<PAGE>

     As filed with the Securities and Exchange Commission on June 9, 2000.

                                                      Registration No. _________

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

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                        UNDER THE SECURITIES ACT OF 1933

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

                            OLD SECOND BANCORP, INC.
             ------------------------------------------------------
             (Exact name of Registrant as Specified in its Charter)

<TABLE>

<S>                                     <C>                                           <C>
           DELAWARE                                     522110                            36-3143493
-------------------------------         -------------------------------------         -------------------
(State or other jurisdiction of                    (Primary Standard                   (I.R.S. Employer
incorporation or organization)          Industrial Classification Code Number)        Identification No.)
</TABLE>

                              37 SOUTH RIVER STREET
                             AURORA, ILLINOIS 60506
                                 (630) 892-0202
               ---------------------------------------------------
               (Address, including Zip Code, and Telephone Number,
        including Area Code, of Registrant's Principal Executive Offices)


                            OLD SECOND BANCORP, INC.
                     EMPLOYEES 401(K) SAVINGS PLAN AND TRUST
                     ---------------------------------------
                            (Full title of the plan)

                                 ROBERT DICOSOLA
                            OLD SECOND BANCORP, INC.
                              37 SOUTH RIVER STREET
                             AURORA, ILLINOIS 60506
                                 (630) 892-0202
            ---------------------------------------------------------
            (Name, Address, including Zip Code, and Telephone Number,
                   including Area Code, of Agent for Service)

                                   Copies to:

                              TERESA M. LEVY, ESQ.
                          MICHAEL BEST & FRIEDRICH LLP
                            100 EAST WISCONSIN AVENUE
                                   SUITE 3300
                           MILWAUKEE, WISCONSIN 53202

If any of the securities being registered on this Form S-8 are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, as amended, check the following box. / /



                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
===========================================================================================================
          TITLE OF                                      PROPOSED             PROPOSED
         SECURITIES                                      MAXIMUM              MAXIMUM            AMOUNT OF
            TO BE             AMOUNT TO BE           OFFERING PRICE          AGGREGATE         REGISTRATION
         REGISTERED         REGISTERED(1)(2)          PER SHARE(3)          OFFERING(3)             FEE
-----------------------------------------------------------------------------------------------------------
<S>                         <C>                      <C>                    <C>                <C>
        Common Stock
       $1.00 par value             60,000                $21.56             $1,293,600            $341.51
          per share

-----------------------------------------------------------------------------------------------------------
</TABLE>

         (1)      Represents 60,000 shares reserved for issuance under the Old
                  Second Bancorp, Inc. Employees 401(k) Savings Plan and Trust
                  (the "Plan").

         (2)      Pursuant to Rule 416(c) under the Securities Act of 1933, as
                  amended (the "Securities Act"), this Registration Statement
                  covers an indeterminate amount of interests to be offered or
                  sold pursuant to the Plan (including any interests in the Plan
                  trust) described herein.

         (3)      Estimated solely for the purpose of determining the
                  registration fee pursuant to Rule 457(h)(1). The proposed
                  maximum offering price per share is based upon the average of
                  the high and low prices for the shares of Common Stock as
                  reported on the NASDAQ National Market System on June 5, 2000.

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

         This Registration Statement shall become effective automatically upon
the date of filing in accordance with Section 8(a) of the Securities Act, and 17
C.F.R. Section 230.462.



                             Total Number of Pages: 8
                             Exhibit Index on Page: 8

================================================================================
<PAGE>

          PART I. INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

         The information required by Part I will be included in documents
sent or given to participants in Old Second Bancorp, Inc. Employees 401(k)
Savings Plan and Trust (the "Plan"). Such documents are not being filed with
the Securities and Exchange Commission (the "Commission") either as part of
this Registration Statement or as prospectuses or prospectus supplements
pursuant to Rule 424 in reliance on Rule 428.

          PART II. INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

         ITEM 3.   INCORPORATION OF DOCUMENTS BY REFERENCE.

