934 1,183 -- 19,117 Income taxes 3,282 3,340 -- 6,622 300 -- 6,922 - ---------------------------------------------------------------------------------------------------------------------------------- - ---------------------------------------------------------------------------------------------------------------------------------- Net Income $ 5,776 $ 5,536 $ -- $ 11,312 $ 883 $ -- $ 12,195 ================================================================================================================================== Weighted Average Shares Outstanding Basic 17,860 10,071 38,002 2,921 43,274 Diluted 18,104 10,341 38,786 2,947 44,105 Earnings Per Share Basic 0.32 0.55 0.30 0.30 0.28 Diluted 0.32 0.54 0.29 0.30 0.28 See accompanying notes to unaudited pro forma condensed combined financial statements 13

Unaudited Pro Forma Condensed Combined Statement of Income For the Year Ended December 31, 1999 Pioneer NBT NBT American BSB BSB Holding Pioneer NBT BSB Pro Forma Combined Company Pro Forma Combined Bancorp Inc. Bancorp, Inc. Adjustments Pro Forma Corp. Adjustments Pro Forma ------------ ------------- ----------- --------- ---------- ------------ ----------- Interest and fee income: Loans $ 96,235 $ 151,001 $ -- $ 247,236 $ 19,661 $ -- $ 266,897 Securities 38,166 25,038 -- 63,204 9,491 -- 72,695 Other 988 682 -- 1,670 237 -- 1,907 - -------------------------------------------------------------------------------------------------------------------------------- Total interest and fee income: 135,389 176,721 -- 312,110 29,389 -- 341,499 - -------------------------------------------------------------------------------------------------------------------------------- Interest expense: Deposits 46,067 75,542 -- 121,609 10,519 -- 132,128 Borrowings 14,515 14,034 -- 28,549 4,379 -- 32,928 - -------------------------------------------------------------------------------------------------------------------------------- Total interest expense 60,582 89,576 -- 150,158 14,898 -- 165,056 - -------------------------------------------------------------------------------------------------------------------------------- Net interest income 74,807 87,145 -- 161,952 14,491 -- 176,443 Provision for loan losses 5,070 19,137 -- 24,207 370 -- 24,577 - -------------------------------------------------------------------------------------------------------------------------------- Net interest income after provision for loan losses 69,737 68,008 -- 137,745 14,121 -- 151,866 - -------------------------------------------------------------------------------------------------------------------------------- Noninterest income: Trust 3,305 1,104 -- 4,409 -- -- 4,409 Service charges on deposit accounts 6,303 4,382 -- 10,685 1,635 -- 12,320 Net security gains (losses) 1,716 (231) -- 1,485 88 -- 1,573 Other 5,097 7,116 -- 12,213 1,108 -- 13,321 - -------------------------------------------------------------------------------------------------------------------------------- Total noninterest income 16,421 12,371 -- 28,792 2,831 -- 31,623 - -------------------------------------------------------------------------------------------------------------------------------- Noninterest expense: Salaries and employee benefits 25,213 20,386 -- 45,599 5,291 -- 50,890 Office supplies and postage 2,436 1,684 -- 4,120 534 -- 4,654 Occupancy 4,317 2,874 -- 7,191 1,062 -- 8,253 Equipment 4,230 1,733 -- 5,963 990 -- 6,953 Professional fees and outside services 3,325 6,001 -- 9,326 1,005 -- 10,331 Data processing and communications 4,091 1,930 -- 6,021 437 -- 6,458 Amortization of intangible assets 1,278 386 -- 1,664 39 -- 1,703 Merger and acquisition charges 798 5,408 -- 6,206 -- -- 6,206 Other operating 5,812 10,261 -- 16,073 2,024 -- 18,097 - -------------------------------------------------------------------------------------------------------------------------------- Total noninterest expense 51,500 50,663 -- 102,163 11,382 -- 113,545 - -------------------------------------------------------------------------------------------------------------------------------- Income before income taxes 34,658 29,716 -- 64,374 5,570 -- 69,944 Income taxes 12,483 11,491 -- 23,974 1,488 -- 25,462 - -------------------------------------------------------------------------------------------------------------------------------- - -------------------------------------------------------------------------------------------------------------------------------- Net Income $ 22,175 $ 18,225 $ -- $ 40,400 $ 4,082 $ -- $ 44,482 ================================================================================================================================ Weighted Average Shares Outstanding Basic 17,851 10,138 38,127 2,902 43,365 Diluted 18,095 10,312 38,719 2,929 44,006 Earnings Per Share Basic 1.24 1.80 1.06 1.41 1.03 Diluted 1.23 1.77 1.04 1.39 1.01 See accompanying notes to unaudited pro forma condensed combined financial statements 14

