NBT BANCORP INC
POS AM, 2000-05-10
NATIONAL COMMERCIAL BANKS
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      As filed with the Securities and Exchange Commission on May 10, 2000

                                           Registration Statement No. 333-30988

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

                                 ---------------
                         POST-EFFECTIVE AMENDMENT NO. 1
                                       TO

                                    FORM S-4

                             REGISTRATION STATEMENT

                        UNDER THE SECURITIES ACT OF 1933

                                 ---------------

                                NBT BANCORP INC.

             (Exact Name of Registrant as specified in its Charter)

                                 ---------------


    DELAWARE                          6712                       16-1268674

(State or Other          (Primary Standard Industrial         (I.R.S. Employer
Jurisdiction of           Classification Code Number)        Identification No.)
Incorporation or
Organization)


                              52 South Broad Street
                             Norwich, New York 13815
                                 (607) 337-2265
          (Address, Including Zip Code, and Telephone Number, Including
             Area Code of Registrant's Principal Executive Offices)

                                DARYL R. FORSYTHE
                      President and Chief Executive Officer
                                NBT Bancorp Inc.
                              52 South Broad Street
                             Norwich, New York 13815
                                 (607) 337-2265
                (Name, Address, Including Zip Code, and Telephone
               Number, Including Area Code, of Agent for Service)


<PAGE>


                                 ---------------
                                   Copies to:

   Brian D. Alprin, Esq.                      Lawrence R. Wiseman, Esq.
   Laurence S. Lese, Esq.                     Blank Rome Comisky & McCauley LLP
   Duane, Morris & Heckscher LLP              One Logan Square
   1667 K Street, NW, Suite 700               Philadelphia, PA 19103-6998
   Washington, DC 20006                       (215) 569-5500
   (202) 776-7800



================================================================================

<PAGE>



[NBT                                                          [PIONEER AMERICAN
LOGO APPEARS HERE]                                   LOGO APPEARS HERE]

                  SUPPLEMENTAL JOINT PROXY STATEMENT/PROSPECTUS

     On  April  5,   2000,   we  sent  to  our   stockholders   a  joint   proxy
statement/prospectus  describing, among other things, the proposed merger of our
two  companies.  We  indicated  that  the  boards  of  directors  of both of our
companies had  unanimously  agreed on the merger and that the board of directors
of  each  company  believed  the  merger  to be in  the  best  interests  of its
stockholders and unanimously  recommended that its stockholders  vote to approve
the merger agreement.  The boards of directors of each company as of the date of
this letter and the enclosed supplemental proxy statement/prospectus continue to
be of the same view and unanimously  support the merger. THIS SUPPLEMENTAL JOINT
PROXY STATEMENT/PROSPECTUS SUPPLEMENTS OUR APRIL 5, 2000 DOCUMENT.

     Since our April 5, 2000  letter and joint proxy  statement/prospectus,  NBT
Bancorp has entered into a merger  agreement with BSB Bancorp,  Inc., a Delaware
corporation  based in Binghamton,  New York. If NBT Bancorp completes its merger
with BSB Bancorp,  the combined company would have assets of approximately  $4.7
billion; the combined company would be about twice the size of NBT Bancorp, even
after  its  merger  with  Pioneer  American.   Because  of  the  importance  and
significance of this announcement,  we will not be able to vote on our merger at
our May 16,  2000  meetings.  This  supplement  will  discuss the  proposed  NBT
Bancorp-BSB  Bancorp merger and how it will impact the current  decision  before
NBT  Bancorp  and Pioneer  American  stockholders  relating to the merger of NBT
Bancorp and Pioneer American. Please read this supplement carefully. It contains
important  information  that you  should  know  before  you  decide to vote with
respect to the NBT  Bancorp/Pioneer  American  merger.  We are not asking you at
this time to vote on the NBT  Bancorp-BSB  Bancorp  merger.  IN THE  FUTURE  NBT
BANCORP AND BSB BANCORP  WILL PREPARE AND SEND A PROXY  STATEMENT/PROSPECTUS  TO
EACH OF THEIR  RESPECTIVE  STOCKHOLDERS  TO EXPLAIN  THAT  MERGER AND TO REQUEST
THEIR CONSIDERATION OF AND VOTE WITH RESPECT TO THAT MERGER.

     Each of us has  already  notified  our  stockholders  of our  intention  to
adjourn  our  respective  stockholders'  meetings  from May 16, 2000 to a future
date,  which we said was tentatively  June 20, 2000. We advise you that both the
NBT Bancorp stockholders' meeting and the Pioneer American stockholders' meeting
were adjourned to June 20, 2000. At its reconvened special meeting,  the Pioneer
American  stockholders  will consider and vote upon the merger agreement between
NBT Bancorp and Pioneer American and the merger of these companies.  NBT Bancorp
convened its annual  meeting as  scheduled  on May 16, 2000,  and voted upon the
election of  directors,  ratification  of the NBT Bancorp  Board's  selection of
auditors and the NBT Bancorp  Employee  Stock  Purchase  Plan,  but not upon the
issuance  of NBT  Bancorp  stock in the  merger and  ratification  of the merger
agreement. Instead, NBT Bancorp adjourned its stockholders' meeting with respect
to their  consideration  of the stock  issuance and  ratification  of the merger
agreement  to June 20,  2000 at which  time the NBT  Bancorp  stockholders  will
consider  and vote upon the stock  issuance  and merger  agreement  with Pioneer
American.

     WE ENCLOSE A NEW PROXY CARD  RESPECTING  THE MERGER BETWEEN NBT BANCORP AND
PIONEER  AMERICAN.  IF YOU HAVE ALREADY COMPLETED AND RETURNED THE PROXY CARD WE
SENT TO YOU WITH THE APRIL 3, 2000  MATERIALS AND YOU DO NOT WISH TO CHANGE YOUR
VOTE ON THE  MERGER  BETWEEN  NBT  BANCORP  AND  PIONEER  AMERICAN,  YOU NEED DO
NOTHING.  YOUR  PREVIOUSLY  SUBMITTED  PROXY  CARD  WILL BE  VOTED  AS YOU  HAVE
DIRECTED.  IF,  HOWEVER,  YOU WISH TO CHANGE YOUR VOTE ON THE MERGER BETWEEN NBT
BANCORP AND PIONEER AMERICAN, PLEASE COMPLETE THE ENCLOSED PROXY CARD AND RETURN
IT TO US PROMPTLY.  IF YOU HAVE NOT YET VOTED ON THE MERGER  BETWEEN NBT BANCORP
AND PIONEER  AMERICAN  AND WISH TO DO SO AT THE PRESENT  TIME,  YOU MAY COMPLETE
EITHER THE EARLIER  PROXY CARD OR THE  ENCLOSED  PROXY CARD AND RETURN IT IN THE
ACCOMPANYING POSTAGE-PAID ENVELOPE.

     We encourage you to read this entire  document  carefully.  This supplement
incorporates  important business and financial information about NBT Bancorp and
Pioneer  American that is not included in or delivered with this  document.  See
"Where You Can Find More Information" on page   .


/s/ Daryl R. Forsythe                    /s/ John W. Reuther
- ---------------------                    -------------------

Daryl R. Forsythe                        John W. Reuther
President and Chief Executive Officer    President and Chief Executive Officer
NBT Bancorp Inc.                         Pioneer American Holding Company Corp.


<PAGE>


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

     THE SHARES OF NBT BANCORP  COMMON STOCK OFFERED BY THIS  SUPPLEMENT 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
BANCORP COMMON STOCK.

Joint proxy  statement/prospectus  supplement dated May , 2000, and first mailed
to stockholders on or about May , 2000.


<PAGE>


                                NBT Bancorp Inc.
                              52 South Broad Street
                             Norwich, New York 13815

               NOTICE OF ADJOURNED ANNUAL MEETING OF STOCKHOLDERS

     NBT Bancorp  Inc., a Delaware  corporation,  will  reconvene  its adjourned
annual  meeting of  stockholders  at the Holiday Inn Arena,  2-8 Hawley  Street,
Binghamton,  New York on June 20, 2000 at 2:00 p.m. local time for the following
purposes:

     1. To consider and vote upon a proposal to issue  approximately 5.2 million
shares of NBT common stock in the merger and to ratify the Agreement and Plan of
Merger,  dated as of December 7, 1999, and amended as of March 7, 2000,  between
NBT and Pioneer  American  Holding  Company Corp.,  a Pennsylvania  corporation,
which will approve the merger and the following  actions described in the merger
agreement:

          Pioneer  American  will merge with a subsidiary  of NBT,  with Pioneer
          American being the surviving corporation,

          Following the first merger,  Pioneer American will merge with and into
          NBT, with NBT being the surviving corporation, and

          NBT will issue approximately 5.2 million shares of common stock to the
          former Pioneer American stockholders upon completion of the merger.

     2. To  transact  such other  business as may  properly  come before the NBT
reconvened annual meeting.

     FOR MORE  INFORMATION  ABOUT THE  MERGER,  PLEASE  REVIEW  THE JOINT  PROXY
STATEMENT/PROSPECTUS  THAT WE  PREVIOUSLY  SENT TO YOU AND THE MERGER  AGREEMENT
ATTACHED AS APPENDIX A TO THAT DOCUMENT.

     Whether or not you plan on attending the reconvened annual meeting,  if you
have not already  voted on the merger  between  NBT and Pioneer  American or if,
after   reviewing   the    accompanying    supplement   to   the   joint   proxy
statement/prospectus  you wish to change your vote on the merger between NBT and
Pioneer American,  please complete,  sign and date the enclosed proxy and return
it promptly in the accompanying postage-paid envelope. If you have already voted
on the merger  between NBT and Pioneer  American  and do not wish to change your
vote, you need not return another proxy. Your previously  returned proxy will be
voted in the manner you have specified.

     The board of directors of NBT  unanimously  recommends  that you vote "FOR"
approval of the issuance of NBT common stock in the merger with Pioneer American
and  ratification  of the merger  agreement,  the  merger and the other  matters
contemplated by the merger agreement.  The affirmative vote of a majority of the
shares of NBT  common  stock  present  and voting  and  entitled  to vote at the
meeting is required to approve  the  issuance of NBT common  stock in the merger
with Pioneer American and the merger agreement and related matters.

                                          By Order of the Board of Directors of
                                          NBT Bancorp Inc.


                                          /s/ Daryl R. Forsythe
                                          -----------------

                                          Daryl R. Forsythe
                                          President and Chief Executive Officer

Norwich, New York
May     , 2000

                     PIONEER AMERICAN HOLDING COMPANY CORP.
                              41 NORTH MAIN STREET


<PAGE>


                         CARBONDALE, PENNSYLVANIA 18407

               NOTICE OF ADJOURNED SPECIAL MEETING OF STOCKHOLDERS

     Pioneer  American Holding Company Corp., a Pennsylvania  corporation,  will
reconvene its adjourned  special  meeting of  stockholders  at Heart Lake Lodge,
1299 Heart Lake Road, Jermyn,  Pennsylvania on June 20, 2000 at 10:00 a.m. local
time for the following purposes:

     1. To consider and vote upon a proposal to adopt the  Agreement and Plan of
Merger,  dated as of December 7, 1999,  and amended as of March 7, 2000,  by and
between Pioneer  American and NBT Bancorp Inc., a Delaware  corporation,  and to
approve the merger and other transactions described in the merger agreement; and

     2. To transact such other  business as may properly come before the Pioneer
American reconvened special meeting.

     FOR MORE  INFORMATION  ABOUT THE  MERGER,  PLEASE  REVIEW  THE JOINT  PROXY
STATEMENT/PROSPECTUS  THAT WE  PREVIOUSLY  SENT TO YOU AND THE MERGER  AGREEMENT
ATTACHED AS APPENDIX A.

     The board of directors of Pioneer  American  recommends that you vote "FOR"
approval of the merger agreement,  the merger and the other matters contemplated
by the  merger  agreement.  The  affirmative  vote  of  seventy  percent  of the
outstanding  shares of Pioneer  American  common  stock  entitled to vote at the
meeting is required to approve the merger agreement and related matters. Pioneer
American  stockholders  have a right to dissent to the merger  agreement  and to
obtain  payment in cash of the fair value of their  Pioneer  American  shares by
complying  with the  procedures  described  in the April 3,  2000,  joint  proxy
statement/prospectus we previously sent to you.

     Whether or not you plan on attending the reconvened special meeting, if you
have not already  voted on the merger  between  NBT and Pioneer  American or if,
after   reviewing   the    accompanying    supplement   to   the   joint   proxy
statement/prospectus  you wish to change your vote on the merger between NBT and
Pioneer American,  please complete,  sign and date the enclosed proxy and return
it promptly in the enclosed postage-paid  envelope. If you have already voted on
the merger between NBT and Pioneer American and do not wish to change your vote,
you need not return another proxy. Your previously  returned proxy will be voted
in the manner you have specified.

                                    By Order of the Board of Directors of
                                    Pioneer American Holding Company Corp.


                                    /s/ John W. Reuther
                                    -------------------
                                    John W. Reuther
                                    President and Chief Executive Officer

Carbondale, Pennsylvania
May     , 2000



<PAGE>


QUESTIONS AND ANSWERS ABOUT THE ADJOURNED  STOCKHOLDERS'  MEETINGS

Q: WHAT IS THE PURPOSE OF THIS SUPPLEMENT?

A: Since our mailing of the joint proxy  statement/prospectus  on April 5, 2000,
NBT has  signed  an  agreement  to merge  with  BSB.  Because  that  merger,  if
completed,  would significantly alter the size and scope of NBT and its business
operations,  we have  determined to delay the  consideration  of and vote by our
stockholders  on the merger between NBT and Pioneer  American and to furnish our
respective  stockholders with information  regarding the proposed merger between
NBT and BSB in order  that our  stockholders  might  be  better  able to make an
informed judgment regarding the merger between NBT and Pioneer American.

Q: HAVE THE TERMS OF THE MERGER BETWEEN NBT AND PIONEER AMERICAN CHANGED?

A: No. The terms of the merger agreement between NBT and Pioneer American remain
the same. See "What Pioneer  American  Stockholders  Will Receive as a Result of
the Merger," below.

Q: AT OUR RESPECTIVE MEETINGS, ARE WE TO VOTE ON THE PROPOSED NBT-BSB MERGER?

A: No. We are  holding our  respective  stockholders'  meetings  only so you can
consider and vote upon the merger between NBT and Pioneer American. You will not
vote on the merger between NBT and BSB at our respective June 20, 2000 meetings.
Only at some time in the future will NBT  stockholders  be requested to consider
and vote upon the  proposed  merger  between  NBT and BSB.  Separately  from the
consideration of our merger,  NBT and BSB will prepare  disclosure  material for
the stockholders of NBT and BSB regarding that proposed merger.

Q: MUST I RETURN ANOTHER PROXY CARD?

A: No. After you have carefully read this supplement, you need do nothing if you
have already returned your proxy card and do not wish to change your vote on the
merger between NBT and Pioneer American.  If, however, you have not yet voted on
the merger between NBT and Pioneer  American and you wish to vote now, or if you
wish to change your vote on the merger between NBT and Pioneer American,  please
indicate on the enclosed  proxy card how you want your shares to be voted,  then
sign,  date and mail it in the  accompanying  postage-paid  envelope  as soon as
possible so that your shares may be represented  and voted at the NBT reconvened
annual meeting or the Pioneer American  reconvened special meeting.  If you sign
and send in your proxy and do not indicate how you want to vote, your proxy will
be counted as a vote in favor of the proposal.

Q: CAN I CHANGE MY VOTE AFTER I HAVE MAILED MY SIGNED PROXY CARD?

A: Yes.  There are three ways for you to revoke your proxy and change your vote.
First, you may send a later-dated,  signed proxy card before the meeting of your
company.  Second,  you may  attend  your  company's  meeting in person and vote.
Third, you may revoke any proxy by written notice to the Chief Executive Officer
of NBT or Pioneer American, as appropriate,  prior to your company's meeting. If
you have  instructed  a broker to vote your shares,  you must follow  directions
received from your broker to change your vote.

Q: WHOM  SHOULD I CALL WITH  QUESTIONS  OR TO OBTAIN  ADDITIONAL  COPIES OF THIS
SUPPLEMENT OR COPIES OF THE JOINT PROXY STATEMENT/PROSPECTUS?