                   The following  documents filed by Old Second Bancorp,
Inc. (the "Company" or "Registrant")  with the Commission are incorporated
herein by reference and made a part hereof:

         (a)      The Company's latest Annual Report on Form 10-K for the year
                  ended December 31, 1999, which includes the consolidated
                  financial statements of the Company as of December 31, 1999,
                  1998 and 1997, the related consolidated statements of income,
                  changes in stockholders' equity and cash flows for each of the
                  three years in the period ended December 31, 1999, and the
                  consolidated balance sheets at December 31, 1999 and 1998,
                  together with the related notes and Report of Independent
                  Auditors of the Company (dated January 28, 2000).

         (b)      All other reports filed pursuant to Section 13 or 15(d) of the
                  Securities Exchange Act of 1934, as amended (the "Exchange
                  Act"), since the end of the last fiscal year for which
                  financial statements were included in the report referred to
                  in (a) above.

         (c)      The description of the Company's Common Stock included in
                  Amendment No. 1 to the Form S-14 Registration Statement filed
                  with the Commission on January 22, 1982 (File No. 2-75587).

                  All documents filed by the Company pursuant to Sections
13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the filing of a
post-effective amendment which indicates that all securities offered hereby
have been sold or which deregisters all securities remaining unsold, shall be
deemed to be incorporated by reference herein and to be a part hereof from
the date of the filing of such documents.

         ITEM 4.  DESCRIPTION OF SECURITIES.

                  Not Applicable.


         ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

                  Not Applicable.

                                    -2-

<PAGE>

         ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

                  Reference is made to Section 102(b)(7) of the Delaware
General Corporation Law (the "DGCL"), which enables a corporation in its
original certificate of incorporation or an amendment thereto to eliminate or
limit the personal liability of a director to the corporation or its
stockholders for monetary damages for breach of the director's fiduciary
duty, except (i) for any breach of the director's duty of loyalty to the
corporation or its stockholders, (ii) for acts or omissions not in good faith
or which involve intentional misconduct or a knowing violation of law, (iii)
pursuant to Section 174 of the DGCL (providing for liability of directors for
unlawful payment of dividends or unlawful stock purchases or redemptions), or
(iv) or any transaction from which the director derived an improper personal
benefit. The Company's Restated Certificate includes a provision limiting the
liability of directors consistent with Section 102(b)(7) of the DGCL.

                  Reference also is made to Section 145 of the DGCL which
provides that a corporation may indemnify any person, including officers and
directors, who is, or is threatened to be made, a party to any threatened,
pending or completed legal action, suit or proceeding, whether civil,
criminal, administrative or investigative (other than an action by or in the
right of such corporation), by reason of the fact that such person is or was
an officer, director, employee or agent of such corporation, or is or was
serving at the request of such corporation as a director, officer, employee
or agent of another corporation or enterprise. The indemnity may include
expenses (including attorney's fees), judgments, fines and amounts paid in
settlement actually and reasonably incurred by such person in connection with
such action, suit or proceeding, if such person acted in good faith and in a
manner he reasonably believed to be in or not opposed to the corporation's
best interests and, with respect to any criminal proceeding, had no
reasonable cause to believe that his conduct was unlawful. A Delaware
corporation may indemnify its officers, directors, employees and agents in an
action by or in the right of the corporation under the same conditions,
except that no indemnification is permitted without judicial approval if the
officer, director, employee or agent is adjudged to be liable to the
corporation. Where an officer, director, employee or agent is successful on
the merits or otherwise in the defense of any action referred to above, the
corporation must indemnify him against the expenses which such officer,
director, employee or agent actually and reasonable incurred in connection
therewith. The Company's Restated Certificate provides for indemnification of
directors and officers of the Company to the full extent permitted by the
DGCL.

                  The Company maintains a director's and officer's liability
policy to insure its liability under the above-described provision of its
Restated Certificate and to insure individual directors and officers against
certain obligations not covered by such provisions.

         ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.

                  Not Applicable.

         ITEM 8.  EXHIBITS.

                  The Exhibits to this Registration Statement are listed in
the Exhibit Index on page 9 of this Registration Statement, which Exhibit
Index is incorporated herein by reference.

         ITEM 9.  UNDERTAKINGS.

         The undersigned Registrant hereby undertakes as follows:

         (1)      To file, during any period in which offers or sales are
                  being made, a post-effective amendment to this Registration
                  Statement 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.

