SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                   ---------

                                    FORM 8-K

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


Date of Report (Date of earliest event reported)       December 7, 1999
                                                 -------------------------------


                                NBT Bancorp Inc.
--------------------------------------------------------------------------------
                  (Exact Name of Registrant as Specified in Charter)


         Delaware                      0-14703                  16-1268674
--------------------------------------------------------------------------------
   (State or Other Jurisdiction      (Commission              (IRS Employer
         of Incorporation)           File Number)         Identification Number)


   52 South Broad Street, Norwich, New York                         13815
--------------------------------------------------------------------------------
(Address of Principal Executive Office)                           (Zip Code)


Registrant's telephone number, including area code        607/337-2265
                                                    ----------------------------


                                      N/A
--------------------------------------------------------------------------------
          (Former Name or Former Address, if Changed Since Last Report)


<PAGE>

Item 5. Other Events.

         On December 7, 1999, NBT Bancorp Inc., a Delaware  corporation ("NBT"),
and Pioneer American Holding Company Corp., a Pennsylvania corporation ("Pioneer
American"),  announced  that  they had  entered  into an  Agreement  and Plan of
Merger, dated as of December 7, 1999 (the "Merger Agreement").

         Pursuant to the Merger Agreement,  Pioneer American will merge with and
into NBT, with NBT being the surviving corporation (the "Merger").  Shareholders
of Pioneer  American  will  receive a fixed ratio of 1.805  shares of NBT common
stock for each share exchanged.  Based on the December 7, 1999, closing price of
NBT common stock on the Nasdaq National Market, NBT will issue approximately 5.2
million shares and share equivalents in exchange for all of the Pioneer American
common stock and share  equivalents  outstanding.  Pioneer American has provided
NBT an option to acquire up to 569,997 shares of Pioneer American's common stock
(equivalent to 19.9% of Pioneer  American's common stock currently  outstanding)
exercisable in the event of certain  circumstances  involving  transactions with
third parties,  acts of third parties, or break-up of the Merger Agreement.  The
Merger is subject to the approval of each company's  shareholders and of banking
regulators. The Merger is expected to close in the second quarter of 2000 and is
intended  to be  accounted  for as a  pooling-of-interests  and to  qualify as a
tax-free  exchange for Lake Ariel  shareholders.  The  transaction  is valued at
$84.48 million or $29.33 per share for the  outstanding  common stock of Pioneer
American.

Item 7.  Financial Statements, Pro Forma Financial Information and Exhibits.

                  (a) Not Applicable.

                  (b) Not Applicable.

                  (c) Exhibits.


         The  following   exhibits  are  filed  with  this  Current   Report  or
incorporated by reference into this Current Report on Form 8-K:


Exhibit
Number            Description
-------           -----------

2.1               Agreement and Plan of Merger, dated as of December 7, 1999, by
                  and among NBT  Bancorp  Inc.,  Levon  Acquisition  Company and
                  Pioneer American Holding Company Corp. *

<PAGE>

2.2               The  Directors'  Agreement,  dated as of December 7, 1999,  is
                  part of the  Agreement  and Plan of Merger,  which is filed as
                  Exhibit 2.1 above.

2.3               Stock Option Agreement, dated December 7, 1999, by and between
                  Pioneer  American  Holding  Company  Corp. as "Issuer" and NBT
                  Bancorp Inc. as "Grantee." *

2.4               Form of Employment Agreement with John W. Reuther. *

2.5               Form of Change-in-Control Agreement. *

2.6               Shareholders Voting Agreement. *

99.1              Press release, dated December 8, 1999.

*    Incorporated  by  reference  to the  corresponding  exhibit  number  in the
Registrant's  Schedule 13D filed by the  Registrant on December 16, 1999    with
respect to Pioneer American Holding Company Corp., File No. 0-14506.


                                    SIGNATURE

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

                                             NBT BANCORP INC.


                                             By:  /s/ Daryl R. Forsythe
                                                  ------------------------------
                                                  Name: Daryl R. Forsythe
                                                  Title: President and Chief
                                                         Executive Officer

Date:  December 16, 1999.