NBT Bancorp Inc.                     Pioneer American Holding Company Corp.
52 South Broad Street                41 North Main Street
Norwich, New York  13815             Carbondale, Pennsylvania  18407
Attention: Michael J. Chewens, CPA   Attention: Patricia A. Cobb, Esq.
Phone Number: (607) 337-6520         Phone Number: (570) 282-8045


                                       i

<PAGE>


                                TABLE OF CONTENTS

<TABLE>
<S>                                                                                    <C>
QUESTIONS AND ANSWERS ABOUT THE ADJOURNED STOCKHOLDERS' MEETINGS                         i

The Adjourned Stockholders' Meetings                                                     2

What Pioneer American Stockholders Will Receive as a Result of the Merger                3

Proposed Merger Between NBT and BSB                                                      4

Revised Fairness Opinions by Financial Advisors                                          6
         Opinion of NBT's Financial Advisor                                              6
         Opinion of Pioneer American's Financial Advisor                                11

Price Range of Common Stock and Dividends                                               15

Experts                                                                                 16

Where You Can Find More Information                                                     16

UNAUDITED PRO FORMA COMBINED FINANCIAL STATEMENTS                                       17

NOTES TO UNAUDITED PRO FORMA COMBINED FINANCIAL STATEMENTS                              23

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS                               26

APPENDIX A
         Fairness Opinion of McConnell, Budd & Downes, Inc.

APPENDIX B
         Fairness Opinion of Danielson Associates Inc.
</TABLE>



<PAGE>


                      THE ADJOURNED STOCKHOLDERS' MEETINGS

NBT. The adjourned annual meeting of NBT stockholders  will be reconvened at the
Holiday Inn Arena, 2-8 Hawley Street,  Binghamton,  New York at 2:00 p.m., local
time, on Tuesday,  June 20, 2000. At our reconvened annual meeting,  we will ask
that you consider and vote upon

     the issuance of approximately 5.2 million shares of NBT common stock in the
     merger  between  NBT  and  Pioneer  American  and the  ratification  of the
     Agreement and Plan of Merger,  dated as of December 7, 1999, and amended as
     of March 7, 2000, between NBT and Pioneer American,  which will approve the
     merger and the following actions described in the merger agreement:

          Pioneer  American  will merge with a subsidiary  of NBT,  with Pioneer
          American being the surviving corporation,

          Following the first merger,  Pioneer American will merge with and into
          NBT, with NBT being the surviving corporation, and

          NBT will issue approximately 5.2 million shares of common stock to the
          former Pioneer American stockholders upon completion of the merger.

Additionally,  we will transact such other  business as may properly come before
the NBT reconvened annual meeting.  For a more comprehensive  description of the
merger  agreement,  the merger  and  related  transactions,  we refer you to our
discussion   of   these   matters   which    appeared   in   our   joint   proxy
statement/prospectus, dated April 3, 2000.

     Only  holders of record of NBT  common  stock at the close of  business  on
April 3, 2000,  which is the record  date for the NBT  annual  meeting,  will be
entitled  to  vote  at  the  NBT  reconvened  annual  meeting  and  any  further
adjournments of the meeting.  You can cast one vote for each share of NBT common
stock  that you owned on the record  date for each  matter  proposed  at the NBT
reconvened annual meeting.

     Approval  of NBT's  issuance of its common  stock to the  Pioneer  American
stockholders  in the  merger  and  ratification  of  the  merger  agreement  and
completion of the merger require, among other things, approval by the holders of
a majority of the shares of NBT common stock  present and voting and entitled to
vote at the NBT adjourned annual meeting.  We will count the vote of all proxies
received by us since we mailed our proxy  materials,  if those  proxies have not
since been  revoked.  In order to have a quorum,  a majority of the total voting
power of the  outstanding  shares of NBT's common stock  entitled to vote at the
NBT annual meeting must be represented in person or by proxy.

     The NBT Board  believes  that the merger is fair to you and is in your best
interests,  and unanimously recommends that you vote FOR the proposal to approve
the  issuance  of NBT  common  stock in the  merger  and to  ratify  the  merger
agreement, the merger and the related matters.

Pioneer American. The adjourned special meeting of Pioneer American stockholders
will  be  reconvened  at  Heart  Lake  Lodge,  1299  Heart  Lake  Road,  Jermyn,
Pennsylvania  at 10:00 a.m.,  local  time,  on Tuesday,  June 20,  2000.  At our
reconvened special meeting, we will ask that you consider and vote upon

     a proposal to adopt the Agreement and Plan of Merger,  dated as of December
     7, 1999, and amended as of March 7, 2000, by and between  Pioneer  American
     and NBT Bancorp Inc., a Delaware corporation, and to approve the merger and
     other transactions described in the merger agreement.


Additionally,  we will transact such other  business as may properly come before
the  Pioneer  American  reconvened  special  meeting.  For a more  comprehensive
description of the merger  agreement,  the merger and related  transactions,  we
refer you to our  discussion of these matters which  appeared in our joint proxy
statement/prospectus, dated April 3, 2000.


                                       2

<PAGE>


     Only  holders of record of Pioneer  American  common  stock at the close of
business on March 24,  2000,  which is the record date for the Pioneer  American
special  meeting,  will be entitled to vote at the Pioneer  American  reconvened
special meeting and any further  adjournments  of the meeting.  You can cast one
vote for each  share of  Pioneer  American  common  stock  that you owned on the
record date for each matter proposed at the Pioneer American  reconvened special
meeting.

     Approval of the merger  agreement  and  completion  of the merger  require,
among  other  things,  approval  by  the  holders  of  seventy  percent  of  the
outstanding  shares of Pioneer  American  common stock entitled to vote. We will
count  the  vote of all  proxies  received  by us  since  we  mailed  our  proxy
materials,  if those  proxies  have not since been  revoked.  In order to have a
quorum,  a  majority  of the total  voting  power of the  outstanding  shares of
Pioneer  American's common stock entitled to vote at the Pioneer American annual
meeting must be represented in person or by proxy.

     The Pioneer  American  Board believes that the merger is fair to you and is
in your  best  interests,  and  unanimously  recommends  that  you  vote FOR the
proposal to approve the merger agreement, the merger and the related matters.

   WHAT PIONEER AMERICAN STOCKHOLDERS WILL RECEIVE AS A RESULT OF THE MERGER

THE EXCHANGE RATIO.  Pioneer American  stockholders will receive 1.805 shares of
NBT common stock for each share of Pioneer American common stock that they own.

TERMINATION  UPON A DECLINE IN THE VALUE OF NBT COMMON STOCK.  Pioneer  American
has the right to cancel the merger if:

     the price of a share of NBT common stock declines below $15.00 and

     the NBT stock price  decline,  expressed as a  percentage,  is more than 15
     percentage  points greater than the weighted average stock price decline of
     the index group.

     The price per NBT share of $15.00  represents a 10.45% decline in the price
per NBT  share  of  $16.75  which is the  share  price  used by NBT and  Pioneer
American in their negotiation of the merger agreement. Even if both of these two
conditions  were  present  and  Pioneer  American  were to decide to cancel  the
merger,  NBT could require Pioneer American to complete the merger by increasing
the  number of shares of NBT  common  stock to be issued to  Pioneer  American's
stockholders,  so that a Pioneer  American  stockholder  would  receive at least
$27.08 worth of NBT stock for each share of Pioneer American common stock.

     In order to determine the price and percentage  decline in the value of the
NBT common stock and of the weighted  average stock price of the index group, we
will take the  average  of the  closing  bid and asked  prices per share for NBT
common  stock  and for the  companies  in the  index  group  for  each of the 20
consecutive  trading days ending on the eighth trading day before the day chosen
to be the effective date of the merger.

     As of the date of this supplement,  [EACH  CONDITION/ONLY ONE CONDITION] is
present to the right of Pioneer  American to cancel the merger (assuming for the
sake of  illustration  that the effective  date of the merger were seven trading
days after the date of this supplement).  Consequently, under current conditions
and assumptions, the Pioneer American Board would [not] have the right to cancel
the merger agreement. In the event Pioneer American were to terminate the merger
agreement  under  the  provisions  referenced  in this  section,  action  by the
stockholders  of Pioneer  American would not be required.  Neither the NBT Board
nor the  Pioneer  American  Board has made a  decision  as to  whether  it would
exercise its rights under the merger  agreement  under such  circumstances.  The
respective  boards of NBT and  Pioneer  American  would make such a decision  in
light of the  circumstances  existing at the time that the respective  board has
the  opportunity  to make  such  an  election,  if  any.  Prior  to  making  any
determination  to exercise their respective  rights under the merger  agreement,
the Boards would consult their respective financial and other advisors and would
consider all financial and other information deemed relevant to their respective
decisions.  There can be no  assurance  that the  Boards  would  exercise  their
respective  rights under the merger  agreement if the conditions set forth above
were applicable. If the Pioneer American Board were not to elect to exercise its
right to

                                       3
<PAGE>


terminate  the  merger  agreement  under  the  circumstances  discussed  in this
section,  the  exchange  ratio  would  be  1.805  and the  dollar  value  of the
consideration  which the stockholders of Pioneer American would receive for each
share of Pioneer American common stock would be the value of 1.805 shares of NBT
common stock at the effective time of the merger.

     PROPOSED MERGER BETWEEN NBT AND BSB

ANNOUNCEMENT OF MERGER WITH BSB. On April 20, 2000, NBT and BSB Bancorp, Inc., a
Delaware corporation, announced that they had entered into an Agreement and Plan
of Merger,  dated as of April 19, 2000.  In this  section and  elsewhere in this
supplement,  we refer to the merger agreement between NBT and BSB as the "merger
agreement with BSB" and the resulting merger as the "merger with BSB."

     Under the merger agreement with BSB, BSB and NBT will merge, with NBT being
the  surviving  corporation.  The  surviving  corporation  will  have  assets of
approximately $4.7 billion. NBT and BSB will choose a new name for the surviving
corporation  before the merger with BSB occurs.  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.  Stockholders of BSB will receive two
shares of NBT  common  stock for each  share  exchanged.  Based on the April 19,
2000,  closing  price of NBT common  stock on the Nasdaq  National  Market,  the
transaction  is valued at $251  million or $24.00 per share for the  outstanding
common  stock of BSB.  Based on the  closing  price of NBT  common  stock on the
Nasdaq National Market of $ per share on May , 2000, the most recent practicable
date prior to the mailing of this supplement,  the transaction is valued at $ or
$ per share for the outstanding  common stock of BSB. The merger with BSB, which
has been  unanimously  approved  by the boards of  directors  of NBT and BSB, is
subject  to  the  approval  by  each  company's   stockholders  and  by  banking
regulators. NBT anticipates the merger will close in the fourth quarter of 2000.
NBT intends the merger with BSB to be  accounted  for as a  pooling-of-interests
and to qualify as a tax-free exchange for BSB stockholders.

     BSB has  provided  NBT an  option  to  acquire  a number of shares of BSB's
common stock equal to 19.9% of BSB's common  stock  outstanding  as of the first
date the option becomes  exercisable;  the option is exercisable in the event of
certain circumstances  involving  transactions with third parties, acts of third
parties,  or break-up of the merger  agreement with BSB. NBT has provided BSB an
option to  acquire a number of shares of NBT's  common  stock  equal to 19.9% of
NBT's  common  stock  outstanding  as of  the  first  date  the  option  becomes
exercisable;  the option is  exercisable  in the event of certain  circumstances
involving transactions with third parties, acts of third parties, or break-up of
the merger agreement with BSB.

MERGER OF BANKING SUBSIDIARIES. Immediately following the merger with BSB, NBT's
and BSB's principal  banking  subsidiaries,  NBT Bank, N.A. 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 the merger with BSB.

MANAGEMENT  OF THE SURVIVING  CORPORATION  FOLLOWING THE MERGER OF NBT 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 NBT from the members of its board,
plus one designated by NBT from NBT's newly  acquired Lake Ariel  Bancorp,  Inc.
Pennsylvania  subsidiary  who is serving on the NBT Board and one  designated by
NBT from  Pioneer  American  who is  serving  on the NBT  Board,  subject to the
closing of the merger of NBT and Pioneer  American.  If we do not consummate the
merger between NBT and 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 NBT, and one former
Lake Ariel board member who is serving on the NBT Board.  This former Lake Ariel
board member will be designated by NBT. Upon  completion of the merger with BSB,
common  stockholders of NBT will have ownership of  approximately  53 percent of
the surviving corporation while BSB's common stockholders will own approximately
47  percent,  assuming  consummation  of the  merger  between  NBT  and  Pioneer
American.

                                       4
<PAGE>


     Daryl R.  Forsythe,  president  and chief  executive  officer of NBT,  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.
NBT Bank's  president and chief  operating  officer,  Martin A.  Dietrich,  will
become the president and chief operating officer of the surviving bank.  Michael
J. Chewens,  executive vice president and chief  financial  officer of NBT, 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.  Other major bank  functions  will be conducted  from the  surviving
corporation's  Norwich,  Binghamton and Scranton locations  following the merger
with BSB.

IMPACT OF MERGER WITH BSB UPON PIONEER AMERICAN STOCKHOLDERS.  The completion of
the proposed  merger with BSB will change the results of the merger  between NBT
and Pioneer  American in a number of ways. For ease of reference,  we will refer
in this heading to the merger agreement  between NBT and Pioneer American as the
"NBT/PA Agreement."

          The NBT/PA Agreement  provides that,  following the merger between NBT
          and Pioneer  American,  the NBT Board will consist of the directors of
          NBT immediately  prior to the merger between NBT and Pioneer  American
          (of whom there are currently  twelve) and three other  individuals who
          are currently members of the Pioneer American Board, Messrs. Joseph G.
          Nasser,  Gene  E.  Goldenziel  and  Richard  Chojnowski.   The  merger
          agreement  with BSB provides  that  following the merger with BSB (and
          assuming  completion of the NBT and Pioneer American merger),  the NBT
          Board will consist of 15 directors, seven of whom will be designees of
          BSB,  six will be  designees  of NBT,  one will be a former Lake Ariel
          director  who at the  time  of the  merger  with  BSB  will  be an NBT
          director,  and one will be a former Pioneer  American  director who at
          the time of the merger with BSB will be an NBT director.  Accordingly,
          following  the  merger  between  NBT and  Pioneer  American  and until
          completion  of the merger  with BSB,  the NBT Board will  consist of a
          number of directors  currently  contemplated  as being 15 and three of
          those  directors will be Messrs.  Nasser,  Goldenziel and  Chojnowski.
          Upon  completion of the merger with BSB, the board of directors of the
          surviving  corporation  will be  reconstituted  and  only  one  former
          Pioneer  American  director  will at that  time be a  director  of the
          surviving corporation.

          In our joint  proxy  statement/prospectus,  dated  April 3,  2000,  we
          stated that following the merger between NBT and Pioneer  American the
          former  stockholders of Pioneer American would own  approximately  5.2
          million  shares  of NBT  common  stock,  or  approximately  22% of the
          outstanding  stock  of the  combined  company.  Following  the  merger
          between NBT and Pioneer American,  the surviving corporation will have
          consolidated  assets of approximately  $2.4 billion and  stockholders'
          equity of  approximately  $182 million (as of December 31, 1999,  on a
          pro forma combined basis). Upon completion of the merger with BSB, the
          former   Pioneer   American   stockholders   would   continue  to  own
          approximately  5.2  million  shares of common  stock of the  surviving
          corporation  (assuming for the sake of argument that no former Pioneer
          American  stockholder  will  have  sold  any of his or her NBT  shares
          following  completion of the merger between NBT and Pioneer American).
          This number of shares of common stock of the surviving  corporation in
          the hands of former  Pioneer  American  stockholders  would  represent
          approximately  12%  of  the  outstanding  shares  of  the  surviving
          corporation  following  the merger with BSB.  Upon  completion  of the
          merger with BSB,  the  surviving  corporation  will have  consolidated
          assets of  approximately  $4.7  billion  and  stockholders'  equity of
          approximately $325.0 million.

     NBT, as the  surviving  corporation  in the merger with BSB,  expects that,
after  completion of that merger and subject to approval and  declaration by its
Board,  it will  continue  its current  dividend  policy and  declare  regularly
scheduled  quarterly cash dividends on the shares of its common stock consistent
with past practices. The current annualized rate of cash dividends on the shares
of NBT common stock is $0.68 per share.

                                       5
<PAGE>

                 REVISED FAIRNESS OPINIONS BY FINANCIAL ADVISORS

OPINION OF NBT'S FINANCIAL ADVISOR

     On December 7, 1999, McConnell,  Budd & Downes, Inc. ("MB&D") delivered its
opinion to the NBT Board,  that as of that date,  the  exchange  ratio was fair,
from a  financial  point  of view to NBT  stockholders.  The  basis  for  MB&D's
opinion,  which is  unchanged,  has been  updated for the purposes of this joint
proxy  statement/prospectus  and appears in Appendix A. The  exchange  ratio was
negotiated based on consideration of numerous factors including the following:

          An analysis of the possible  future earnings per share results for the
          parties on both a combined and a stand-alone basis.

          Anticipated   dilutive  or  accretive   effects  of  the   prospective
          transaction to the earnings per share of NBT.

          Probable  impact  on  dividends  payout  ratio  as  a  result  of  the
          contemplated transaction.