Unaudited Pro Forma Condensed Combined Statement of Income For the Year Ended December 31, 1998 Pioneer NBT NBT American BSB BSB Holding Pioneer NBT BSB Pro Forma Combined Company Pro Forma Combined Bancorp Inc. Bancorp, Inc. Adjustments Pro Forma Corp. Adjustments Pro Forma ------------- ------------- ------------ ----------- ---------- ------------- ---------- Interest and fee income: Loans $ 89,399 $ 139,374 $ -- $ 228,773 $ 19,093 $ -- $ 247,866 Securities 40,370 25,926 -- 66,296 8,729 -- 75,025 Other 531 866 -- 1,397 480 -- 1,877 - ----------------------------------------------------------------------------------------------------------------------------------- Total interest and fee income: 130,300 166,166 -- 296,466 28,302 -- 324,768 - ----------------------------------------------------------------------------------------------------------------------------------- Interest expense: Deposits 48,058 72,387 -- 120,445 10,840 -- 131,285 Borrowings 12,359 12,399 -- 24,758 3,479 -- 28,237 - ----------------------------------------------------------------------------------------------------------------------------------- Total interest expense 60,417 84,786 -- 145,203 14,319 -- 159,522 - ----------------------------------------------------------------------------------------------------------------------------------- Net interest income 69,883 81,380 -- 151,263 13,983 -- 165,246 Provision for loan losses 5,729 12,931 -- 18,660 420 -- 19,080 - ---------------------------------------------------------------------------------------------------------------------------------- Net interest income after provision for loan losses 64,154 68,449 -- 132,603 13,563 -- 146,166 - ----------------------------------------------------------------------------------------------------------------------------------- Noninterest income: Trust 3,115 994 -- 4,109 -- -- 4,109 Service charges on deposit accounts 5,325 3,714 -- 9,039 1,404 -- 10,443 Net security gains (losses) 1,056 (851) -- 205 511 -- 716 Other 5,417 4,738 -- 10,155 1,046 -- 11,201 - ----------------------------------------------------------------------------------------------------------------------------------- Total noninterest income 14,913 8,595 -- 23,508 2,961 -- 26,469 - ----------------------------------------------------------------------------------------------------------------------------------- Noninterest expense: Salaries and employee benefits 24,215 19,528 -- 43,743 5,071 -- 48,814 Office supplies and postage 2,523 1,998 -- 4,521 506 -- 5,027 Occupancy 4,132 2,911 -- 7,043 1,027 -- 8,070 Equipment 3,599 1,466 -- 5,065 773 -- 5,838 Professional fees and outside services 3,375 4,086 -- 7,461 1,027 -- 8,488 Data processing and communications 3,796 2,027 -- 5,823 483 -- 6,306 Amortization of intangible assets 1,275 386 -- 1,661 39 -- 1,700 Other operating 7,665 9,581 -- 17,246 2,041 -- 19,287 - ----------------------------------------------------------------------------------------------------------------------------------- Total noninterest expense 50,580 41,983 -- 92,563 10,967 -- 103,530 - ----------------------------------------------------------------------------------------------------------------------------------- Income before income taxes 28,487 35,061 -- 63,548 5,557 -- 69,105 Income taxes 5,614 13,542 -- 19,156 1,535 -- 20,691 - ----------------------------------------------------------------------------------------------------------------------------------- - ----------------------------------------------------------------------------------------------------------------------------------- Net Income $ 22,873 $ 21,519 $ -- $ 44,392 $ 4,022 $ -- $ 48,414 =================================================================================================================================== Weighted Average Shares Outstanding Basic 17,976 10,006 37,988 2,894 43,212 Diluted 18,361 10,365 39,091 2,953 44,421 Earnings Per Share Basic 1.27 2.15 1.17 1.39 1.12 Diluted 1.25 2.08 1.14 1.36 1.09 See accompanying notes to unaudited pro forma condensed combined financial statements 15

Unaudited Pro Forma Condensed Combined Statement of Income For the Year Ended December 31, 1997 NBT NBT Pioneer BSB BSB American Pioneer NBT BSB Pro Forma Combined Holding Pro Forma Combined Bancorp Inc. Bancorp, Inc. Adjustments Pro Forma Company Corp. Adjustments Pro Forma ------------ ------------- ----------- ----------- ------------- ------------ ----------- Interest and fee income: Loans $ 81,688 $ 120,750 $ -- $ 202,438 $ 18,101 $ -- $ 220,539 Securities 38,536 20,398 -- 58,934 8,086 -- 67,020 Other 607 200 -- 807 320 -- 1,127 - ---------------------------------------------------------------------------------------------------------------------------------- Total interest and fee income: 120,831 141,348 -- 262,179 26,507 -- 288,686 - ---------------------------------------------------------------------------------------------------------------------------------- Interest expense: Deposits 45,629 60,180 -- 105,809 11,337 -- 117,146 Borrowings 10,418 11,272 -- 21,690 1,508 -- 23,198 - ---------------------------------------------------------------------------------------------------------------------------------- Total interest expense 56,047 71,452 -- 127,499 12,845 -- 140,344 - ---------------------------------------------------------------------------------------------------------------------------------- Net interest income 64,784 69,896 -- 134,680 13,662 -- 148,342 Provision for loan losses 4,285 10,814 -- 15,099 535 -- 15,634 - ---------------------------------------------------------------------------------------------------------------------------------- Net interest income after provision for loan losses 60,499 59,082 -- 119,581 13,127 -- 132,708 - ---------------------------------------------------------------------------------------------------------------------------------- Noninterest income: Trust 2,675 709 -- 3,384 -- -- 3,384 Service charges on deposit accounts 4,942 3,297 -- 8,239 1,397 -- 9,636 Net security gains (losses) (123) 380 -- 257 