NEWS RELEASE

Date:           July 15, 2005     12:00 p.m. E.S.T.
Contact:        James L. Saner, Sr., President and CEO
                MainSource Financial Group, Inc.  812-663-0157

                                               [MainSource Financial Group logo]

                      MainSource Financial Group Announces
                    Exercise of Over-Allotment Option for its
                           Common Stock - NASDAQ, MSFG

MainSource  Financial  Group,  Inc.  (NASDAQ:  MSFG)  announced  today  that the
underwriters  of its recently  completed  public offering have exercised in full
their  over-allotment  option to purchase an additional 260,860 shares of common
stock at a price to the public of $17.50 per share. The issuance and sale of the
additional  shares closed on July 8, 2005.  Combined with the earlier sale,  the
net  proceeds  from  the  offering  are  estimated  to be $32.9  million  before
expenses.  Most,  if not all, of the proceeds of the offering are intended to be
used in the  consummation  of the merger of The Madison  Bank and Trust  Company
with MainSource Bank, the wholly-owned subsidiary of the company.

A  registration  statement  relating  to these  securities  was  filed  with and
declared  effective by the  Securities  and Exchange  Commission.  A copy of the
prospectus  relating to the  offering may be obtained  from  Stifel,  Nicolaus &
Company, Incorporated, 501 North Broadway, 9th Floor, St. Louis, Missouri 63102.
This press release shall not constitute an offer to sell or the  solicitation of
an offer to buy any securities,  nor shall there be any sale or any solicitation
of an offer to buy any securities in any jurisdiction in which such offer,  sale
or solicitation  would be unlawful prior to registration or qualification  under
the securities laws of such jurisdiction.

MainSource  Financial  Group,  Inc.,  headquartered in Greensburg,  Indiana,  is
listed on the  Nasdaq  National  Market  (under  the  symbol:  "MSFG")  and is a
community-focused,  financial holding company with assets of approximately  $1.5
billion.  The Company operates 53 offices in 22 Indiana counties and six offices
in three Illinois  counties through its three banking  subsidiaries,  MainSource
Bank,  Greensburg,   Indiana;   Peoples  Trust  Company,  Linton,  Indiana;  and
MainSource  Bank  of  Illinois,  Kankakee,  Illinois.  Through  its  non-banking
subsidiaries,  MainSource  Insurance LLC,  MainSource  Title LLC, and MainSource
Mortgage LLC, the company  provides various related  financial  services through
the company's banking affiliates.

Forward-Looking Statements

The discussion in this press release includes certain forward-looking statements
based upon management expectations.  Factors which could cause future results to
differ from these expectations include the following: general economic or market
conditions; legislative and regulatory initiatives; monetary and fiscal policies
of the federal  government;  and changes in the company's financial condition or
business prospects.