          Loan  portfolios  and  relative  asset  quality  as  disclosed  by the
          parties.

          Adequacy of reserves for loan and lease losses of the parties.

          Composition of the deposit bases of each of the parties.

          Analysis of the historical trading range, trading pattern and relative
          liquidity of the common shares of each of the parties.

          Accounting equity  capitalization,  the tangible equity capitalization
          and the market capitalization of each of the parties.

          Contemplation of other factors, including certain intangible factors.

     MB&D has acted as  financial  advisor to NBT on a  contractual  basis since
October 20, 1994 in connection with NBT's development and  implementation of its
strategic plan and has assisted NBT in the  evaluation of numerous  hypothetical
affiliation  opportunities with banks, thrifts and other financial  institutions
since that date.  With  respect to the  pending  transaction  involving  Pioneer
American, MB&D advised NBT during the evaluation and negotiation process leading
up to the  execution of the merger  agreement  and provided NBT with a number of
analyses  as  to  a  range  of  financially   feasible   exchange  ratios.   The
determination of the applicable  exchange ratio was arrived at in an arms-length
negotiation  between NBT and Pioneer American in a process in which MB&D advised
NBT and participated directly in the negotiations.

     MB&D  was  retained  based  on its  qualifications  and  experience  in the
financial analysis of banking and thrift institutions  generally,  its knowledge
of the New York and Pennsylvania  banking markets in particular,  as well as its
experience  with  merger  and   acquisition   transactions   involving   banking
institutions.  As a part of its investment  banking  business,  which is focused
exclusively on financial  services  industry  participants,  MB&D is continually
engaged in the  valuation  of financial  institutions  and their  securities  in
connection  with  its  equity  brokerage  business  generally  and  mergers  and
acquisitions in particular.  Members of the Corporate  Finance Advisory Group of
MB&D have  extensive  experience in advising  financial  institution  clients on
mergers and  acquisitions.  In the  ordinary  course of its  business as an NASD
broker-dealer,  MB&D may, from time to time,  purchase  securities  from or sell
securities to NBT or Pioneer American and as a market maker in securities.  MB&D
may from time to time have a long or short  position in, and buy or sell debt or
equity  securities  of NBT or Pioneer  American  for its own  account or for the
accounts of its customers.  In addition, in the ordinary course of business, the
employees of MB&D may have direct or indirect  investments in the debt or equity
securities of either or both NBT or Pioneer American.

     The full text of the opinion,  which sets forth assumptions  made,  matters
considered and limits on the review  undertaken,  is attached hereto as Appendix
A. MB&D urges that all NBT shareholders read the opinion in its entirety and the
joint  proxy  statement/prospectus  in its  entirety.  The  opinion  of  MB&D is
directed only to the

                                       6
<PAGE>

exchange ratio at which shares of Pioneer American common stock may be exchanged
for shares of NBT  common  stock.  The  opinion  of MB&D does not  constitute  a
recommendation  to any holder of NBT common  stock as to how such holder  should
vote at the NBT annual  meeting.  The  summary of the  opinion  and the  matters
considered   in  the   MB&D   analysis   set   forth   in   this   joint   proxy
statement/prospectus  is  qualified  in its entirety by reference to the text of
the opinion itself.  The opinion is necessarily  based upon conditions as of the
date of the opinion and upon information made available to MB&D through the date
thereof.  No limitations were imposed by the NBT Board upon MB&D with respect to
the investigations made, matters considered or procedures followed in the course
of rendering its opinions.

Materials Reviewed by MB&D:

     In connection with the rendering and updating of its opinion, MB&D reviewed
the following documents and considered the following subjects:

          The merger agreement detailing the pending transaction;

          The joint proxy  statement/prospectus  in substantially the form to be
          mailed to NBT shareholders;

          Pioneer  American  Annual Reports to  stockholders  for 1996, 1997 and
          1998;

          Pioneer American Annual Reports on Form 10-K for 1996, 1997 and 1998;

          Related  financial  information  for the three  calendar  years  ended
          December 31, 1996, 1997, and 1998 for Pioneer American;

          Pioneer American  Quarterly Report on Form 10-Q and related  unaudited
          financial information for the first three quarters of 1999;

          Pioneer American's press release concerning  unaudited results for the
          calendar years 1998 and 1999;

          NBT Annual Reports to Stockholders for 1996, 1997 and 1998;

          NBT Annual Reports on Form 10-K and related financial  information for
          the calendar years ended 1996, 1997 and 1998;

          NBT  Quarterly  Reports on Form 10-Q and related  unaudited  financial
          information for the first three quarters of 1999;

          NBT's press  release  concerning  unaudited  results for the  calendar
          years 1998 and 1999;

          Internal financial  information and financial  forecasts,  relating to
          the  business,  earnings,  cash  flows,  assets and  prospects  of the
          respective  companies  furnished  to MB&D by Pioneer  American and NBT
          respectively;

          Discussions with members of the senior  management of Pioneer American
          concerning  the past and  current  results  of  operations  of Pioneer
          American,  its current financial condition and management's opinion of
          its future prospects;

          Discussions  with members of the senior  management of NBT  concerning
          the past  and  current  results  of  operations  of NBT,  its  current
          financial condition and management's opinion of its future prospects;

          The historical record of reported prices,  trading volume and dividend
          payments for both Pioneer American and NBT common stock;

                                       7
<PAGE>

          Based  primarily on anecdotal  information,  the current  state of and
          future  prospects  for  the  economy  of  New  York  and  northeastern
          Pennsylvania  generally  and the  relevant  market  areas for  Pioneer
          American and NBT in particular;

          Specific  merger  analysis  models   developed  by  MB&D  to  evaluate
          potential business  combinations of financial  institutions using both
          historical  reported  information  and projected  information for both
          Pioneer  American  and NBT and the  results  of  application  of these
          models;

          The reported financial terms of selected recent business  combinations
          of financial  institutions  for purposes of  comparison to the pending
          transaction;

          Such other studies and analyses as MB&D considered  appropriate  under
          the circumstances associated with this particular transaction.

     The opinion of MB&D takes into account its assessment of general  economic,
market  and  financial  conditions  and its  experience  in  other  transactions
involving  participants  in the  financial  services  industry,  as  well as its
experience  in securities  valuation  and its knowledge of the banking  industry
generally.  For purposes of reaching  its  opinion,  MB&D has assumed and relied
upon the accuracy and  completeness  of the  information  provided to it or made
available by Pioneer American and NBT and does not assume any responsibility for
the  independent  verification  of such  information.  With respect to financial
forecasts  made  available to MB&D it is assumed by MB&D that they were prepared
on a reasonable  basis and reflect the best  currently  available  estimates and
good faith judgments of the management of Pioneer American and NBT respectively,
as to the future  performance of Pioneer  American and NBT. MB&D has also relied
upon assurances of the management of Pioneer American and NBT that they were not
aware  of any  facts  or of the  omission  of any  facts  that  would  make  the
information or financial forecasts provided to MB&D incomplete or misleading. In
the course of rendering  its opinion,  MB&D has not  completed  any  independent
valuation  or appraisal of any of the assets or  liabilities  of either  Pioneer
American or NBT and has not been  provided  with such  valuations  or appraisals
from any other source.

     The  following  is a summary of the material  analyses  employed by MB&D in
connection with rendering its written  opinion.  Given that it is a summary,  it
does not  purport  to be a complete  and  comprehensive  description  of all the
analyses  performed,  or an  enumeration  of every matter  considered by MB&D in
arriving at its opinion.  The preparation of a fairness opinion is a complicated
process,  involving a  determination  as to the most  appropriate  and  relevant
methods  of  financial  analysis  and the  application  of those  methods to the
particular circumstances.  Therefore, such an opinion is not readily susceptible
to a summary  description.  In arriving at its  fairness  opinion,  MB&D did not
attribute  any  particular  weight  to  any  one  specific  analysis  or  factor
considered by it and made  qualitative as well as  quantitative  judgments as to
the significance of each analysis and factor.  Therefore, MB&D believes that its
analyses must be considered as a whole and feels that  attributing  undue weight
to any  single  analysis  or factor  considered  could  create a  misleading  or
incomplete view of the process  leading to the formation of its opinion.  In its
analyses,  MB&D has made certain  assumptions  with respect to banking  industry
performance, general business and economic conditions and other factors, many of
which are beyond the control of  management of either  Pioneer  American or NBT.
Estimates,  which are referred to in the analyses are not necessarily indicative
of actual  values or  predictive  of future  results or  values,  which may vary
significantly from those set forth. In addition, analyses relating to the values
of  businesses do not purport to be appraisals or to reflect the prices at which
businesses might actually be sold. Accordingly,  such analyses and estimates are
inherently  subject to uncertainty and MB&D does not assume  responsibility  for
the accuracy of such analyses or estimates.

BSB TRANSACTION

     On  April  20,  2000,  NBT  announced  that it had  executed  a  definitive
agreement  to merge with BSB.  MB&D has reviewed the  agreement  with BSB.  MB&D
acted as NBT's  financial  advisor  throughout  the  negotiations  with BSB. The
agreement  with BSB does not alter MB&D's  opinion  concerning  the  NBT/Pioneer
American transaction. MB&D continues to maintain the opinion that as of the date
of this post-effective  amendment, the exchange ratio with respect to the merger
between NBT and Pioneer American is fair, from a financial point of view, to NBT
stockholders.

Analysis of the Anticipated Merger and the Fixed Exchange Ratio:

                                       8
<PAGE>


     The  consideration of 1.805 shares of NBT common stock,  valued at the last
sale  price  of NBT on the day  prior  to the  announcement  of the  transaction
($16.25) represents the following values and multiples:

    Total Transaction Value:                             $85,337,277
    Deal Premium to Pioneer American's last trade:       5.70%
    Deal Price / EPS for the last 12 months              20.95x
    Deal Price / Tangible Book as of 9/30/99             2.68x

Contribution Analysis:

     The following  table reflects the acquisition of Lake Ariel on February 17,
2000 and is based on reported  financial data for Pioneer American and NBT as of
September 30, 1999 and the per share price of NBT as of December 6, 1999.  Under
those circumstances,  the relative contributions of the parties to the pro forma
NBT on a pooling basis would have been as follows:

                          Pro Forma Contribution Table

                                  As of 9-30-99

<TABLE>
<CAPTION>
               Item                                      NBT                 Pioneer American
             --------                                  -------              ------------------
<S>                                                   <C>                  <C>
Proposed Ownership                                      77.3%                     22.7%
Assets                                                  82.1%                     17.9%
Loans                                                   83.1%                     16.9%
Deposits                                                82.5%                     17.5%
Equity                                                  83.6%                     16.4%
Tangible Equity                                         83.1%                     16.9%
Estimated Net Income of Combined                        80.7%                     19.3%
 Company for fiscal year 2000.
Estimated  Net  Income of  Combined  Company            76.7%                     23.3%
 for fiscal year 2001.
</TABLE>

Specific Acquisition Analysis:

     MB&D  employs  a  proprietary  analytical  model  to  examine  transactions
involving banking  companies.  The model uses forecast  earnings data,  selected
current  period  balance sheet and income  statement  data,  current  market and
trading  information  and a number  of  assumptions  as to  interest  rates  for
borrowed funds, the opportunity cost of funds, discount rates, dividend streams,
effective  tax rates and  transaction  structures.  The model  inquires into the
likely  economic  feasibility  of a given  transaction at a given price level or
specified exchange rate while employing a specified transaction  structure.  The
model also  permits  evaluation  of  various  levels of  potential  non-interest
expense   savings  which  might  be  achieved   along  with  various   potential
implementation  time  tables for such  savings,  as well as the  possibility  of
revenue enhancement opportunities which may arise in a given transaction.

     Utilizing  this model,  MB&D  prepared pro forma  analyses of the financial
impact of the merger to the NBT stockholders.  MB&D compared  estimated earnings
per share of NBT on a stand alone  basis for fiscal year 2000,  2001 and 2002 to
the estimated  earnings per share of the common stock of the combined company on
a pro forma basis for the same fiscal years.  MB&D's analysis  illustrates  that
the merger  will be  dilutive to  stockholders  of NBT on an earnings  per share
basis in fiscal year 2000, and becomes  accretive to NBT  stockholders in fiscal
year 2001. The  transaction  remains  accretive to stockholders of NBT in fiscal
year 2002.

Analysis of Other Comparable Transactions:

     MB&D  is  reluctant  to  place  emphasis  on  the  analysis  of  comparable
transactions as a valuation  methodology due to what it considers to be inherent
limitations of the application of the results to specific  cases.  MB&D believes
that such analysis fails to adequately take into consideration such factors as:

                                       9
<PAGE>


          Material   differences  in  the  underlying   capitalization   of  the
          comparable institutions which are being acquired;

          Differences in the historic  earnings (or loss)  patterns  recorded by
          the compared institutions which can depict a very different trend than
          might be implied by examining only recent financial results;

          Failure  to exclude  non-recurring  profit or loss items from the last
          twelve months'  earnings streams of target companies which can distort
          apparent earnings multiples;

          Material  differences  in the form or forms of  consideration  used to
          complete the transaction;

          Differences between the planned method of accounting for the completed
          transaction;

          Factors  such as:  the  relative  population,  business  and  economic
          demographics  of  the  acquired   entity's   markets  as  compared  or
          contrasted  to  such  factors  for the  markets  in  which  comparable
          companies are doing business.

     With  these  reservations  in  mind,  we  nonetheless  examined  statistics
associated with 46 transactions  (excluding the subject  transaction)  involving
commercial banks. The following criteria was utilized to create the sample:

          Acquired institutions are all commercial banks.

          Announced between June 1, 1998 and December 7, 1999.

          Announced  deal  value  greater  than $50  million  and less than $100
          million.

     The table which follows  permits a comparison of the mean and median values
for two selected  statistics arising from the list of 46 transactions  evaluated
with  the  "comparable"  statistics  calculated  for the  transaction  which  is
described in this joint proxy statement/prospectus.

              "Comparable" statistics as of the announcement date:

<TABLE>
<CAPTION>
          Compared statistics            Announced transaction price/tangible       Announced transaction price/
                                                      book value                    trailing 12 months earnings
<S>                                      <C>                                       <C>
NBT/Pioneer American                                     2.68x                                 20.95x
Sample (46 transactions)
                 Mean                                    3.07x                                 24.5x
                Median                                   3.08x                                 21.7x
1999 (29 transactions)
                 Mean                                    2.96x                                 23.7x
                Median                                   2.85x                                 21.5x
1998 (17 transactions)
                 Mean                                    3.23x                                 26.0x
                Median                                   3.19x                                 23.7x
PA, NJ & NY (8 transactions)
                 Mean                                    3.02x                                 26.6x
                Median                                   2.93x                                 25.0x
</TABLE>


COMPENSATION OF MB&D

     Pursuant to a letter  agreement with NBT dated December 7, 1999,  MB&D will
receive a fixed fee of $375,000. This fee will be divided into several payments,
which  correspond with the successful  completion of specific  events.  MB&D was
paid $75,000  after the  execution of the merger  agreement  and will be paid an
additional  $150,000  upon  issuance of its opinion which will be included as an
exhibit to this joint proxy statement/prospectus.  Payment of the balance of the
fee will be conditioned on closing of the transaction.

                                       10
<PAGE>


     The fee payable to MB&D represents  compensation  for services  rendered in
connection  with  the  analysis  of  the   transaction,   participation  in  the
negotiations,  participation  in the  drafting  of  documentation,  and  for the
rendering of its Opinion. In addition,  NBT has agreed to reimburse MB&D for its
reasonable  out-of-pocket  expenses incurred in connection with the transaction.
NBT also has agreed to indemnify MB&D and its directors,  officers and employees
against certain losses,  claims,  damages and liabilities relating to or arising
out of its engagement, including liabilities under the federal securities laws.

     MB&D has filed a written  consent with the SEC relating to the inclusion of
its  fairness  opinion  and the  reference  to such  opinion  and to MB&D in the
registration  statement  in  which  this  joint  proxy  statement/prospectus  is
included.  In giving such  consent,  MB&D did not admit that it comes within the
category of persons whose consent is required  under Section 7 of the Securities
Act of 1933 or the rules and  regulations  of the SEC  thereunder,  nor did MB&D
thereby admit that it is an expert with respect to any part of such Registration
Statement  within the meaning of the term "expert" as used in the Securities Act
of 1933 as amended, or the rules and regulations of the SEC thereunder.