<PAGE>


                                  EXHIBIT INDEX

99.1              Press release, dated December 8, 1999.
[{"type": "8-K", "sequence": "1", "description": "FORM 8-K", "secsgml_size_bytes": 5600}]
{"company-data": {"conformed-name": "NBT BANCORP INC", "cik": "0000790359", "assigned-sic": "6021", "irs-number": "161268674", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "000-14703", "film-number": "99775863"}, "business-address": {"street1": "52 S BROAD ST", "city": "NORWICH", "state": "NY", "zip": "13815", "phone": "6073376000"}, "mail-address": {"street1": "52 S. BROAD STREET", "city": "NORWICH", "state": "NY", "zip": "13815"}}
SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                   ---------

                                    FORM 8-K

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

Date of Report (Date of earliest event reported)       December 7, 1999
                                                 -------------------------------

                                NBT Bancorp Inc.
--------------------------------------------------------------------------------
                  (Exact Name of Registrant as Specified in Charter)

         Delaware                      0-14703                  16-1268674
--------------------------------------------------------------------------------
   (State or Other Jurisdiction      (Commission              (IRS Employer
         of Incorporation)           File Number)         Identification Number)

   52 South Broad Street, Norwich, New York                         13815
--------------------------------------------------------------------------------
(Address of Principal Executive Office)                           (Zip Code)

Registrant's telephone number, including area code        607/337-2265
                                                    ----------------------------

                                      N/A
--------------------------------------------------------------------------------
          (Former Name or Former Address, if Changed Since Last Report)
Item 5. Other Events.

         On December 7, 1999, NBT Bancorp Inc., a Delaware  corporation ("NBT"),
and Pioneer American Holding Company Corp., a Pennsylvania corporation ("Pioneer
American"),  announced  that  they had  entered  into an  Agreement  and Plan of
Merger, dated as of December 7, 1999 (the "Merger Agreement").

         Pursuant to the Merger Agreement,  Pioneer American will merge with and
into NBT, with NBT being the surviving corporation (the "Merger").  Shareholders
of Pioneer  American  will  receive a fixed ratio of 1.805  shares of NBT common
stock for each share exchanged.  Based on the December 7, 1999, closing price of
NBT common stock on the Nasdaq National Market, NBT will issue approximately 5.2
million shares and share equivalents in exchange for all of the Pioneer American
common stock and share  equivalents  outstanding.  Pioneer American has provided
NBT an option to acquire up to 569,997 shares of Pioneer American's common stock
(equivalent to 19.9% of Pioneer  American's common stock currently  outstanding)
exercisable in the event of certain  circumstances  involving  transactions with
third parties,  acts of third parties, or break-up of the Merger Agreement.  The
Merger is subject to the approval of each company's  shareholders and of banking
regulators. The Merger is expected to close in the second quarter of 2000 and is
intended  to be  accounted  for as a  pooling-of-interests  and to  qualify as a
tax-free  exchange for Lake Ariel  shareholders.  The  transaction  is valued at
$84.48 million or $29.33 per share for the  outstanding  common stock of Pioneer
American.

Item 7.  Financial Statements, Pro Forma Financial Information and Exhibits.

                  (a) Not Applicable.

                  (b) Not Applicable.

                  (c) Exhibits.

         The  following   exhibits  are  filed  with  this  Current   Report  or
incorporated by reference into this Current Report on Form 8-K:

Exhibit
Number            Description
-------           -----------

2.1               Agreement and Plan of Merger, dated as of December 7, 1999, by
                  and among NBT  Bancorp  Inc.,  Levon  Acquisition  Company and
                  Pioneer American Holding Company Corp. *
2.2               The  Directors'  Agreement,  dated as of December 7, 1999,  is
                  part of the  Agreement  and Plan of Merger,  which is filed as
                  Exhibit 2.1 above.

2.3               Stock Option Agreement, dated December 7, 1999, by and between
                  Pioneer  American  Holding  Company  Corp. as "Issuer" and NBT
                  Bancorp Inc. as "Grantee." *

2.4               Form of Employment Agreement with John W. Reuther. *

2.5               Form of Change-in-Control Agreement. *

2.6               Shareholders Voting Agreement. *

99.1              Press release, dated December 8, 1999.

*    Incorporated  by  reference  to the  corresponding  exhibit  number  in the
Registrant's  Schedule 13D filed by the  Registrant on December 16, 1999    with
respect to Pioneer American Holding Company Corp., File No. 0-14506.

                                    SIGNATURE

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

                                             NBT BANCORP INC.

                                             By:  /s/ Daryl R. Forsythe
                                                  ------------------------------
                                                  Name: Daryl R. Forsythe
                                                  Title: President and Chief
                                                         Executive Officer

Date:  December 16, 1999.
EXHIBIT INDEX

99.1              Press release, dated December 8, 1999.