         (2)      For the purpose of determining any liability under the
                  Securities Act, 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.

                                    -3-

<PAGE>

         (3)      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.

         (4)      For purposes of determining any liability under the Securities
                  Act, each filing of the Registrant's or the Plan's annual
                  report pursuant to Section 13(a) or 15(d) of the Exchange Act
                  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.

         (5)      The Registrant undertakes to deliver or cause to be delivered
                  with the prospectus, if not already delivered, the latest
                  annual report to security holders that is incorporated by
                  reference in the prospectus and furnished to and meeting the
                  requirements of Rule 14a-3 or 14c-3 under the Exchange Act,
                  unless such employee otherwise has received a copy of such
                  report, in which case the Registrant shall state in the
                  prospectus that it will promptly furnish, without charge, a
                  copy of such report on written or oral request of the
                  employee, 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.

         (6)      Insofar as indemnification for liabilities arising under the
                  Securities Act may be permitted to directors, officers and
                  controlling persons of the Registrant pursuant to the
                  foregoing provisions, or otherwise, the Registrant has been
                  advised that in the opinion of the Commission, such
                  indemnification is against public policy as expressed in the
                  Securities 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 Securities Act and will be governed by the
                  final adjudication of such issue.

                                    -4-

<PAGE>

                                   SIGNATURES


         PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, AS
AMENDED, OLD SECOND BANCORP, INC. CERTIFIES THAT IT HAS REASONABLE GROUNDS TO
BELIEVE THAT IT MEETS ALL THE REQUIREMENTS FOR FILING ON FORM S-8 AND HAS
DULY CAUSED THIS REGISTRATION STATEMENT TO BE SIGNED ON ITS BEHALF BY THE
UNDERSIGNED, THEREUNTO DULY AUTHORIZED, IN THE CITY OF AURORA, STATE OF
ILLINOIS ON JUNE 5, 2000.

                           OLD SECOND BANCORP, INC.



                       By: /s/ James E. Benson
                           --------------------------------------
                           James E. Benson, Chairman of the Board


                       By: /s/ William B. Skoglund
                           --------------------------------------
                           William B. Skoglund, President and
                           Chief Executive Officer




                                POWER OF ATTORNEY


                  KNOW ALL MEN BY THESE PRESENTS, that each person whose
signature appears below constitutes and appoints James E. Benson and William B.
Skoglund, and each of them, his true and lawful attorney-in-fact and agent, with
full power of substitution and resubstitution, for him and in his name, place
and stead, in any and all capacities, to sign any and all amendments (including
pre-effective and post-effective amendments) to this registration statement, and
to file the same, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, granting unto said
attorneys-in-fact and agents, and each of them acting singly, full power and
authority to do and perform each and every act and thing necessary and requisite
to be done, as fully and to all intents and purposes as he might or could do in
person, hereby ratifying and confirming all that said attorneys-in-fact and
agents or any of them may lawfully do or cause to be done by virtue hereof.

                                    -5-

<PAGE>

<TABLE>
<CAPTION>

      SIGNATURE                                      TITLE                                DATE
      ---------                                      -----                                ----
<S>                                       <C>                                         <C>
/s/ James E. Benson                       Chairman of the Board and Director          June 5, 2000
-----------------------------
James E. Benson


/s/ William B. Skoglund                   President and Chief Executive Officer       June 5, 2000
-----------------------------
William B. Skoglund


/s/ J. Douglas Cheatham                   Chief Financial Officer (Principal          June 5, 2000
-----------------------------
J. Douglas Cheatham                       Accounting Officer)


/s/ Walter Alexander                      Director                                    June 5, 2000
-----------------------------
Walter Alexander


/s/ Marvin Fagel                          Director                                    June 5, 2000
-----------------------------
Marvin Fagel


/s/ William Kane                          Director                                    June 5, 2000
-----------------------------
William Kane


/s/ Kenneth Lindgren                      Director                                    June 5, 2000
-----------------------------
Kenneth Lindgren


/s/ Jesse Maberry                         Director                                    June 5, 2000
-----------------------------
Jesse Maberry


/s/ D. Chet McKee                         Director                                    June 5, 2000
-----------------------------
D. Chet McKee