OPINION OF PIONEER AMERICAN'S FINANCIAL ADVISOR

     Pioneer  American   retained   Danielson   Associates,   Inc.   ("Danielson
Associates") to advise the Pioneer  American Board of Directors as to its "fair"
sale value and the fairness to its  shareholders  of the financial  terms of the
offer to be acquired by NBT.  Danielson  Associates is regularly  engaged in the
valuation of banks, bank holding  companies,  and thrifts in the connection with
mergers,  acquisitions, and other securities transactions; and has knowledge of,
and  experience  with,  Pennsylvania  and New York  banking  markets and banking
organizations  operating in those markets.  Danielson Associates was selected by
Pioneer  American because of its knowledge of, expertise with, and reputation in
the financial services industry.

     On  April  20,  2000,  NBT  announced  an  equal  merger  with  BSB,  which
represented  a material  change,  and,  as a result,  required  an update of the
original  opinion that  included  the impact of the BSB merger.  This update was
delivered to the Board of Directors of Pioneer  American stating that as of that
time the financial terms of the NBT offer were still "fair" to Pioneer  American
and its shareholders.

     Danielson  Associates  reviewed the Pioneer  American-NBT  Merger Agreement
with respect to the pricing and other terms and  conditions  of the Merger,  but
the  decision  as to  accepting  the offer was  ultimately  made by the Board of
Directors of Pioneer American. Danielson Associates rendered its oral opinion to
the Pioneer  American  Board of Directors,  which it  subsequently  confirmed in
writing,  that as of the date of such opinion,  the  financial  terms of the NBT
offer were "fair" to Pioneer American and its shareholders.  No limitations were
imposed by the Pioneer  American Board of Directors  upon  Danielson  Associates
with respect to the investigation made or procedures  followed by it in arriving
at its opinion.

     In arriving at its original and updated opinions, Danielson Associates:

          Reviewed  certain  business  and  financial  information  relating  to
          Pioneer American,  NBT and BSB including annual reports for the fiscal
          years ended December 31, 1998 and December 31, 1999;  call report data
          from  1990 to  1999;  and the  Annual  Reports  on Form  10-K  and the
          Quarterly Reports on Form 10-Q for 1998 and 1999.

          Discussed  the past and current  operations,  financial  condition and
          prospects of NBT with its senior executives.

          Analyzed  the pro  forma  impact  of all of  NBT's  announced  banking
          mergers relative to earnings per share, capitalization,  and financial
          ratios.

          Reviewed the reported  prices and trading  activity for the NBT Common
          Stock and compared it to similar bank holding companies.

          Reviewed and  compared the  financial  terms,  to the extent  publicly
          available, with comparable transactions.

                                      11
<PAGE>


          Interviewed  NBT's  and  BSB's  senior  officers  relative  to the BSB
          merger.

          Reviewed the Pioneer American-NBT Merger Agreement and certain related
          documents.

          Reviewed NBT's  definitive  agreement with BSB and NBT's due diligence
          materials relative to BSB.

          Considered such other factors as were deemed appropriate.

     Danielson Associates did not obtain any independent  appraisal of assets or
liabilities of Pioneer  American,  NBT or BSB or their respective  subsidiaries.
Further,  Danielson  Associates  did not  independently  verify the  information
provided  by  Pioneer  American,  NBT  or  BSB  and  assumed  the  accuracy  and
completeness of all such information.

     In arriving at its  opinion,  Danielson  Associates  performed a variety of
financial  analyses.  Danielson  Associates  believes  that its analyses must be
considered as a whole and that  consideration of portions of such analyses could
create an incomplete view of Danielson Associates' opinion. The preparation of a
fairness opinion is a complex process involving subjective judgements and is not
necessarily susceptible to partial analysis or summary description.

     In its analyses, Danielson Associates made certain assumptions with respect
to industry  performance,  business and economic conditions,  and other matters,
many of which were beyond  Pioneer  American's or NBT's  control.  Any estimates
contained in Danielson  Associates  analyses are not  necessarily  indicative of
future results of value,  which may be significantly more or less favorable than
such  estimates.  Estimates  of the  value of  companies  do not  purport  to be
appraisals  or  necessarily  reflect  the  prices  at which  companies  or their
securities may actually be sold.

     The  following is a summary of selected  analyses  considered  by Danielson
Associates in connection with its opinion letter.

Pro Forma Merger Analyses

     Danielson  Associates  analyzed  the changes in the amount of earnings  and
book value  represented  by the receipt of about $62.5  million,  based on NBT's
April 19,  2000  stock  price,  for all of the  outstanding  shares  of  Pioneer
American Common Stock and options to purchase  Common Stock,  which will be paid
in NBT Common  Stock or options to  purchase  NBT  Common  Stock.  The  analysis
evaluated,  among other  things,  possible  dilution in earnings and capital per
share for NBT Common Stock.

Comparable Companies

     To determine  the "fair" value of the NBT common stock to be exchanged  for
the common stock of Pioneer American, NBT, by itself, and pro forma with BSB was
compared to eleven publicly-traded bank holding companies ("comparable banks" or
the "comparative group"). These comparable banks had assets in the $1 billion to
$3 billion  range,  no  extraordinary  characteristics  and were  located in New
Jersey, New York and Pennsylvania.

                   Summary and Description of Comparable Banks

<TABLE>
<CAPTION>
                                                          Assets*
                                                         (In mill.)             Headquarters
                                                         ----------             ------------

<S>                                                   <C>                     <C>
         Comparable Banks**
         Community Bank System                            $1,841                DeWitt, N.Y.
         Harleysville National                             1,636                Harleysville, Pa.
         Main Street                                       1,497                Reading, Pa.
         National Penn                                     2,242                Boyertown, Pa.
</TABLE>

                                       12
<PAGE>

<TABLE>
<CAPTION>
                                                          Assets*
                                                         (In mill.)             Headquarters
                                                         ----------             ------------
<S>                                                   <C>                     <C>
         Omega                                             1,053                State College, Pa.
         Premier National                                  1,596                Lagrangeville, N.Y.
         Sterling Financial                                1,059                Lancaster, Pa.
         TrustCo                                           2,364                Schenectady, N.Y.
         U.S.B.                                            1,646                Orangeburg, N.Y.
         United National                                   2,090                Bridgewater, N.J.
         Yardville                                         1,124                Mercerville, N.J.
</TABLE>

*    December 31, 1999.

**   Publicly-traded  with  assets  between  $1  billion  and $3  billion in New
     Jersey, New York and Pennsylvania.

Source:  SNL Securities LC, Charlottesville, Virginia.

         Danielson Associates compared NBT's:

               Stock price as of April 19, 2000 equal to 8.6 times  earnings and
               124% of book.

               Dividend yield based on trailing four quarters as of December 31,
               1999 and stock price as of April 19, 2000 of 6.58%.

               Equity and pro forma  equity as of December 31, 1999 of 9.08% and
               7.73% of assets, respectively.

               Nonperforming assets and pro forma nonperforming assets including
               loans 90 days past due as of December  31, 1999 equal to .35% and
               .48% of total assets, respectively.

               Return on average  assets and pro forma return on average  assets
               for 1999 of 1.38% and 1.12%, respectively.

               Return on average  equity and pro forma return on average  equity
               during the same period of 14.27% and 13.83%,  respectively,  with
               the medians for the comparable banks.

                         NBT - Comparable Banks Summary
<TABLE>
<CAPTION>
                                                                NBT &              Comparable Banks
                                            NBT                 BSB*               Medians
                                          -------               ------             ----------------
<S>                                     <C>                   <C>                 <C>
Income
  Net income/Avg. Assets                      1.38%               1.12%                    1.26%
  Net oper. income**/Avg. Assets              2.47                2.45                     2.06
  Return on average equity                   14.27               13.83                    15.22

Balance Sheet
  Equity/Assets                               9.08%               7.73%                    6.59%
  NPAs***/Assets                               .35                 .48                      .36

Stock Price
  Price/Earnings                               8.6X                 --                     12.3X
  Price/Book                                   124%                 --                      166%
  Dividend yield                              6.58%                 --                     4.21%
  Payout ratio                                  47%                 --                       48%
  Shares traded****                         24,307                  --                    9,139
</TABLE>

*    Excludes one-time merger charge taken by BSB in 1999.

**   Net interest income plus noninterest income less operating expense.

                                       13
<PAGE>


 *** Nonperforming assets including loans 90 days past due and still accruing.

**** Average daily volume in 2000 through April 19, 2000.

Source: SNL Securities LC, Charlottesville, Virginia.

     The comparable medians were:

          Stock price equal to 12.3 times earnings and 166% of book.

          Dividend yield of 4.21%.

          Equity of 6.59% of assets.

          36% of assets nonperforming.

          Return on average assets of 1.26%.

          Return on average equity of 15.22%.

Danielson  Associates  also  compared  other  income,  expense and balance sheet
information of such companies with similar information about NBT and BSB.

Comparable Transaction Analysis

     Danielson Associates compared the consideration to be paid in the merger to
the latest twelve months  earnings and equity  capital of Pioneer  American with
earnings and capital  multiples paid in  acquisitions of banks through April 19,
2000 in the Middle Atlantic and Northeast.  A specific  analysis of Pennsylvania
deals in the last two years was also included.  At the time Danielson Associates
made  its  analysis,  the  consideration  to be paid in the  merger  was 198% of
Pioneer American's December 31, 1999 book value and 15.3 times reported earnings
for 1999.  This compares to the median  multiples of 198% of book value and 16.5
times  earnings for  comparable  deals in the Middle  Atlantic and Northeast and
16.5 times earnings and 178% of book for comparable deals in Pennsylvania in the
last two years.

Discounted Future Earnings and Discounted Dividends Analysis

     Danielson   Associates   applied  present  value  calculations  to  Pioneer
American's  estimated future earnings and dividend stream under several specific
growth and earnings  scenarios.  This analysis  considered,  among other things,
scenarios  for Pioneer  American as an  independent  institution  and as part of
another  banking  organization.  The  projected  dividend  streams and  terminal
values, which were based on a range of earnings multiples,  were then discounted
to present value using discount  rates based on assumptions  regarding the rates
of return required by holders or prospective  buyers of Pioneer  American common
stock.

Other Analysis

     In  addition  to  performing  the  analyses  summarized  above,   Danielson
Associates also  considered the general market for bank mergers,  the historical
financial  performance of Pioneer American and NBT, the market positions of both
banks and the general economic conditions and prospects of those banks.

     No company or transaction  used in this composite  analysis is identical to
Pioneer  American  or  NBT.  Accordingly,  an  analyses  of the  results  of the
foregoing is not  mathematical;  rather it involves  complex  consideration  and
judgements concerning differences in financial and operating  characteristics of
the companies and other factors that could affect the public  trading  values of
the company or companies to which they are being compared.

                                       14
<PAGE>


     The summary  set forth above does not purport to be a complete  description
of the analyses and procedures  performed by Danielson  Associates in the course
of  arriving at its  opinions.  In payment  for its  services  as the  financial
advisor to Pioneer American, Danielson Associates is to be paid an estimated fee
of about $310,000.

     The full text of the opinion of Danielson  Associates dated as of April 20,
2000,  which sets forth  assumptions  made and matters  considered,  is attached
hereto as Appendix B of this joint proxy statement/prospectus.  Pioneer American
stockholders  are  urged  to  read  this  opinion  in  its  entirety.  Danielson
Associates'  opinion is  directed  only to the  consideration  to be received by
Pioneer  American   stockholders  in  the  Merger  and  does  not  constitute  a
recommendation  to any Pioneer  American  stockholder as to how such shareholder
should vote at the stockholders meeting.

                    PRICE RANGE OF COMMON STOCK AND DIVIDENDS

     NBT common  stock  trades on the Nasdaq  National  Market  under the symbol
"NBTB."  Following  the merger,  the shares of NBT common stock will continue to
trade on the Nasdaq National Market under that symbol.  Pioneer  American common
stock  trades  on  the  over-the-counter  market  under  the  symbol  "PAHC.OB."
Following the merger,  NBT will  deregister  the Pioneer  American  common stock
under the  Exchange  Act, and the common  stock of Pioneer  American  will cease
trading in the over-the-counter market.

     The  following  table has been  restated  to reflect  the payment by NBT on
December  15,  1999 of a 5%  stock  dividend  and  sets  forth  for the  periods
indicated (1) the range of high and low sales prices of the NBT common stock and
the Pioneer American common stock, and (2) the amount of cash dividends declared
per share by each company:

<TABLE>
<CAPTION>
                                                               NBT                           PIONEER AMERICAN
                                                              -----                         ------------------
                                                   SALES PRICES                         SALES PRICES
                                                   ------------                        --------------
                                                  HIGH        LOW       DIVIDENDS       HIGH        LOW      DIVIDENDS
                                                -------      -----     -----------   ---------   --------   ----------
<S>                                            <C>          <C>       <C>           <C>         <C>        <C>
1998
           First Quarter                          $19.05     $15.99        $ 0.117      $23.50     $21.38        $0.190
           Second Quarter                          23.48      18.37          0.154       25.25      22.50         0.190
           Third Quarter                           23.81      17.58          0.154       24.50      22.00         0.190
           Fourth Quarter                          24.29      19.72          0.162       23.50      22.00         0.200
1999
           First Quarter                          $23.33     $19.89        $ 0.162      $22.50     $19.00       $ 0.200
           Second Quarter                          21.19      19.05          0.162       28.00      19.13         0.200
           Third Quarter                           20.90      16.43          0.162       26.00      20.75         0.200
           Fourth Quarter                          17.98      14.63          0.170       30.00      23.50         0.200
2000
           First Quarter                          $16.50     $11.38         $0.170      $27.25     $19.75        $0.200
           Second Quarter (through
           May __, 2000)
</TABLE>

     The timing and amount of future  dividends will depend upon earnings,  cash
requirements, and financial condition of NBT and its subsidiaries and, following
the  merger of NBT and BSB,  the  earnings,  cash  requirements,  and  financial
condition of the surviving  corporation (and, prior to completion of the merger,
the earnings, cash requirements, and financial condition of Pioneer American and
its subsidiary insofar as Pioneer American dividends are concerned),  applicable
government  regulations,  and other factors deemed relevant by the NBT Board and
the board of directors of the surviving  corporation following the merger of NBT
and BSB (and by the Pioneer  American Board prior to completion of the merger of
NBT and Pioneer  American).  Various federal and state laws limit the ability of
affiliated  banks to pay  dividends  to NBT and  Pioneer  American.  The  merger
agreement with Pioneer American  restricts the cash dividends payable on Pioneer
American common stock pending completion of the merger.

                                       15
<PAGE>


     On May , 2000,  the most recent  practicable  date prior to the printing of
this  supplement,  the last  reported  sales price of NBT common stock was $ per
share. On May , 2000, the most recent  practicable date prior to the printing of
this supplement,  the last reported sales price of Pioneer American common stock
was $ per share. We urge  stockholders to obtain current market quotations prior
to making any decisions with respect to the merger.

     As of April 30,  2000,  there  were  4,676  holders of record of NBT common
stock and 1,434 holders of record of Pioneer American common stock.

                                     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  supplement  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 supplement and
registration  statement  in  reliance  upon the report of KPMG LLP,  independent
certified public  accountants,  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  supplement  and
registration  statement  in reliance  upon the report of  PricewaterhouseCoopers
LLP, independent certified public accountants,  incorporated herein by reference
and upon the authority of said firm as experts in accounting and auditing.

                       WHERE YOU CAN FIND MORE INFORMATION

     NBT and Pioneer American 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 NBT's SEC filings at the Nasdaq National Market,
1735 K Street, N.W.,  Washington,  D.C.  20006-1500,  and Pioneer American's SEC
filings  at  Nasdaq,  1735 K Street,  N.W.,  Washington,  D.C.  20006-1500.  Our
Internet   addresses   are    www.nbtbank.com    with   respect   to   NBT   and
www.pioneeramerican.com with respect to Pioneer American.

     NBT has filed a registration statement on Form S-4 to register with the SEC
the NBT common  stock to be issued to the  holders of  Pioneer  American  common
stock in the merger.  This supplement is a part of that  registration  statement
and  constitutes a prospectus  of NBT in addition to being a proxy  statement of
NBT and Pioneer  American for the NBT adjourned  annual  meeting and the Pioneer
American  adjourned  special meeting.  As allowed by SEC rules,  this supplement
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
supplement,  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  supplement,  except for
any information  superseded by information in this  supplement.  This supplement
incorporates  by reference the documents set forth below that we have previously
filed with the SEC. These  documents  contain  important  information  about the
companies, their finances and NBT common stock.

                                       16
<PAGE>

NBT BANCORP INC. SEC FILINGS

          Annual Report on Form 10-K for the year ended December 31, 1999; and

          Current  Reports on Form 8-K, filed with the SEC on February 22, 2000,
          March 3, 2000, March 31, 2000 and April 28, 2000.

     On March 31, 2000, NBT filed a Current Report on Form 8-K with the SEC. The
report  contains  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,  which have been restated to include the effects of the
Lake  Ariel  Bancorp,  Inc.merger,  which  was  accounted  for as a  pooling  of
interests.