157 -- 414 Other 3,973 3,762 -- 7,735 907 -- 8,642 - ---------------------------------------------------------------------------------------------------------------------------------- Total noninterest income 11,467 8,148 -- 19,615 2,461 -- 22,076 - ---------------------------------------------------------------------------------------------------------------------------------- Noninterest expense: Salaries and employee benefits 22,111 17,121 -- 39,232 5,040 -- 44,272 Office supplies and postage 2,250 1,886 -- 4,136 507 -- 4,643 Occupancy 3,754 2,547 -- 6,301 1,026 -- 7,327 Equipment 2,632 1,378 -- 4,010 685 -- 4,695 Professional fees and outside services 2,485 2,716 -- 5,201 900 -- 6,101 Data processing and communications 2,966 1,358 -- 4,324 456 -- 4,780 Amortization of intangible assets 1,505 386 -- 1,891 39 -- 1,930 Other operating 6,677 9,548 -- 16,225 1,427 -- 17,652 - ---------------------------------------------------------------------------------------------------------------------------------- Total noninterest expense 44,380 36,940 -- 81,320 10,080 -- 91,400 - ---------------------------------------------------------------------------------------------------------------------------------- Income before income taxes 27,586 30,290 -- 57,876 5,508 -- 63,384 Income taxes 9,406 11,641 -- 21,047 1,500 -- 22,547 - ---------------------------------------------------------------------------------------------------------------------------------- - ---------------------------------------------------------------------------------------------------------------------------------- Net Income $ 18,180 $ 18,649 $ -- $ 36,829 $ 4,008 $ -- $ 40,837 ================================================================================================================================== Weighted Average Shares Outstanding Basic 17,095 9,905 36,905 2,850 42,049 Diluted 17,393 10,258 37,909 2,939 43,214 Earnings Per Share Basic 1.06 1.88 1.00 1.41 0.97 Diluted 1.05 1.82 0.97 1.36 0.94 See accompanying notes to unaudited pro forma condensed combined financial statements 16

NOTES TO UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS (1) Pro forma earnings per share have been calculated on the applicable weighted average number of shares of NBT plus the additional shares of NBT assumed to be issued in the mergers in exchange for the weighted average outstanding shares of BSB and Pioneer American for each applicable period based on the exchange ratios of 2.0 and 1.805, respectively. (2) Pro forma entry to retire treasury stock held by BSB (approximately 1,174,216 shares having a par value of $.01 per share): Common Stock ........................................................ 11,742 Paid in Capital ..................................................... 13,445,258 Treasury Stock .................................................. 13,457,000 BSB common stock issued at March 31, 2000 ........................... 11,430,761 Less treasury stock retired above ................................... (1,174,216) ---------- BSB common stock issued and outstanding at March 31, 2000........... 10,256,545 ========== Pro forma entry to issue 2.0 shares of NBT common stock in exchange for each share of BSB common stock: NBT common stock issued at March 31, 2000 .................................. 18,623,435 NBT common stock issued in exchange for BSB common stock after retirement of BSB's treasury stock (10,256,545 shares of BSB common stock times conversion ratio of 2.0).................................................... 20,513,090 ---------- Combined NBT/BSB pro forma total shares of common stock issued ............. 39,136,525 Par value per share of NBT common stock .................................... $.01 ----------- Combined NBT/BSB pro forma total par value ................................. $391,365 =========== Actual par value of common stock at March 31, 2000: NBT ........................................................................ $186,234 BSB (after retirement of treasury shares) .................................. 102,566 ----------- Total ...................................................................... $288,800 =========== Required increase in par value ............................................. $102,565 =========== Entry to conform par value of common stock: Paid in Capital....................................................... 102,565 Common stock...................................................... 102,565 17

Summary of pro forma entries above: Paid in Capital........................................................ 13,547,823 Common Stock....................................................... 90,823 Treasury Stock..................................................... 13,457,000 (3) Pro forma entry to retire treasury stock held by Pioneer American (approximately 71,060 shares having a par value of $1.00 per share): Common Stock....................................................... 71,060 Paid in Capital.................................................... 1,658,739 Treasury Stock................................................. 1,729,799 Pro forma entry to issue 1.805 shares of NBT common stock in exchange for each share of Pioneer American common stock. The par value of NBT common stock to be issued is determined as follows: Combined NBT/BSB pro forma common stock issued at March 31, 2000 (note 1)................................................................. 