                                          Director                                    June 5, 2000
-----------------------------
William Meyer


                                          Director                                    June 5, 2000
-----------------------------
Gary McCarter


/s/ Gerald Palmer                         Director                                    June 5, 2000
-----------------------------
Gerald Palmer


/s/ George Starman III                    Director                                    June 5, 2000
-----------------------------
George Starman III


                                          Director                                    June 5, 2000
-----------------------------
James Schmitz
</TABLE>

                                    -6-

<PAGE>

         PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, AS AMENDED
THE TRUSTEES (OR OTHER PERSONS WHO ADMINISTER THE EMPLOYEE BENEFIT PLAN) HAVE
DULY CAUSED THIS REGISTRATION STATEMENT TO BE SIGNED ON ITS BEHALF BY THE
UNDERSIGNED, THEREUNTO DULY AUTHORIZED, IN THE CITY OF AURORA AND THE STATE OF
ILLINOIS, ON THE 5th DAY OF JUNE 2000.




                                        OLD SECOND BANCORP, INC.
                                        EMPLOYEES 401(K) SAVINGS PLAN AND TRUST:



                                    By: /s/ Robert DiCosola
                                        --------------------------------------
                                        Robert DiCosola
                                        Member, Employee Benefits Committee
                                        (Plan Administrator)

                                     -7-

<PAGE>

                                  EXHIBIT INDEX

<TABLE>
<CAPTION>

                                                                                                 PAGE NUMBER IN
REGULATION S-K                                                                                     SEQUENTIALLY
 EXHIBIT NO.               DESCRIPTION OF DOCUMENT                                                NUMBERED COPY
--------------             -----------------------                                               --------------
<S>                        <C>                                                                   <C>
Exhibit 5                  Opinion of Michael Best & Friedrich LLP..............................


Exhibit 23.1               Consent of Ernst & Young LLP.........................................


Exhibit 23.2               Consent of Michael Best & Friedrich LLP (included in Exhibit 5)......


Exhibit 99                 Internal Revenue Service Determination Letter........................
</TABLE>

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

                                    -8-
[{"type": "S-8", "sequence": "1", "filename": "s-8.txt", "description": "S-8", "secsgml_size_bytes": 22556}]
{"company-data": {"conformed-name": "OLD SECOND BANCORP INC", "cik": "0000357173", "assigned-sic": "6022", "irs-number": "363143493", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-38914", "film-number": "652040"}, "business-address": {"street1": "37 S RIVER ST", "city": "AURORA", "state": "IL", "zip": "60507", "phone": "7088920202"}, "mail-address": {"street1": "37 SOUTH RIVER STREET", "city": "AURORA", "state": "IL", "zip": "60507"}}
As filed with the Securities and Exchange Commission on June 9, 2000.

                                                      Registration No. _________

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

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                        UNDER THE SECURITIES ACT OF 1933

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

                            OLD SECOND BANCORP, INC.
             ------------------------------------------------------
             (Exact name of Registrant as Specified in its Charter)
DELAWARE                                     522110                            36-3143493
-------------------------------         -------------------------------------         -------------------
(State or other jurisdiction of                    (Primary Standard                   (I.R.S. Employer
incorporation or organization)          Industrial Classification Code Number)        Identification No.)
37 SOUTH RIVER STREET
                             AURORA, ILLINOIS 60506
                                 (630) 892-0202
               ---------------------------------------------------
               (Address, including Zip Code, and Telephone Number,
        including Area Code, of Registrant's Principal Executive Offices)

                            OLD SECOND BANCORP, INC.
                     EMPLOYEES 401(K) SAVINGS PLAN AND TRUST
                     ---------------------------------------
                            (Full title of the plan)

                                 ROBERT DICOSOLA
                            OLD SECOND BANCORP, INC.
                              37 SOUTH RIVER STREET
                             AURORA, ILLINOIS 60506
                                 (630) 892-0202
            ---------------------------------------------------------
            (Name, Address, including Zip Code, and Telephone Number,
                   including Area Code, of Agent for Service)

                                   Copies to:

                              TERESA M. LEVY, ESQ.
                          MICHAEL BEST & FRIEDRICH LLP
                            100 EAST WISCONSIN AVENUE
                                   SUITE 3300
                           MILWAUKEE, WISCONSIN 53202