PIONEER AMERICAN HOLDING COMPANY CORP. SEC FILINGS

          Annual Report on Form 10-K for the year ended December 31, 1999; and

          Current Report on Form 8-K, filed with the SEC on January 4, 2000.

     We incorporate by reference  additional documents that we file with the SEC
pursuant to Sections  13(a),  13(c), 14 or 15(d) of the Exchange Act between the
date of this supplement and the effective time of the merger.

     NBT has supplied all information  contained or incorporated by reference in
this  supplement  relating to NBT,  and Pioneer  American  has supplied all such
information relating to Pioneer American.

     If you are a  stockholder,  we may  have  sent  you  some of the  documents
incorporated by reference, but you can obtain any of them through us or the SEC.
You can obtain  documents  incorporated  by  reference  from us without  charge,
excluding all exhibits unless we have specifically  incorporated by reference an
exhibit in this supplement.  Stockholders  may obtain documents  incorporated by
reference in this  supplement by requesting them in writing or by telephone from
the appropriate party at the following address:

     NBT Bancorp Inc.                     Pioneer American Holding Company Corp.
     52 South Broad Street                41 North Main Street
     Norwich, New York 13815              Carbondale, PA 18407
     Attention: Michael J. Chewens, CPA   Attention: Patricia A. Cobb, Esq.
     Tel: (607) 337-6520                  Tel: (570) 282-8045

     If you would like to request  documents  from us,  please do so by June 13,
2000 to receive them prior to the  reconvened  NBT annual meeting and reconvened
Pioneer American special meeting.

     YOU  SHOULD  RELY ONLY ON THE  INFORMATION  CONTAINED  OR  INCORPORATED  BY
REFERENCE  IN  THIS  SUPPLEMENT  TO VOTE ON THE  NBT  PROPOSAL  AND THE  PIONEER
AMERICAN PROPOSAL. WE HAVE NOT AUTHORIZED ANYONE TO PROVIDE YOU WITH INFORMATION
THAT IS DIFFERENT FROM WHAT IS CONTAINED IN THIS SUPPLEMENT.  THIS SUPPLEMENT IS
DATED MAY , 2000. YOU SHOULD NOT ASSUME THAT THE  INFORMATION  CONTAINED IN THIS
SUPPLEMENT  IS  ACCURATE  AS OF ANY DATE OTHER THAN SUCH DATE,  AND  NEITHER THE
MAILING OF THIS  SUPPLEMENT  TO  STOCKHOLDERS  NOR THE ISSUANCE OF SHARES OF NBT
COMMON STOCK IN THE MERGER SHALL CREATE ANY IMPLICATION TO THE CONTRARY.

                UNAUDITED PRO FORMA COMBINED FINANCIAL STATEMENTS

     The following  unaudited  pro forma  combined  balance  sheet  presents the
financial position of NBT, Pioneer American and BSB Bancorp, Inc. as of December
31, 1999,  assuming that each merger had occurred as of December 31, 1999, after
giving  effect to certain pro forma  adjustments  described in the  accompanying
notes. The following  unaudited pro forma combined  statements of income for the
years ended  December  31, 1999,  1998 and 1997 present the combined  historical
results of  operations  of NBT,  Pioneer  American and BSB as if each merger had
been  consummated  as of the first day of the period  presented.  The  financial
information  for NBT has been restated to include the effects of the merger with
Lake Ariel  Bancorp,  Inc.,  which was  consummated on February 17, 2000 and has
been

                                       17
<PAGE>


accounted for as a pooling of interests. Pro forma earnings per common share are
based on the exchange ratio of 1.805 with respect to the Pioneer American merger
and 2.0 with respect to the merger with BSB.  The fiscal  years of NBT,  Pioneer
American and BSB end December 31. The unaudited pro forma combined balance sheet
reflects  estimated  non-recurring  charges that will be incurred in  connection
with the mergers.

     The unaudited pro forma combined financial  statements were prepared giving
effect to each merger on the pooling of interests  accounting method. Under this
method of accounting,  the recorded assets,  liabilities,  stockholders' equity,
income and expense of NBT,  Pioneer  American and BSB 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 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  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,  Pioneer
American and BSB and the supplemental  consolidated  financial statements of NBT
and accompanying  notes,  which have been restated to include the effects of the
Lake  Ariel  merger.  All of these  financial  statements  are  incorporated  by
reference  into this  supplement.  The  unaudited pro forma  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  consummated  on
December 31, 1999 or at the  beginning of the periods or that may be attained in
the future.

                                       18
<PAGE>

<TABLE>
<CAPTION>

                                                           UNAUDITED PRO FORMA CONDENSED
                                                              COMBINED BALANCED SHEET
                                                                AT DECEMBER 31, 1999


                                                                               PIONEER                              NBT
                                                                               AMERICAN                             PIONEER
                                                                                HOLDING                             AMERICAN
                                                                NBT             COMPANY             PRO FORMA       COMBINED
                                                            BANCORP INC.          CORP.            ADJUSTMENTS      PRO FORMA
                                                            ------------      ----------           -----------      ---------
<S>                                                        <C>                <C>                 <C>              <C>

(in thousands)

ASSETS
Cash and cash equivalents                                  $     64,431        $  15,198          $       --     $     79,629
Securities available for sale, at fair value                    520,440          112,134                  --          632,574
Securities held to maturity (fair value-NBT Bancorp
  Inc. $75,155, Pioneer American Holding Company
  Corp.$35,499 and BSB Bancorp, Inc. $14,588)                    78,213           36,612                  --          114,825
Loans:                                                        1,222,654          244,213                  --        1,466,867
Less: Allowance for loan losses                                  16,654            3,057                  --           19,711
                                                             ----------        ---------                            ---------
         Net Loans                                            1,206,000          241,156                  --        1,447,156
Premises and equipment, net                                      40,830            6,267                  --           47,097
Other assets                                                     51,518            7,408               3,300(6)        62,226
                                                             ----------        ---------                            ---------
TOTAL ASSETS                                              $   1,961,432        $ 418,775          $    3,300     $  2,383,507
                                                             ==========        =========                            =========

LIABILITIES AND STOCKHOLDERS' EQUITY
Deposits:
   Demand (noninterest bearing)                                $223,143        $  44,752          $      --      $    267,895
   Savings, NOW, and money market                               487,746          117,588                 --           605,334
   Time                                                         766,729          137,133                 --           903,862
                                                             ----------        ---------                            ---------
        Total deposits                                        1,477,618          299,473                 --         1,777,091
Short-term borrowings                                           137,567            4,700                 --           142,267
Long-term debt                                                  172,575           79,395                 --           251,970
Other liabilities                                                13,798            3,609             12,300(6)         29,707
Mandatory redemmable preferred securities of subsidiary              --              --                  --                --
                                                             ----------        ---------           --------         ---------
        Total liabilities                                     1,801,558          387,177             12,300         2,201,035
                                                             ----------        ---------           --------         ---------

Commitments and contingencies

Stockholders' equity:
   Preferred stock                                                   --              --                  --                --
   Common stock                                                  18,489           2,935               2,235(2)         23,659
   Capital surplus                                              148,242          11,962              (3,965)(2)       156,239
   Retained earnings                                             23,060          21,889              (9,000)(6)        35,949
   Accumulated other comprehensive income (loss)                (18,252)         (3,458)                 --           (21,710)
   Common stock in treasury at cost                             (11,665)         (1,730)              1,730(2)        (11,665)
        Total stockholders' equity                              159,874          31,598              (9,000)          182,472
TOTAL LIABILITIES AND
   STOCKHOLDERS' EQUITY                                   $   1,961,432        $418,775          $    3,300      $  2,383,507
</TABLE>

<PAGE>

<TABLE>
<CAPTION>


                                                                                                  NBT
                                                                                                PIONEER
                                                                                                AMERICAN
                                                                                                  BSB
                                                             BSB BANCORP,        PRO FORMA      COMBINED
                                                                  INC.           ADJUSTMENTS    PRO FORMA
                                                             ------------       ------------    ---------
<S>                                                         <C>                 <C>             <C>

(in thousands)

ASSETS
Cash and cash equivalents                                   $    70,065        $      --     $   149,694
Securities available for sale, at fair value                    387,251               --       1,019,825
Securities held to maturity (fair value-NBT Bancorp
  Inc. $75,155, Pioneer American Holding Company
  Corp. $35,499 and BSB Bancorp, Inc. $14,588)                   14,472               --         129,297
Loans:                                                        1,724,973               --       3,191,840
Less: Allowance for loan losses                                  29,134               --          48,845
                                                              ---------                        ---------
         Net Loans                                            1,695,839               --       3,142,995
Premises and equipment, net                                      15,988               --          63,085
Other assets                                                     57,333            4,500(6)      124,059
                                                              ---------                        ---------
TOTAL ASSETS                                                $ 2,240,948        $   4,500     $ 4,628,955
                                                              =========           ======       =========

LIABILITIES AND STOCKHOLDERS' EQUITY
Deposits:
   Demand (noninterest bearing)                             $   141,907        $      --        $409,802
   Savings, NOW, and money market                               647,987               --       1,253,321
   Time                                                       1,111,310               --       2,015,172
                                                              ---------                        ---------
        Total deposits                                        1,901,204               --       3,678,295
Short-term borrowings                                           119,048               --         261,315
Long-term debt                                                   22,997               --         274,967
Other liabilities                                                13,206           16,500(6)       59,413
Mandatory redemmable preferred securities of subsidiary          30,000               --          30,000
                                                              ---------           ------       ---------
        Total liabilities                                     2,086,455           16,500       4,303,990
                                                              ---------           ------       ---------

Commitments and contingencies

Stockholders' equity:
   Preferred stock                                                   --              --               --
   Common stock                                                     114          20,337(5)        44,110
   Capital surplus                                               37,287         (33,783)(5)      159,743
   Retained earnings                                            140,295         (12,000)(6)      164,244
   Accumulated other comprehensive income (loss)                 (9,757)             --          (31,467)
   Common stock in treasury at cost                             (13,446)          13,446(5)      (11,665)
        Total stockholders' equity                              154,493          (12,000)        324,965
                                                              ---------          -------       ---------
TOTAL LIABILITIES AND
   STOCKHOLDERS' EQUITY                                     $ 2,240,948        $   4,500     $ 4,628,955
                                                            ===========        =========     ===========
</TABLE>


See accompanying notes to the unaudited pro forma combined financial statements.


                                       19
<PAGE>

           UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF INCOME

<TABLE>
<CAPTION>
                                                                         FOR THE YEAR ENDED DECEMBER 31, 1999

                                                                               PIONEER                             NBT
                                                                               AMERICAN                          PIONEER
                                                                  NBT          HOLDING                           AMERICAN
                                                                BANCORP        COMPANY          PRO FORMA        COMBINED
                                                                  INC.           CORP.          ADJUSTMENTS     PRO FORMA
                                                              -----------     ----------      --------------    -----------
<S>                                                         <C>              <C>             <C>               <C>

Consolidated Statement of Income:
(in thousands, except per share data)

Interest and fee income:
     Loans and loans held for sale                             $  96,235      $   19,661         $     --       $  115,896
     Securities - taxable                                         34,956           8,223               --           43,179
     Securities - tax-exempt                                       3,210           1,268               --            4,478
     Other                                                           988             237               --            1,225
                                                               ---------      ----------         --------       ----------
         Total interest and fee income                           135,389          29,389               --          164,778
                                                               ---------      ----------         --------       ----------

Interest expense:
     Deposits                                                     46,067          10,519               --           56,586
     Borrowings                                                   14,515           4,379               --           18,894
                                                               ---------      ----------         --------       ----------
         Total interest expense                                   60,582          14,898                            75,480
                                                               ---------      ----------         --------       ----------
     Net interest income                                          74,807          14,491               --           89,298
     Provision for loan losses                                     5,070             370               --            5,440
                                                               ---------      ----------         --------       ----------
     Net interest income after provision for loan losses          69,737          14,121               --           83,858
                                                               ---------      ----------         --------       ----------

Noninterest income:
     Trust                                                         3,305              --               --            3,305
     Service charges on deposit accounts                           6,303           1,635               --            7,938
     Net securities gains (losses)                                 1,716              88               --            1,804
     Other                                                         5,097           1,108               --            6,205
                                                               ---------      ----------         --------       ----------
         Total noninterest income                                 16,421           2,831               --           19,252
                                                               ---------      ----------         --------       ----------

Noninterest expense:
     Salaries and employee benefits                               25,213           5,291               --           30,504
     Office supplies and postage                                   2,436             534               --            2,970
     Occupancy                                                     4,317           1,062               --            5,379
     Equipment                                                     4,230             990               --            5,220
     Professional fees and outside services                        3,325           1,005               --            4,330
     Data processing and communications                            4,091             437               --            4,528
     Amortization of intangible assets                             1,278              39               --            1,317

     Acquisition charges                                              --              --               --               --
     Other operating                                               6,610           2,024               --            8,634
                                                               ---------      ----------         --------       ----------
         Total noninterest expense                                51,500          11,382               --           62,882
                                                               ---------      ----------         --------       ----------
     Income before income taxes                                   34,658           5,570               --           40,228
     Income taxes                                                 12,483           1,488               --           13,971
                                                               ---------      ----------         --------       ----------
         Net income                                             $ 22,175      $    4,082         $     --         $ 26,257
                                                               =========      ==========         ========       ==========

Weighted Average Shares Outstanding:
     Basic                                                        17,851           2,902               --           23,089
     Diluted                                                      18,095           2,929               --           23,382

Earnings per share:
     Basic                                                      $   1.24      $     1.41               --         $   1.14
     Diluted                                                    $   1.23      $     1.39               --         $   1.12

</TABLE>








<PAGE>


<TABLE>
<CAPTION>
                                                                                               NBT
                                                                                            PIONEER
                                                                                            AMERICAN
                                                              BSB                              BSB
                                                            BANCORP,         PRO FORMA      COMBINED
                                                             INC,          ADJUSTMENTS     PRO FORMA
                                                           ----------     --------------  -----------
<S>                                                        <C>             <C>              <C>

Consolidated Statement of Income:
(in thousands, except per share data)

Interest and fee income:
     Loans and loans held for sale                         $ 151,001        $     --       $ 266,897
     Securities - taxable                                     24,113              --          67,292
     Securities - tax-exempt                                     925              --           5,403
     Other                                                       682                           1,907
                                                           ---------        --------       ---------
         Total interest and fee income                       176,721              --         341,499
                                                           ---------        --------       ---------

Interest expense:
     Deposits                                                 75,542              --         132,128
     Borrowings                                               14,034              --          32,928
                                                           ---------        --------       ---------
         Total interest expense                               89,576              --         165,056
                                                           ---------        --------       ---------
     Net interest income                                      87,145              --         176,443
     Provision for loan losses                                19,137              --           24,577
                                                           ---------        --------       ---------
     Net interest income after provision for loan losses      68,008              --         151,866
                                                           ---------        --------       ---------

Noninterest income:
     Trust                                                     1,104              --           4,409
     Service charges on deposit accounts                       4,382              --          12,320
     Net securities gains (losses)                              (231)             --           1,573
     Other                                                     7,116              --          13,321
                                                           ---------        --------       ---------
         Total noninterest income                             12,371              --          31,623
                                                           ---------        --------       ---------

Noninterest expense:
     Salaries and employee benefits                           20,386              --          50,890
     Office supplies and postage                               1,684              --           4,654
     Occupancy                                                 2,874              --           8,253
     Equipment                                                 1,733              --           6,953
     Professional fees and outside services                    6,001              --          10,331
     Data processing and communications                        1,930              --           6,458
     Amortization of intangible assets                           386              --           1,703

     Acquisition charges                                       5,408              --           5,408
     Other operating                                          10,261              --          18,895
                                                           ---------        --------       ---------
         Total noninterest expense                            50,663              --         113,545
                                                           ---------        --------       ---------
     Income before income taxes                               29,716              --          69,944
     Income taxes                                             11,491              --          25,462
                                                           ---------        --------       ---------
         Net income                                        $  18,225        $     --        $ 44,482
                                                           =========        ========       =========

Weighted Average Shares Outstanding:
     Basic                                                    10,138                          43,365
     Diluted                                                  10,312                          44,006

Earnings per share:
     Basic                                                 $    1.80                         $  1.03
     Diluted                                               $    1.77                         $  1.01
                                                                  --
</TABLE>






See accompanying notes to the unaudited pro forma combined financial statements.