39,136,525 NBT common stock issued in exchange for Pioneer American common stock after retirement of Pioneer American treasury stock (2,864,307 shares of Pioneer American common stock times conversion ratio of 1.805).. 5,170,074 ----------- Combined pro forma total shares of common stock issued............. 44,306,599 Par value per share of common stock................................ $.01 ----------- Combined pro forma total par value................................. $ 443,066 =========== Actual par value of common stock at March 31, 2000: NBT/BSB combined pro forma (note 1)................................ $ 391,365 Pioneer American (after retirement of treasury shares)............. 2,864,307 --------- Total.............................................................. $ 3,255,672 ========== Required decrease in par value..................................... $ 2,812,606 ========== Entry to conform par value of common stock: Common stock....................................................... 2,812,606 Paid in Capital................................................. 2,812,606 Summary of pro forma entries above: Common Stock....................................................... 2,883,666 Paid in Capital................................................ 1,153,867 Treasury Stock................................................. 1,729,799 18

(4) Authorized, issued and outstanding share information is as follows at March 31, 2000: - ------------------------------------------------------------------------------------------------------------------------------------ NBT BSB NBT/BSB Pro forma Pioneer American NBT/BSB/ Pioneer American Pro forma - ------------------------------------------------------------------------------------------------------------------------------------ PREFERRED - ------------------------------------------------------------------------------------------------------------------------------------ Authorized 2,500,000 2,500,000 2,500,000 -- 5,000,000 - ------------------------------------------------------------------------------------------------------------------------------------ Issued and Outstanding -- -- -- -- -- - ------------------------------------------------------------------------------------------------------------------------------------ - ------------------------------------------------------------------------------------------------------------------------------------ COMMON - ------------------------------------------------------------------------------------------------------------------------------------ Par value $0.01 $0.01 $0.01 $1.00 $0.01 - ------------------------------------------------------------------------------------------------------------------------------------ Authorized 30,000,000 30,000,000 30,000,000 30,000,000 100,000,000 - ------------------------------------------------------------------------------------------------------------------------------------ Issued 18,623,435 11,430,761 39,136,525 2,935,367 44,306,599 - ------------------------------------------------------------------------------------------------------------------------------------ Outstanding 18,100,868 10,256,545 38,613,958 2,864,307 43,784,032 - ------------------------------------------------------------------------------------------------------------------------------------ - ------------------------------------------------------------------------------------------------------------------------------------ (5) The unaudited pro forma condensed combined balance sheet at March 31, 2000, reflects anticipated non-recurring merger and integration costs for both the Pioneer American and BSB mergers. Costs related to the Pioneer American merger are estimated to be in the range of $4.6 million to $5.6 million ($3.3 million to $4.3 million after taxes). Costs related to the BSB merger are estimated to be in the range of $16.0 million to $17.0 million ($11.5 million to $12.5 million after taxes). These estimates include primarily investment banking, legal, accounting, printing, data processing and system integration costs, and employee and contract termination costs. Anticipated merger and integration cost estimates are not included in the unaudited pro forma condensed combined statements of income for any of the periods presented. The pro forma statements do not reflect potential expense reductions or revenue enhancements expected to be realized subsequent to consummation of the mergers. The unaudited pro forma condensed combined balance sheet at March 31, 2000 only reflects merger and integration costs related to the Lake Ariel merger that were incurred through March 31, 2000. It is anticipated that there will be an additional $5.0 million of merger and integration costs incurred in the future in connection with the Lake Ariel merger. These additional costs are not recognized in the unaudited pro forma condensed combined balance sheet at March 31, 2000. The entries to record the anticipated merger and integration costs on the unaudited pro forma condensed combined balance sheet are as follows: BSB --- Current tax receivable............................................. 4,500,000 Retained earnings.................................................. 12,000,000 Other liabilities.............................................. 16,500,000 Pioneer American ---------------- Current tax receivable............................................. 1,300,000 Retained earnings.................................................. 3,800,000 Other liabilities.............................................. 5,100,000 19