If any of the securities being registered on this Form S-8 are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, as amended, check the following box. / /

                         CALCULATION OF REGISTRATION FEE
===========================================================================================================
          TITLE OF                                      PROPOSED             PROPOSED
         SECURITIES                                      MAXIMUM              MAXIMUM            AMOUNT OF
            TO BE             AMOUNT TO BE           OFFERING PRICE          AGGREGATE         REGISTRATION
         REGISTERED         REGISTERED(1)(2)          PER SHARE(3)          OFFERING(3)             FEE
-----------------------------------------------------------------------------------------------------------
Common Stock
       $1.00 par value             60,000                $21.56             $1,293,600            $341.51
          per share

-----------------------------------------------------------------------------------------------------------
(1)      Represents 60,000 shares reserved for issuance under the Old
                  Second Bancorp, Inc. Employees 401(k) Savings Plan and Trust
                  (the "Plan").

         (2)      Pursuant to Rule 416(c) under the Securities Act of 1933, as
                  amended (the "Securities Act"), this Registration Statement
                  covers an indeterminate amount of interests to be offered or
                  sold pursuant to the Plan (including any interests in the Plan
                  trust) described herein.

         (3)      Estimated solely for the purpose of determining the
                  registration fee pursuant to Rule 457(h)(1). The proposed
                  maximum offering price per share is based upon the average of
                  the high and low prices for the shares of Common Stock as
                  reported on the NASDAQ National Market System on June 5, 2000.

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

         This Registration Statement shall become effective automatically upon
the date of filing in accordance with Section 8(a) of the Securities Act, and 17
C.F.R. Section 230.462.

                             Total Number of Pages: 8
                             Exhibit Index on Page: 8

================================================================================
PART I. INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

         The information required by Part I will be included in documents
sent or given to participants in Old Second Bancorp, Inc. Employees 401(k)
Savings Plan and Trust (the "Plan"). Such documents are not being filed with
the Securities and Exchange Commission (the "Commission") either as part of
this Registration Statement or as prospectuses or prospectus supplements
pursuant to Rule 424 in reliance on Rule 428.

          PART II. INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

         ITEM 3.   INCORPORATION OF DOCUMENTS BY REFERENCE.

                   The following  documents filed by Old Second Bancorp,
Inc. (the "Company" or "Registrant")  with the Commission are incorporated
herein by reference and made a part hereof:

         (a)      The Company's latest Annual Report on Form 10-K for the year
                  ended December 31, 1999, which includes the consolidated
                  financial statements of the Company as of December 31, 1999,
                  1998 and 1997, the related consolidated statements of income,
                  changes in stockholders' equity and cash flows for each of the
                  three years in the period ended December 31, 1999, and the
                  consolidated balance sheets at December 31, 1999 and 1998,
                  together with the related notes and Report of Independent
                  Auditors of the Company (dated January 28, 2000).

         (b)      All other reports filed pursuant to Section 13 or 15(d) of the
                  Securities Exchange Act of 1934, as amended (the "Exchange
                  Act"), since the end of the last fiscal year for which
                  financial statements were included in the report referred to
                  in (a) above.

         (c)      The description of the Company's Common Stock included in
                  Amendment No. 1 to the Form S-14 Registration Statement filed
                  with the Commission on January 22, 1982 (File No. 2-75587).

                  All documents filed by the Company pursuant to Sections
13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the filing of a
post-effective amendment which indicates that all securities offered hereby
have been sold or which deregisters all securities remaining unsold, shall be
deemed to be incorporated by reference herein and to be a part hereof from
the date of the filing of such documents.

         ITEM 4.  DESCRIPTION OF SECURITIES.

                  Not Applicable.

         ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

                  Not Applicable.

                                    -2-
ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

                  Reference is made to Section 102(b)(7) of the Delaware
General Corporation Law (the "DGCL"), which enables a corporation in its
original certificate of incorporation or an amendment thereto to eliminate or
limit the personal liability of a director to the corporation or its
stockholders for monetary damages for breach of the director's fiduciary
duty, except (i) for any breach of the director's duty of loyalty to the
corporation or its stockholders, (ii) for acts or omissions not in good faith
or which involve intentional misconduct or a knowing violation of law, (iii)
pursuant to Section 174 of the DGCL (providing for liability of directors for
unlawful payment of dividends or unlawful stock purchases or redemptions), or
(iv) or any transaction from which the director derived an improper personal
benefit. The Company's Restated Certificate includes a provision limiting the
liability of directors consistent with Section 102(b)(7) of the DGCL.