                                       20
<PAGE>


           UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF INCOME

<TABLE>
<CAPTION>
                                                                                       FOR THE YEAR ENDED DECEMBER 31, 1998

                                                                               PIONEER                           NBT
                                                                              AMERICAN                         PIONEER
                                                                               HOLDING                         AMERICAN
                                                                NBT            COMPANY       PRO FORMA         COMBINED
                                                            BANCORP INC.        CORP.        ADJUSTMENTS       PRO FORMA
                                                           --------------    ------------   -------------    -------------
<S>                                                       <C>               <C>            <C>              <C>
Consolidated Statement of Income:
(in thousands, except per share data)

Interest and fee income:
     Loans and loans held for sale                          $   89,399        $  19,093       $      --       $   108,492
     Securities - taxable                                       37,590            7,615              --            45,205
     Securities - tax-exempt                                     2,780            1,114              --             3,894
     Other                                                         531              480              --             1,011
                                                              ---------        --------       ---------       -----------
         Total interest and fee income                         130,300           28,302              --           158,602
                                                              ---------        --------       ---------       -----------

Interest expense:
     Deposits                                                   48,058           10,840              --            58,898
     Borrowings                                                 12,359            3,479              --            15,838
                                                              ---------        --------       ---------       -----------
         Total interest expense                                 60,417           14,319              --            74,736
                                                              ---------        --------       ---------       -----------
     Net interest income                                        69,883           13,983              --            83,866
     Provision for loan losses                                   5,729              420              --             6,149
                                                              ---------        --------       ---------       -----------
     Net interest income after provision for loan losses        64,154           13,563              --            77,717
                                                              ---------        --------       ---------       -----------

Noninterest income:
      Trust                                                      3,115               --              --             3,115
      Service charges on deposit accounts                        5,325            1,404              --             6,729
      Net securities gains (losses)                              1,056              511              --             1,567
      Other                                                      5,417            1,046              --             6,463
                                                              ---------        --------       ---------       -----------
          Total noninterest income                              14,913            2,961              --            17,874
                                                              ---------        --------       ---------       -----------

Noninterest expense:
      Salaries and employee benefits                            24,215            5,071              --            29,286
      Office supplies and postage                                2,523              506              --             3,029
      Occupancy                                                  4,132            1,027              --             5,159
      Equipment                                                  3,599              773              --             4,372
      Professional fees and outside services                     3,375            1,027              --             4,402
      Data processing and communications                         3,796              483              --             4,279
      Amortization of intangible assets                          1,275               39              --             1,314

      Other operating                                            7,665            2,041              --             9,706
                                                              --------         --------       ---------       -----------
          Total noninterest expense                             50,580           10,967              --            61,547
                                                              --------         --------       ---------       -----------
      Income before income taxes                                28,487            5,557              --            34,044
      Income taxes                                               5,614            1,535              --             7,149
                                                              --------         --------       ---------       -----------
          Net income                                          $ 22,873        $   4,022      $       --          $ 26,895
                                                              ========         ========       =========       ===========

Weighted Average Shares Outstanding:
      Basic                                                     17,976            2,894              --            23,199
      Diluted                                                   18,361            2,953              --            23,691

Earnings per share:
      Basic                                                  $    1.27        $    1.39      $       --      $       1.16
      Diluted                                                $    1.25        $    1.36      $       --      $       1.14
</TABLE>

                           See  accompanying  notes to the  unaudited  pro forma
combined financial statements.







<TABLE>
<CAPTION>
                                                                                                  NBT
                                                                                                PIONEER
                                                                                               AMERICAN
                                                               BSB                                BSB
                                                             BANCORP,          PRO FORMA       COMBINED
                                                               INC.            ADJUSTMENTS     PRO FORMA
                                                           -----------        -------------   ----------
<S>                                                       <C>                <C>              <C>
Consolidated Statement of Income:
(in thousands, except per share data)

Interest and fee income:
     Loans and loans held for sale                          $ 139,374         $    --        $247,866
     Securities - taxable                                      25,220              --          70,425
     Securities - tax-exempt                                      706              --           4,600
     Other                                                        866              --           1,877
                                                              -------           -----          ------
         Total interest and fee income                        166,166              --         324,768
                                                              -------           -----          ------

Interest expense:
     Deposits                                                  72,387              --         131,285
     Borrowings                                                12,399              --          28,237
                                                               ------              --          ------
         Total interest expense                                84,786              --         159,522
                                                               ------              --         -------
     Net interest income                                       81,380              --         165,246
     Provision for loan losses                                 12,931              --          19,080
                                                               ------              --          ------
     Net interest income after provision for loan losses       68,449              --         146,166
                                                               ------              --         -------

Noninterest income:
      Trust                                                       994              --           4,109
      Service charges on deposit accounts                       3,714              --          10,443
      Net securities gains (losses)                              (851)             --             716
      Other                                                     4,738              --          11,201
                                                               -----            -----          ------
          Total noninterest income                              8,595              --          26,469
                                                               ------          ------          ------

Noninterest expense:
      Salaries and employee benefits                           19,528              --          48,814
      Office supplies and postage                               1,998              --           5,027
      Occupancy                                                 2,911              --           8,070
      Equipment                                                 1,466              --           5,838
      Professional fees and outside services                    4,086              --           8,488
      Data processing and communications                        2,027              --           6,306
      Amortization of intangible assets                           386              --           1,700

      Other operating                                           9,581                          19,287
                                                                -----                          ------
          Total noninterest expense                            41,983                         103,530
                                                               ------                         -------
      Income before income taxes                               35,061              --          69,105
      Income taxes                                             13,542                          20,691
                                                               ------                          ------
          Net income                                         $ 21,519          $   --        $ 48,414
                                                               ======                          ======

Weighted Average Shares Outstanding:
      Basic                                                    10,006              --          43,211
      Diluted                                                  10,365              --          44,421

Earnings per share:
      Basic                                                  $   2.15          $   --         $  1.12
      Diluted                                                $   2.08          $   --         $  1.09

</TABLE>

                                       21
<PAGE>

           UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF INCOME

<TABLE>
<CAPTION>
                                                                           FOR THE YEAR ENDED DECEMBER 31, 1997

                                                                              PIONEER                              NBT
                                                                             AMERICAN                            PIONEER
                                                               NBT            HOLDING                           AMERICAN
                                                             BANCORP          COMPANY            PRO FORMA      COMBINED
                                                               INC.             CORP.           ADJUSTMENTS     PRO FORMA
                                                           ----------      -----------       ---------------- ------------
<S>                                                       <C>             <C>              <C>               <C>
Consolidated Statement of Income:
(in thousands, except per share data)

Interest and fee income:
     Loans and loans held for sale                          $  81,688       $   18,101          $     --       $   99,789
     Securities - taxable                                      35,779            7,063                --           42,842
     Securities - tax-exempt                                    2,757            1,023                --            3,780
     Other                                                        607              320                --              927
                                                             --------           ------            ------          -------
         Total interest and fee income                        120,831           26,507                --          147,338
                                                             --------           ------            ------          -------

Interest expense:
     Deposits                                                  45,629           11,337                --           56,966
     Borrowings                                                10,418            1,508                --           11,926
                                                             --------           ------            ------          -------
         Total interest expense                                56,047           12,845                --           68,892
                                                             --------           ------            ------          -------
     Net interest income                                       64,784           13,662                --           78,446
     Provision for loan losses                                  4,285              535                --            4,820
                                                             --------           ------            ------          -------
     Net interest income after provision for loan losses       60,499           13,127                --           73,626
                                                             --------           ------            ------          -------

Noninterest income:
     Trust                                                      2,675               --                --            2,675
     Service charges on deposit accounts                        4,942            1,397                --            6,339
     Net securities gains (losses)                               (123)             157                --               34
     Other                                                      3,973              907                --            4,880
                                                             --------           ------            ------          -------
         Total noninterest income                              11,467            2,461                --           13,928
                                                             --------           ------            ------          -------

Noninterest expense:
     Salaries and employee benefits                            22,111            5,040                --           27,151
     Office supplies and postage                                2,250              507                --            2,757
     Occupancy                                                  3,754            1,026                --            4,780
     Equipment                                                  2,632              685                --            3,317
     Professional fees and outside services                     2,485              900                --            3,385
     Data processing and communications                         2,966              456                --            3,422
     Amortization of intangible assets                          1,505               39                --            1,544

     Other operating                                            6,677            1,427                --            8,104
                                                             --------           ------            ------          -------
         Total noninterest expense                             44,380           10,080                --           54,460
                                                             --------           ------            ------          -------
     Income before income taxes                                27,586            5,508                --           33,094
     Income taxes                                               9,406            1,500                --           10,906
                                                             --------           ------            ------          -------
         Net income                                          $ 18,180         $  4,008           $               $ 22,188
                                                             ========           ======            ======          =======

Weighted Average Shares Outstanding:
     Basic                                                     17,095            2,850               --            22,239
     Diluted                                                   17,393            2,939               --            22,698

Earnings per share:
     Basic                                                   $   1.06         $   1.41           $   --      $       1.00
     Diluted                                                 $   1.05         $   1.36           $   --      $       0.98

</TABLE>


See accompanying notes to the unaudited pro forma combined financial statements.








<PAGE>


<TABLE>
<CAPTION>


                                                                                                  NBT
                                                                                                PIONEER
                                                                                               AMERICAN
                                                              BSB                                 BSB
                                                            BANCORP,           PRO FORMA       COMBINED
                                                              INC.             ADJUSTMENTS     PRO FORMA
                                                          ------------       --------------   ----------
<S>                                                       <C>                 <C>               <C>

Consolidated Statement of Income:
(in thousands, except per share data)

Interest and fee income:
     Loans and loans held for sale                           $120,750         $    --        $220,539
     Securities - taxable                                      19,373              --          62,215
     Securities - tax-exempt                                    1,025              --           4,805
     Other                                                        200              --           1,127
                                                              -------         -------        --------
         Total interest and fee income                        141,348              --         288,686
                                                              -------         -------        --------

Interest expense:
     Deposits                                                  60,180              --         117,146
     Borrowings                                                11,272              --          23,198
                                                              -------         -------        --------
         Total interest expense                                71,452              --         140,344
                                                              -------         -------        --------
     Net interest income                                       69,896              --         148,342
     Provision for loan losses                                 10,814              --          15,634
                                                              -------         -------        --------
     Net interest income after provision for loan losses       59,082              --         132,708
                                                              -------         -------        --------

Noninterest income:
     Trust                                                        709              --           3,384
     Service charges on deposit accounts                        3,297              --           9,636
     Net securities gains (losses)                                380              --             414
     Other                                                      3,762              --           8,642
                                                              -------         -------        --------
         Total noninterest income                               8,148              --          22,076
                                                              -------         -------        --------

Noninterest expense:
     Salaries and employee benefits                            17,121              --          44,272
     Office supplies and postage                                1,886              --           4,643
     Occupancy                                                  2,547              --           7,327
     Equipment                                                  1,378              --           4,695
     Professional fees and outside services                     2,716              --           6,101
     Data processing and communications                         1,358              --           4,780
     Amortization of intangible assets                            386              --           1,930

     Other operating                                            9,548                          17,652
                                                              -------                        --------
         Total noninterest expense                             36,940                          91,400
                                                              -------                        - ------
     Income before income taxes                                30,290              --          63,384
     Income taxes                                              11,641
                                                              -------
         Net income                                          $ 18,649        $     --       $  40,837
                                                              =======         =======         =======

Weighted Average Shares Outstanding:
     Basic                                                     9,905               --          42,049
     Diluted                                                  10,258               --          43,214

Earnings per share:
     Basic                                                   $  1.88         $     --        $   0.97
     Diluted                                                 $  1.82         $     --        $   0.94

</TABLE>


                                       22

<PAGE>


           NOTES TO UNAUDITED PRO FORMA COMBINED FINANCIAL STATEMENTS

(1) Pro forma earnings per common share (EPS) have been calculated  based on the
weighted  average number of shares of NBT plus additional  shares of NBT assumed
to be issued in the mergers in exchange  for the  weighted  average  outstanding
shares of  Pioneer  American  and BSB for each  applicable  period  based on the
exchange ratios of 1.805 and 2.0, respectively.

(2) Pro forma entry to issue 1.805  shares of NBT Bancorp  Inc.  Common Stock in
exchange for each share of Pioneer American Holding Company Corp.  Common Stock.
The stated value of NBT Bancorp Inc.  Common Stock to be issued is determined as
follows:

<TABLE>
<S>                                                                  <C>                  <C>

NBT Bancorp Inc. common shares issued at December 31, 1999                                18,488,347
Pioneer American Holding Company Corp. common shares issued, after
  retirement of treasury stock
  (2,864,307 common shares times conversion
  ratio of 1.805)                                                                          5,170,074
Combined pro forma total common share issued                                              23,658,421
Stated value per common share                                                            $      1.00
Combined pro forma total stated value                                                    $23,658,421

Actual stated value of common stock at December 31, 1999:

NBT Bancorp Inc.                                                  $18,488,347
Pioneer American Holding Company Corp.
 (after retirement of treasury shares)                              2,864,307           $21,352,654
Required increase in stated value                                                       $ 2,305,767

Entry to conform to stated value of common stock:
Surplus                                                           $ 2,305,767
Common stock                                                                            $ 2,305,767

Pro forma entry to retire treasury stock held by Pioneer
 (approximately 71,060 shares having a par value of $1.00
 per share)
Common Stock                                                      $    71,060
Surplus                                                           $ 1,658,739
Treasury Stock                                                                          $ 1,729,799

Summary of pro forma entries above

Surplus                                                           $ 3,964,506
Common stock                                                                            $ 2,234,707
Treasury Stock                                                                          $ 1,729,799
</TABLE>

     (3) Authorized,  issued and outstanding  share information is as follows at
December 31, 1999:

<TABLE>
<CAPTION>
                                                 NBT                 PIONEER             NBT/PIONEER PRO FORMA
                                              -----------         --------------      -------------------------
<S>                                          <C>                <C>                 <C>
Preferred
   Authorized                                   2,500,000                    --                       2,500,000
   Issued and Outstanding                              --                    --                              --
Common
   Stated Value                                     $1.00                 $1.00                           $1.00
   Authorized                                  15,000,000(A)         25,000,000                      15,000,000(A)
   Issued                                      18,488,347             2,935,367                      23,658,421
   Outstanding                                 17,949,411             2,864,307                      23,119,485
</TABLE>

                                       23
<PAGE>


     (A) On February 17,  2000,  stockholders  of NBT Bancorp  Inc.  approved an
amendment  to  its  Certificate  of  Incorporation   increasing  the  number  of
authorized  common  shares  from 15 million to 30 million and  changing  the par
value of the NBT capital stock from no par value,  $1.00 stated  value,  to $.01
par value per share..

(4)  Pro  forma  entry  to  retire  treasury  stock  held by BSB  Bancorp,  Inc.
     (approximately 1,173,669 shares having a par value of $.01 per share)

<TABLE>
<S>                                                            <C>
         Common stock                                             $    11,737
         Surplus                                                  $13,434,263
         Treasury stock                                           $13,446,000
</TABLE>

(5)  Pro forma entry to issue 2.0 shares of NBT  Bancorp  Inc.  common  stock in
     exchange for each share of BSB Bancorp, Inc. common stock. The stated value
     of NBT  Bancorp  Inc.  common  stock to be issued at  December  31, 1999 is
     determined as follows:

<TABLE>
<S>                                                                           <C>               <C>
         NBT Bancorp Inc. / Pioneer combined pro forma common shares issued                         23,658,421
         BSB Bancorp, Inc. common shares issued, after
                  retirement of treasury stock
                  (10,225,322 common shares times conversion
                   ratio of 2.0)                                                                    20,450,644
                                                                                                   -----------
         Combined pro forma total common shares issued                                              44,109,065
         Stated value per common share                                                            $       1.00
                                                                                                   -----------
         Combined pro forma total stated value                                                    $ 44,109,065

         Actual stated value of common stock at December 31, 1999:

         NBT Bancorp Inc. / Pioneer combined pro forma                            $23,658,421
         BSB Bancorp, Inc. (after retirement of treasury stock )                      102,253     $ 23,760,674
                                                                                  --------------  ------------
         Required increase in stated value                                                        $ 20,348,391
                                                                                                  ============

         Entry to conform to stated value of common stock:

         Surplus                                                                 $ 20,348,391
         Common stock                                                                             $ 20,348,391
</TABLE>

                                       24
<PAGE>



Summary of pro forma entries from notes (4) and (5) above

<TABLE>
<S>                                                                             <C>             <C>
         Surplus                                                                  $33,782,654
         Common stock                                                                             $ 20,336,654
         Treasury stock                                                                           $ 13,446,000
</TABLE>

(6) The  unaudited  pro forma  combined  balance  sheet at  December  31,  1999,
reflects  anticipated  non-recurring  merger and integration  costs for the Lake
Ariel, Pioneer American and BSB mergers.  Costs related to the Lake Ariel merger
are  estimated to be in the range of $6.7 million to $7.7 million  ($4.7 million
to $5.7 million  after taxes) and 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 systems integration costs, and
employee and contract termination costs. Anticipated merger and integration cost
estimates  are not included in the unaudited  pro forma  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 entries to record the anticipated  merger and integration  costs on the
unaudited pro forma combined balance sheet are:

<TABLE>
<S>                                       <C>               <C>
Lake Ariel
Current Tax Receivable                    $2,000,000
Retained Earnings                         $5,200,000
  Other Liabilities                                         $ 7,200,000

Pioneer American
Current Tax Receivable                    $1,300,000
Retained Earnings                         $3,800,000
  Other Liabilities                                         $ 5,100,000

Summary of pro forma entries above
Current Tax Receivable                    $3,300,000
Retained Earnings                         $9,000,000
  Other Liabilities                                         $12,300,000

BSB
Current Tax Receivable                    $4,500,000
Retained Earnings                        $12,000,000
  Other Liabilities                                         $16,500,000
</TABLE>


                                       25
<PAGE>



            CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

     NBT  and  Pioneer   American  have  used  and   incorporated  by  reference
"forward-looking  statements"  in this  supplement.  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.  NBT and Pioneer American have used these statements to describe our
expectations and estimates in various sections of this supplement, including:

     Presidents' Letter to the Stockholders;

     Proposed Merger Between NBT and BSB;

     Revised  Fairness  Opinions  by  Financial  Advisors  --  Opinion  of NBT's
     Financial Advisor;

     Revised  Fairness  Opinions  by  Financial  Advisors  -- Opinion of Pioneer
     American's Financial Advisor; and

     Unaudited Pro Forma Combined Financial Statements.