                  Reference also is made to Section 145 of the DGCL which
provides that a corporation may indemnify any person, including officers and
directors, who is, or is threatened to be made, a party to any threatened,
pending or completed legal action, suit or proceeding, whether civil,
criminal, administrative or investigative (other than an action by or in the
right of such corporation), by reason of the fact that such person is or was
an officer, director, employee or agent of such corporation, or is or was
serving at the request of such corporation as a director, officer, employee
or agent of another corporation or enterprise. The indemnity may include
expenses (including attorney's fees), judgments, fines and amounts paid in
settlement actually and reasonably incurred by such person in connection with
such action, suit or proceeding, if such person acted in good faith and in a
manner he reasonably believed to be in or not opposed to the corporation's
best interests and, with respect to any criminal proceeding, had no
reasonable cause to believe that his conduct was unlawful. A Delaware
corporation may indemnify its officers, directors, employees and agents in an
action by or in the right of the corporation under the same conditions,
except that no indemnification is permitted without judicial approval if the
officer, director, employee or agent is adjudged to be liable to the
corporation. Where an officer, director, employee or agent is successful on
the merits or otherwise in the defense of any action referred to above, the
corporation must indemnify him against the expenses which such officer,
director, employee or agent actually and reasonable incurred in connection
therewith. The Company's Restated Certificate provides for indemnification of
directors and officers of the Company to the full extent permitted by the
DGCL.

                  The Company maintains a director's and officer's liability
policy to insure its liability under the above-described provision of its
Restated Certificate and to insure individual directors and officers against
certain obligations not covered by such provisions.

         ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.

                  Not Applicable.

         ITEM 8.  EXHIBITS.

                  The Exhibits to this Registration Statement are listed in
the Exhibit Index on page 9 of this Registration Statement, which Exhibit
Index is incorporated herein by reference.

         ITEM 9.  UNDERTAKINGS.

         The undersigned Registrant hereby undertakes as follows:

         (1)      To file, during any period in which offers or sales are
                  being made, a post-effective amendment to this Registration
                  Statement 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.

         (2)      For the purpose of determining any liability under the
                  Securities Act, 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.

                                    -3-
(3)      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.

         (4)      For purposes of determining any liability under the Securities
                  Act, each filing of the Registrant's or the Plan's annual
                  report pursuant to Section 13(a) or 15(d) of the Exchange Act
                  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.

         (5)      The Registrant undertakes to deliver or cause to be delivered
                  with the prospectus, if not already delivered, the latest
                  annual report to security holders that is incorporated by
                  reference in the prospectus and furnished to and meeting the
                  requirements of Rule 14a-3 or 14c-3 under the Exchange Act,
                  unless such employee otherwise has received a copy of such
                  report, in which case the Registrant shall state in the
                  prospectus that it will promptly furnish, without charge, a
                  copy of such report on written or oral request of the
                  employee, 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.

         (6)      Insofar as indemnification for liabilities arising under the
                  Securities Act may be permitted to directors, officers and
                  controlling persons of the Registrant pursuant to the
                  foregoing provisions, or otherwise, the Registrant has been
                  advised that in the opinion of the Commission, such
                  indemnification is against public policy as expressed in the
                  Securities 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 Securities Act and will be governed by the
                  final adjudication of such issue.

                                    -4-
SIGNATURES

         PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, AS
AMENDED, OLD SECOND BANCORP, INC. CERTIFIES THAT IT HAS REASONABLE GROUNDS TO
BELIEVE THAT IT MEETS ALL THE REQUIREMENTS FOR FILING ON FORM S-8 AND HAS
DULY CAUSED THIS REGISTRATION STATEMENT TO BE SIGNED ON ITS BEHALF BY THE
UNDERSIGNED, THEREUNTO DULY AUTHORIZED, IN THE CITY OF AURORA, STATE OF
ILLINOIS ON JUNE 5, 2000.