     Factors that might cause such differences  include, but are not limited to:
the timing of closing the proposed mergers being delayed;  competitive pressures
among financial  institutions  increasing  significantly;  economic  conditions,
either  nationally  or locally in areas in which NBT,  Pioneer  American and BSB
conduct their  operations,  being less  favorable  than  expected;  the cost and
effort  required to integrate  aspects of the operations of the companies  being
more difficult than  expected;  expected cost savings from the proposed  mergers
not being fully realized or realized within the expected time frame; legislation
or regulatory changes which adversely affect the ability of the combined company
to conduct its current and future  operations;  and the impact of the transition
to the year 2000 on the operations of NBT, Pioneer American, BSB or the combined
company.  NBT and Pioneer  American  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 supplement to reflect future events
or  developments.  NBT's actual results could differ  materially  from those set
forth in the forward-looking  statements because of many reasons,  including the
risk factors listed above. This list may not be exhaustive.

                                       26
<PAGE>


                                   APPENDIX A

               FAIRNESS OPINION OF MCCONNELL, BUDD & DOWNES, INC.

                 [LETTERHEAD OF McCONNELL, BUDD & DOWNES, INC.]


                                                         March 31, 2000

The Board of Directors
NBT Bancorp Inc.
52 South Broad Street
Norwich, New York 13815

The Board of Directors:

     You have requested our opinion as to the fairness,  from a financial  point
of view, to the  stockholders of' NBT Bancorp Inc. ("NBT") of the Exchange Ratio
governing the exchange of shares of the common stock of Pioneer American Holding
Company Corp. (Pioneer American) for shares of common stock of NBT in connection
with  the  proposed  acquisition  of  Pioneer  American  by NBT  pursuant  to an
Agreement and Plan of Merger (the "Merger  Agreement') dated December 7, 1999 by
and between Pioneer American and NBT. Pursuant to the Merger Agreement,  Pioneer
American will merge with and into NBT, with NBT being the surviving corporation.

     As  is  more  specifically  set  forth  in  the  Merger   Agreement,   upon
consummation of the merger,  each  outstanding  share of Pioneer American common
stock, except for shares held by NBT and its subsidiaries or by Pioneer American
and its  subsidiaries  (in both  cases,  other than  shares  held in a fiduciary
capacity or as a result of debts previously contracted),  will be exchanged into
1.805 shares of NBT Common Stock.  The Merger  Agreement may be terminated under
certain  conditions  prior to the  effective  time of the merger by the Board of
Directors of either party based on defined criteria.

     McConnell, Budd & Downes, Inc., as part of its investment banking business,
is  regularly  engaged in the  valuation of bank  holding  companies  and banks,
thrift  holding  companies and thrifts and their  securities in connection  with
mergers  and  acquisitions,   negotiated   underwritings,   private  placements,
competitive bidding processes,  market making as a NASD market maker,  secondary
distributions  of listed  securities and  valuations  for corporate,  estate and
other purposes.  Our experience and familiarity  with NBT includes having worked
as a financial  advisor to NBT since October 20, 1994 on a contractual basis and
specifically  includes our participation in the process and negotiations leading
up to the proposed  merger with Pioneer  American.  In the course of our role as
financial  advisor to NBT in connection  with the merger,  we have received fees
for our services and will receive  additional  fees contingent on the occurrence
of certain defined events.  While the payment of all or a significant portion of
fees  related  to  financial  advisory  services  provided  in  connection  with
arm's-length   mergers  and  other  business   combination   transactions   upon
consummation of such transactions,  as is the case with this transaction,  might
be viewed  as  giving  such  financial  advisors  a  financial  interest  in the
successful completion of such transactions,  such compensation  arrangements are
standard  and  customary  for   transactions  of  the  size  and  type  of  this
transaction.

     In arriving at our opinion, we have reviewed the Merger Agreement.  We have
also reviewed publicly available business, financial and shareholder information
relating to NBT and its subsidiaries and certain  publicly  available  financial
and shareholder information relating to Pioneer American.

     In connection with the foregoing,  we have (i) reviewed Pioneer  American's
Annual  Reports  to  Stockholders,  Annual  Reports  on Form  10-K  and  related
financial  information  for the four calendar  years ended December 31, 1998 and
Pioneer American's Quarterly Report on Form 10-Q and related unaudited financial
information for 1999; (ii) reviewed NBT's Annual Reports to Stockholders, Annual
Reports on Form 10-K and related  financial  information  for the four  calendar
years  ended  December  31,  1998 and  NBT's  Quarterly  Report on Form 10-Q and
related  unaudited  financial  information  for  1999;  (iii)  reviewed  certain
internal financial information

                                       27
<PAGE>


and financial forecasts,  relating to the business, earnings, cash flows, assets
and prospects of the respective companies furnished to McConnell, Budd & Downes,
Inc. by Pioneer  American  and NBT,  respectively;  (iv) held  discussions  with
members  of the  senior  management  and  board of NBT  concerning  the past and
current  results of  operations  of NBT,  its current  financial  condition  and
management's opinion of its future prospects;  (v) held discussions with members
of senior management of Pioneer American concerning the past and current results
of  operations  of  Pioneer  American,   its  current  financial  condition  and
management's  opinion of its future  prospects;  (vi)  reviewed  the  historical
record of reported prices, trading volume and dividend payments for both NBT and
Pioneer American common stock;  (vii) considered the current state of and future
prospects  for the  economy  of New  York  and  Pennsylvania  generally  and the
relevant  market  areas  for NBT and  Pioneer  American  in  particular;  (viii)
reviewed  specific merger analysis models employed by McConnell,  Budd & Downes,
Inc. to evaluate potential business combinations of financial institutions; (ix)
reviewed the reported  financial terms of selected recent business  combinations
in the banking  industry;  and (x) performed  such other studies and analyses as
McConnell,  Budd & Downes, Inc.  considered  appropriate under the circumstances
associated with this particular transaction.

     In the course of our review and analysis we considered, among other things,
such topics as the historical and projected  future  contributions  of recurring
earnings by the parties,  the anticipated  future earnings per share results for
the parties on both a combined and stand-alone  basis,  the potential to realize
significant  recurring  operating  expense  reductions and the impact thereof on
projected  future earnings per share,  the relative  capitalization  and capital
adequacy of each of the parties, the availability of non-interest income to each
of the parties,  the relative asset quality and apparent adequacy of the reserve
for loan losses for each of the parties.  We also  considered the composition of
deposits and the  composition of the loan portfolio of each of Pioneer  American
and NBT. In addition,  we  considered  the  historical  trading  range,  trading
pattern  and  relative  market  liquidity  of the  common  shares of each of the
parties.  In the  conduct of our review and  analysis  we have  relied  upon and
assumed, without independent verification,  the accuracy and completeness of the
financial  information  provided  to us by  Pioneer  American  and  NBT  and  or
otherwise publicly  obtainable.  In reaching our opinion we have not assumed any
responsibility  for the  independent  verification  of such  information  or any
independent  valuation or appraisal of any of the assets or the  liabilities  of
either Pioneer American or NBT, nor have we obtained from any other source,  any
current  appraisals of the assets or liabilities  of either Pioneer  American or
NBT. We have also relied on the management of Pioneer American and NBT as to the
reasonableness  of  various  financial  and  operating   forecasts  and  of  the
assumptions  on which they are based,  which were  provided to us for use in our
analyses.

     In the course of rendering  this opinion,  which is being rendered prior to
the  receipt  of  certain  required   regulatory   approvals   necessary  before
consummation of the merger,  we assume that no conditions will be imposed by any
regulatory agency in connection with its approval of the merger that will have a
material adverse effect on the results of operations, the financial condition or
the prospects of NBT following consummation of the merger.

     Based upon and subject to the foregoing,  it is our opinion, that as of the
date of this letter,  the exchange ratio is fair to the stockholders of NBT from
a financial point of view.

                                            Very truly yours,


                                           /s/ McConnell, Budd & Downes, Inc.

                                       28
<PAGE>


                                   APPENDIX B

             FAIRNESS OPINION OF DANIELSON ASSOCIATES INC.


                      [LETTERHEAD OF DANIELSON ASSOCIATES]


                                                               April 20, 2000


Board of Directors
Pioneer American Holding Company Corporation
41 North Main Street
Carbondale, Pennsylvania  18407

Dear Members of the Board:

     Set forth  herein is the  updated  opinion  of  Danielson  Associates  Inc.
("Danielson  Associates")  as to the "fairness" of the offer by NBT Bancorp Inc.
("NBT")  of  Norwich,  New York to acquire  all of the  common  stock of Pioneer
American Holding Company  Corporation  ("Pioneer") of Carbondale,  Pennsylvania.
The  "fair"  sale  value is  defined  as the price at which all of the shares of
Pioneer's common stock would change hands between a willing seller and a willing
buyer, each having reasonable  knowledge of the relevant facts. In opining as to
the  "fairness"  of the offer,  it also had to be  determined  if the NBT common
stock that is to be exchanged for Pioneer stock is "fairly" valued.

     In  preparing  the  original   opinion,   Pioneer  and  NBT's  markets  and
performance  were analyzed and their business and prospects  were  reviewed.  We
also conducted such other financial  analyses as we deemed  appropriate  such as
comparable company analyses, comparable transactions and pro forma dilution. Any
unique characteristics also were considered.

     On April 20,  2000,  NBT  announced  that it had  agreed to merge  with BSB
Bancorp,  Inc. ("BSB") of Binghampton,  New York. The agreement calls for, among
other things, that the "principal" office of the combined  organization to be in
Binghampton,  a new name for the surviving  corporation and a board of directors
with similar  representation  from NBT and BSB. We have  included an analysis of
BSB and the  specifics of the merger  agreement  in our revised  opinion as this
merger agreement represents a material change.

     We also conducted a limited review of the due diligence  analysis completed
by NBT on BSB. This included interviews of key NBT officers who were involved in
the due diligence, lending officers and senior management at BSB and consultants
hired by NBT. We also  reviewed the written  materials  gathered and produced by
NBT's due diligence team.

     This opinion is based partly on data  supplied to Danielson  Associates  by
Pioneer  and NBT,  but it relied  on some  public  information  all of which was
believed  to be  reliable,  but neither the  completeness  nor  accuracy of such
information could be guaranteed.  In particular,  the opinion has assumed, based
on NBT's  management's  representation,  that  there were no  significant  asset
quality  problems at NBT beyond what was stated in recent  reports to regulatory
agencies and in the monthly report to the  directors;  and that the additions to
reserves  being made at BSB were  sufficient  to cover any likely asset  quality
deterioration that might be forthcoming as a result of merging BSB into NBT.

     In determining the "fair" sale value of Pioneer,  the primary  emphasis was
on prices paid relative to earnings for  Pennsylvania  and Northeast  banks that
had similar financial, structural and market characteristics.  These prices were
then related to assets and equity capital, also referred to as "book."

                                       29
<PAGE>


     The "fair"  market value of NBT's common stock to be exchanged  for Pioneer
stock was determined by a comparison with other similar bank holding  companies.
This  comparison  showed  NBT stock to be valued  below  that of the  comparable
banks.

     In the original  opinion,  based on Pioneer's  recent  performance  and its
future   potential,   comparisons   with   similar   transactions   and   unique
characteristics,  it was  determined  that its "fair" sale value was between $80
and $89  million,  or $27.67 to $30.76 per  share.  Thus,  NBT's  offer of $87.5
million,  or $29.22 per share, was a "fair" offer from a financial point of view
for Pioneer and its shareholders.

     There has been no subsequent,  significant change in NBT's performance, but
its stock price has declined by about 28%, which generally  reflects the decline
in bank stock  prices  during this period.  Thus,  if the "fair" value range and
change in the offer value are adjusted to reflect market  conditions as of April
20,  2000,  the value of NBT's offer is still  "fair" from a financial  point of
view to Pioneer American and its shareholders.

                                     Respectfully submitted,



                                     /s/ Arnold G. Danielson
                                     Chairman
                                     Danielson Associates Inc.

AGD:msf
                                     Enclosure

                                       30
<PAGE>


                 PART II: INFORMATION NOT REQUIRED IN PROSPECTUS


ITEM 21. EXHIBITS AND FINANCIAL STATEMENTS.

(a)The following  exhibits are filed as part of this  Registration  Statement or
incorporated herein by reference:

<TABLE>
<CAPTION>
Exhibit No.           Description
- -----------           -----------
<S>                  <C>
23.1                  Consent of KPMG LLP, independent auditors for NBT Bancorp Inc.*

23.2                  Consent of KPMG LLP, independent auditors for Pioneer American Holding Company Corp.*

23.3                  Consent of PricewaterhouseCoopers LLP, independent accountants for BSB Bancorp, Inc.*

23.4                  Consent of Danielson Associates Inc. *

23.5                  Consent of McConnell, Budd & Downes, Inc. *

99.1                  Opinion of McConnell, Budd & Downes, Inc. as to the fairness of the transaction to NBT (attached as Appendix A
                      to the Supplement included in this Registration Statement).

99.2                  Opinion of Danielson Associates Inc. as to the fairness of the transaction to stockholders of Pioneer American
                      (attached as Appendix B to the Supplement included in this Registration Statement).
</TABLE>

- ---------------
*  Filed herewith.

     (b)  No financial  statement  schedules  are required to be filed  herewith
          pursuant to Item 21(b) of this Form.

     (c)  The fairness opinion of McConnell,  Budd & Downes, Inc. is attached as
          Appendix A to the Supplement included in this Registration  Statement.
          The  fairness  opinion of  Danielson  Associates  Inc.  is attached as
          Appendix B to the Supplement included in this Registration Statement.

ITEM 22. UNDERTAKINGS.

     The undersigned registrant hereby undertakes as follows:

     (1) that,  for purposes of determining  any liability  under the Securities
Act of 1933, each filing of the  registrant's  annual report pursuant to Section
13(a)  or  Section  15(d)  of the  Securities  Exchange  Act  of  1934  that  is
incorporated by reference in the registration  statement shall be deemed to be a
new registration  statement relating to the securities offered therein,  and the
offering of such  securities at that time shall be deemed to be the initial bona
fide offering thereof.

     (2) to deliver or cause to be delivered with the prospectus, to each person
to whom the  prospectus  is sent or given,  the latest annual report to security
holders  that is  incorporated  by  reference in the  prospectus  and  furnished
pursuant to and meeting the  requirements  of Rule 14a-3 or Rule 14c-3 under the
Securities  Exchange  Act of 1934;  and,  where  interim  financial  information
required to be presented by Article 3 of Regulation  S-X is not set forth in the
prospectus,  to  deliver,  or cause to be  delivered  to each person to whom the
prospectus is sent or given,  the latest  quarterly  report that is specifically
incorporated  by reference in the  prospectus to provide such interim  financial
information.

     (3) that  prior  to any  public  reoffering  of the  securities  registered
hereunder  through the use of a prospectus which is a part of this  registration
statement,  by any person or party who is deemed to be an underwriter within the

<PAGE>


meaning of Rule 145(c), such reoffering  prospectus will contain the information
called for by the  applicable  registration  form with respect to reofferings by
persons who may be deemed  underwriters,  in addition to the information  called
for by the other items of the applicable form.