                           OLD SECOND BANCORP, INC.

                       By: /s/ James E. Benson
                           --------------------------------------
                           James E. Benson, Chairman of the Board

                       By: /s/ William B. Skoglund
                           --------------------------------------
                           William B. Skoglund, President and
                           Chief Executive Officer

                                POWER OF ATTORNEY

                  KNOW ALL MEN BY THESE PRESENTS, that each person whose
signature appears below constitutes and appoints James E. Benson and William B.
Skoglund, and each of them, his true and lawful attorney-in-fact and agent, with
full power of substitution and resubstitution, for him and in his name, place
and stead, in any and all capacities, to sign any and all amendments (including
pre-effective and post-effective amendments) to this registration statement, and
to file the same, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, granting unto said
attorneys-in-fact and agents, and each of them acting singly, full power and
authority to do and perform each and every act and thing necessary and requisite
to be done, as fully and to all intents and purposes as he might or could do in
person, hereby ratifying and confirming all that said attorneys-in-fact and
agents or any of them may lawfully do or cause to be done by virtue hereof.

                                    -5-
SIGNATURE                                      TITLE                                DATE
      ---------                                      -----                                ----
/s/ James E. Benson                       Chairman of the Board and Director          June 5, 2000
-----------------------------
James E. Benson

/s/ William B. Skoglund                   President and Chief Executive Officer       June 5, 2000
-----------------------------
William B. Skoglund

/s/ J. Douglas Cheatham                   Chief Financial Officer (Principal          June 5, 2000
-----------------------------
J. Douglas Cheatham                       Accounting Officer)

/s/ Walter Alexander                      Director                                    June 5, 2000
-----------------------------
Walter Alexander

/s/ Marvin Fagel                          Director                                    June 5, 2000
-----------------------------
Marvin Fagel

/s/ William Kane                          Director                                    June 5, 2000
-----------------------------
William Kane

/s/ Kenneth Lindgren                      Director                                    June 5, 2000
-----------------------------
Kenneth Lindgren

/s/ Jesse Maberry                         Director                                    June 5, 2000
-----------------------------
Jesse Maberry

/s/ D. Chet McKee                         Director                                    June 5, 2000
-----------------------------
D. Chet McKee

                                          Director                                    June 5, 2000
-----------------------------
William Meyer

                                          Director                                    June 5, 2000
-----------------------------
Gary McCarter

/s/ Gerald Palmer                         Director                                    June 5, 2000
-----------------------------
Gerald Palmer

/s/ George Starman III                    Director                                    June 5, 2000
-----------------------------
George Starman III

                                          Director                                    June 5, 2000
-----------------------------
James Schmitz
-6-
PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, AS AMENDED
THE TRUSTEES (OR OTHER PERSONS WHO ADMINISTER THE EMPLOYEE BENEFIT PLAN) HAVE
DULY CAUSED THIS REGISTRATION STATEMENT TO BE SIGNED ON ITS BEHALF BY THE
UNDERSIGNED, THEREUNTO DULY AUTHORIZED, IN THE CITY OF AURORA AND THE STATE OF
ILLINOIS, ON THE 5th DAY OF JUNE 2000.

                                        OLD SECOND BANCORP, INC.
                                        EMPLOYEES 401(K) SAVINGS PLAN AND TRUST:

                                    By: /s/ Robert DiCosola
                                        --------------------------------------
                                        Robert DiCosola
                                        Member, Employee Benefits Committee
                                        (Plan Administrator)

                                     -7-
EXHIBIT INDEX
PAGE NUMBER IN
REGULATION S-K                                                                                     SEQUENTIALLY
 EXHIBIT NO.               DESCRIPTION OF DOCUMENT                                                NUMBERED COPY
--------------             -----------------------                                               --------------
Exhibit 5                  Opinion of Michael Best & Friedrich LLP..............................

Exhibit 23.1               Consent of Ernst & Young LLP.........................................

Exhibit 23.2               Consent of Michael Best & Friedrich LLP (included in Exhibit 5)......

Exhibit 99                 Internal Revenue Service Determination Letter........................
---------------

                                    -8-