     (4) that every  prospectus  (i) that is filed  pursuant  to  paragraph  (3)
immediately preceding, or (ii) that purports to meet the requirements of Section
10(a)(3) of the  Securities  Act of 1933, as amended,  and is used in connection
with an offering of  securities  subject to Rule 415, will be filed as a part of
an  amendment  to the  registration  statement  and will not be used  until such
amendment is  effective,  and that,  for purposes of  determining  any liability
under the Securities Act of 1933,  each such  post-effective  amendment shall be
deemed to be a new  registration  statement  relating to the securities  offered
therein,  and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

     (5) that  insofar as  indemnification  for  liabilities  arising  under the
Securities Act of 1933 may be permitted to directors,  officers and  controlling
persons of the  registrant  pursuant to the provisions  described  under Item 20
above, or otherwise,  the registrant has been advised that in the opinion of the
Securities and Exchange Commission such indemnification is against public policy
as expressed in the Act and is,  therefore,  unenforceable.  In the event that a
claim for  indemnification  against such liabilities  (other than the payment by
the  registrant  of  expenses  incurred  or  paid  by  a  director,  officer  or
controlling  person of the registrant in the  successful  defense of any action,
suit or proceeding) is asserted by such director,  officer or controlling person
in connection with the securities being registered,  the registrant will, unless
in the  opinion  of its  counsel  the matter  has been  settled  by  controlling
precedent,  submit to a court of appropriate  jurisdiction  the question whether
such  indemnification by it is against public policy as expressed in the Act and
will be governed by the final adjudication of such issue.

     (6) to  respond  to  requests  for  information  that  is  incorporated  by
reference into the Joint Proxy Statement/Prospectus  pursuant to Items 4, 10(b),
11 or 13 of Form S-4, within one business day of receipt of such request, and to
send the  incorporated  documents  by first class mail or other  equally  prompt
means. This includes information  contained in documents filed subsequent to the
Effective Date of the registration  statement  through the date of responding to
the request.

     (7) to  supply  by  means of a  post-effective  amendment  all  information
concerning a transaction,  and the company being acquired involved therein, that
was not the subject of and included in the registration statement when it became
effective.

     (8) to file,  during any period in which  offers or sales are being made, a
post-effective amendment to this registration statement:

          (i) to include  any  prospectus  required  by Section  10(a)(3) of the
     Securities Act of 1933;

          (ii) to reflect in the  prospectus  any facts or events  arising after
     the  effective  date of the  registration  statement  (or the  most  recent
     post-effective amendment thereof) which,  individually or in the aggregate,
     represent  a  fundamental  change  in  the  information  set  forth  in the
     registration statement.

          (iii) to include any material  information with respect to the plan of
     distribution not previously disclosed in the registration  statement or any
     material change to such information in the registration statement.

     (9) to remove from registration by means of a post-effective  amendment any
of the securities being registered which remain unsold at the termination of the
offering.


<PAGE>
                                   SIGNATURES

     Pursuant to the  requirements of the Securities Act of 1933, the registrant
has duly caused this  registration  statement  to be signed on its behalf by the
undersigned,  thereunto duly authorized, in Norwich, New York on this 9th day of
May, 2000.

                                          NBT Bancorp Inc.

                                          /s/ Michael J. Chewens
                                          ----------------------
                                          By: Michael J. Chewens
                                          Executive Vice President, Chief
                                          Financial Officer and Treasurer

     Pursuant  to  the   requirements  of  the  Securities  Act  of  1933,  this
registration  statement  has  been  signed  by  the  following  persons  in  the
capacities and on the dates indicated.

<TABLE>
<CAPTION>
SIGNATURE                           CAPACITY                                  DATE
- ---------                           --------                                  ----
<S>                                <C>                                       <C>
/s/ Daryl R. Forsythe*              President, Chief Executive Officer           May 9, 2000
- ---------------------               and Director (Principal Executive
Daryl R. Forsythe                   Officer)


/s/ Michael J. Chewens              Executive Vice President,                    May 9, 2000
- ----------------------              Chief Financial Officer, and Treasurer
Michael J. Chewens                  of NBT and NBT Bank (Principal
                                    Financial and Accounting Officer)

/s/ Everett A. Gilmour*             Chairman of the Board of Directors           May 9, 2000
- ----------------------
Everett A. Gilmour

/s/ J. Peter Chaplin*               Director                                     May 9, 2000
- --------------------
J. Peter Chaplin

/s/ Peter B. Gregory*               Director                                     May 9, 2000
- --------------------
Peter B. Gregory

                                    Director                                          , 2000
- ----------------------
William C. Gumble

                                    Director                                          , 2000
- ----------------------
Bruce D. Howe

                                    Director                                          , 2000
- --------------------------
Andrew S. Kowalczyk, Jr.

/s/ Dan B. Marshman*                Director                                     May 9, 2000
- -------------------
Dan B. Marshman

                                    Director                                          , 2000
- --------------------------
John G. Martines

/s/ John C. Mitchell*               Director                                     May 9, 2000
- --------------------
John C. Mitchell

                                    Director                                          , 2000
- -------------------------
William L. Owens

/s/ Paul O. Stillman*               Director                                     May 9, 2000
- --------------------
Paul O. Stillman

</TABLE>

* By: /s/ Michael J. Chewens
      ------------------------------
      Michael J. Chewens, Attorney-in-Fact
      Pursuant to Power of Attorney


<PAGE>



                                  EXHIBIT INDEX

<TABLE>
<CAPTION>
Exhibit No.           Description
- -----------           -----------
<S>                  <C>

23.1                  Consent of KPMG LLP, independent auditors for NBT Bancorp Inc.*

23.2                  Consent of  KPMG LLP, independent auditors for Pioneer American Holding Company Corp.*

23.3                  Consent of  PricewaterhouseCoopers LLP, independent accountants for BSB Bancorp, Inc.*

23.4                  Consent of Danielson Associates Inc. *

23.5                  Consent of McConnell, Budd & Downes, Inc. *

99.1                  Opinion of McConnell, Budd & Downes, Inc. as to the fairness of the transaction to NBT (attached as Appendix A
                      to the Supplement included in this Registration Statement).

99.2                  Opinion of Danielson Associates Inc. as to the fairness of the transaction to stockholders of Pioneer American
                      (attached as Appendix B to the Supplement included in this Registration Statement).
</TABLE>

- ---------------------
*  Filed herewith.



                                NBT BANCORP INC.

               Proxy Solicited on Behalf of the Board of Directors

     The undersigned  hereby appoints James I. Dunne and Adelbert L. Button, and
either of them,  with full  power of  substitution,  proxies  to  represent  the
undersigned at the adjourned  Annual Meeting of Stockholders of NBT Bancorp Inc.
("NBT")  to  be  reconvened  at  the  Holiday  Inn  Arena,  2-8  Hawley  Street,
Binghamton,  New  York on June  20,  2000 at 2:00  p.m.  local  time,  or at any
adjournment or postponement  thereof (the  "Meeting"),  with all power which the
undersigned would possess if personally present, and to vote all shares of NBT's
common stock which the  undersigned may be entitled to vote at said Meeting upon
the following proposals described in the accompanying supplement,  in accordance
with the following instructions and, at their discretion, upon any other matters
that may properly come before the Meeting.  THIS PROXY, WHEN PROPERLY  EXECUTED,
WILL BE VOTED AS DIRECTED BY THE UNDERSIGNED. IF NO DIRECTION IS INDICATED, THIS
PROXY  WILL BE VOTED FOR THE  ISSUANCE  OF NBT  COMMON  STOCK IN THE  MERGER AND
RATIFICATION OF THE MERGER AGREEMENT.

1.   To  approve  the  issuance  by NBT  of  its  common  stock  to  the  former
     stockholders  of Pioneer  American  Holding Company Corp. in the merger and
     ratify the Agreement and Plan of Merger,  dated as of December 7, 1999, and
     amended as of March 7,  2000,  by and  between  NBT and  Pioneer  American,
     which,  if  completed,  would result in (a) the merger of Pioneer  American
     with a subsidiary  of NBT, (b) the  subsequent  merger of Pioneer  American
     into NBT,  and (c) the  issuance  of 1.805  shares of NBT  common  stock in
     exchange for each share of Pioneer  American  common stock,  and all of the
     matters contemplated by the merger agreement.

    [_] FOR           [_] AGAINST           [_] ABSTAIN

2.   The  proxies are  authorized  to vote in their  discretion  upon such other
     business that may properly come before the Meeting.

X  Please mark your votes as in this example.

 (Continued and to be signed on reverse side)   SEE REVERSE SIDE

(Continued from other side)

     [_] Check here for address change and note change below

     [_] Check here if you plan to attend the Meeting

New

address:

  Date:                                     Signature(s)
         ------------------------




                    Please sign here  exactly as name(s)  appear(s) on the left.
                    When signing as attorney, executor, administrator,  trustee,
                    guardian,  or in any  other  fiduciary  capacity,  give full
                    title.  If more than one person acts as trustee,  all should
                    sign. All joint owners must sign.

                     PIONEER AMERICAN HOLDING COMPANY CORP.

<PAGE>

                 Proxy Solicited on Behalf of Board of Directors

     The undersigned hereby appoints Daniel Corazzi,  John Kuna and Basil Telep,
or any one or more of them, with full power of  substitution,  proxies,  to vote
all  of  the  stock  of  Pioneer  American  Holding  Company  Corp.,  which  the
undersigned is entitled to vote at the adjourned Special Meeting of Stockholders
of Pioneer American to be reconvened at Heart Lake Lodge,  1299 Heart Lake Road,
Jermyn,  Pennsylvania  on June 20,  2000 at  10:00  a.m.  local  time and at any
adjournment or postponement thereof. THIS PROXY, WHEN PROPERLY EXECUTED, WILL BE
VOTED, AS DIRECTED BY THE UNDERSIGNED. IF NO DIRECTION IS MADE, IT WILL BE VOTED
FOR THE FOLLOWING PROPOSAL.

1.   To approve the Agreement and Plan of Merger,  dated as of December 7, 1999,
     and amended as of March 7, 2000,  by and between  Pioneer  American and NBT
     Bancorp Inc. ("NBT"),  which would result in the merger of Pioneer American
     into NBT and the  issuance of 1.805  shares of NBT common stock in exchange
     for each share of Pioneer  American  common  stock,  and all of the matters
     contemplated by the merger agreement.

    [_] FOR                       [_] AGAINST                     [_] ABSTAIN

2.   The  proxies are  authorized  to vote in their  discretion  upon such other
     business  that may  properly  come  before the Pioneer  American  adjourned
     special meeting.

X  Please mark your votes as in this example.

 (Continued and to be signed on reverse side)   SEE REVERSE SIDE

(Continued from other side)



  Date:                                  Signature(s)
         --------------------------
                                              --------------------------

                                              --------------------------

                                              --------------------------

                    Please sign here  exactly as name(s)  appear(s) on the left.
                    When signing as attorney, executor, administrator,  trustee,
                    guardian,  or in any  other  fiduciary  capacity,  give full
                    title.  If more than one person acts as trustee,  all should
                    sign. All joint owners must sign.




                                  EXHIBIT 23.1

                         CONSENT OF INDEPENDENT AUDITORS

The Board of Directors
NBT Bancorp Inc.:

     We consent to incorporation by reference in Post-Effective  Amendment No. 1
to the  registration  statement on Form S-4 of NBT Bancorp  Inc.  related to the
registration  of shares for the merger  between  NBT  Bancorp  Inc.  and Pioneer
American  Holding Company Corp.,  filed by NBT Bancorp Inc. under the Securities
Act of 1933 of our audit  report  dated  January 21,  2000,  with respect to the
consolidated  balance  sheets of NBT Bancorp Inc. and  subsidiary as of December
31,  1999  and  1998,  and  the  related  consolidated   statements  of  income,
stockholders'  equity, cash flows and comprehensive income for each of the years
in the  three-year  period ended  December 31, 1999 which report  appears in the
December 31, 1999 annual report on Form 10-K of NBT Bancorp  Inc.,  incorporated
by  reference  herein,  and to the  reference  to our  firm  under  the  heading
"Experts"  in  the  Supplemental  Joint  Proxy   Statement/Prospectus   and  the
registration statement referred to above.

     We consent to incorporation by reference in Post-Effective  Amendment No. 1
to the  registration  statement on Form S-4 of NBT Bancorp  Inc.  related to the
registration  of shares for the merger  between  NBT  Bancorp  Inc.  and Pioneer
American  Holding Company Corp.,  filed by NBT Bancorp Inc. under the Securities
Act of 1933 of our audit  report  dated  March 10,  2000,  with  respect  to the
supplemental consolidated balance sheets of NBT Bancorp Inc. and subsidiaries as
of  December  31,  1999 and  1998,  and the  related  supplemental  consolidated
statements of income,  stockholders' equity, cash flows and comprehensive income
for each of the years in the  three-year  period  ended  December 31, 1999 which
report appears in the Current Report on Form 8-K dated March 31, 2000,  filed by
NBT Bancorp Inc., incorporated by reference herein.

/s/ KPMG LLP
KPMG LLP

Syracuse, New York
                                                    May 10, 2000






                                  EXHIBIT 23.2

                         CONSENT OF INDEPENDENT AUDITORS

The Board of Directors
Pioneer American Holding Company Corp.

       We consent to incorporation by reference in Post-Effective  Amendment No.
1 to the  registration  statement  on Form S-4 of NBT Bancorp  Inc. of our audit
report dated January 21, 2000,  relating to the  consolidated  balance sheets of
Pioneer  American  Holding  Company Corp. and subsidiary as of December 31, 1999
and 1998,  and the related  consolidated  statements of  operations,  changes in
stockholders'  equity,  and cash  flows for each of the years in the  three-year
period ended December 31, 1999 which report has been  incorporated  by reference
in the December 31, 1999 annual report on Form 10-K of Pioneer  American Holding
Company Corp.,  incorporated  by reference  herein,  and to the reference to our
firm under the heading "Experts" in the Supplement.

/s/ KPMG LLP
- ------------
KPMG LLP
Philadelphia, Pennsylvania
May 5, 2000






                                  EXHIBIT 23.3

                       CONSENT OF INDEPENDENT ACCOUNTANTS

     We hereby consent to the incorporation by reference in this  Post-Effective
Amendment No. 1 to the registration statement on Form S-4 of NBT Bancorp Inc. of
our report dated January 21, 2000,  relating to the financial  statements of BSB
Bancorp,  Inc., which appears in the 1999 Annual Report to Shareholders which is
incorporated  by reference in its Annual  Report on Form 10-K for the year ended
December 31, 1999.  We also  consent to the  references  to us under the heading
"Experts" in such Post-Effective Amendment No. 1.

/s/ PricewaterhouseCoopers LLP
PricewaterhouseCoopers LLP
Syracuse, New York
May 9, 2000







                                  EXHIBIT 23.4

                          CONSENT OF FINANCIAL ADVISOR

                      CONSENT OF DANIELSON ASSOCIATES INC.

     We  hereby  consent  to  the  use of  our  firm's  name  in  the  Form  S-4
Registration  Statement  of NBT Bancorp  Inc.  relating to the  registration  of
shares of NBT Bancorp  Inc.  common  stock to be issued in  connection  with the
proposed  acquisition of Pioneer  American Holding Company Corp. We also consent
to the  inclusion  of our  opinion  letter as an  Appendix  to the  Joint  Proxy
Statement/Prospectus  included as part of the Form S-4  Registration  Statement,
and  to  the   references   to  our   opinion   included   in  the  Joint  Proxy
Statement/Prospectus.

                                    DANIELSON ASSOCIATES INC.



                                    By:     /s/ Arnold G. Danielson
                                            Arnold G. Danielson
                                            Chairman

May 9, 2000







                                  EXHIBIT 23.5

                          CONSENT OF FINANCIAL ADVISOR

     We hereby  consent to the  inclusion  of the Opinion of  McConnell,  Budd &
Downes,  Inc. in the  Post-Effective  Amendment No. 1 to Form S-4 of NBT Bancorp
Inc.  ("NBT")  and Joint Proxy  Statement  to be filed with the  Securities  and
Exchange  Commission in connection  with the proposed  Consolidation  of NBT and
Pioneer  American  Holding  Company  Corp.  and to the  references  to the  work
completed  by our firm as  financial  advisor to NBT,  therein.  In giving  such
consent,  we do not thereby  admit that we come  within the  category of persons
whose consent is required  under Section 7 of the  Securities Act of 1933 or the
rules and regulations of the Securities and Exchange Commission thereunder,  nor
do we  thereby  admit  that we are  experts  with  respect  to any  part of such
Registration  Statement  within the meaning of the term  "expert" as used in the
Securities  Act of  1933,  as  amended,  or the  rules  and  regulations  of the
Securities and Exchange Commission thereunder.

/s/ McConnell, Budd & Downes, Inc.
May 8, 2000





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