8-K

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C.  20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of

the Securities Exchange Act of 1934

Date of Report	September 19, 2007
(Date of earliest event reported)	September 19, 2007

Old Second Bancorp, Inc.

(Exact name of Registrant as specified in its charter)

Delaware

(State or other jurisdiction of incorporation)

0-10537	36-3143493
(Commission File Number)	(I.R.S. Employer Identification Number)
37 South River Street, Aurora, Illinois	60507
(Address of principal executive offices)	(Zip Code)

(630) 892-0202

(Registrant’s telephone number, including area code)

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2 below):

o  Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o  Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o  Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o  Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 5.04 Temporary Suspension of Trading Under Registrant’s Employee Benefit Plans

On September 19, 2007, Old Second Bancorp, Inc. (“Old Second”) sent a notice to its directors and executive officers informing them that a blackout period is expected to begin on October 8, 2007 and will continue until the week of November 5, 2007.  The blackout period is a result of a change in administrators for the Old Second Bancorp, Inc. Employees’ 401(k) Plan.  The blackout period restricts directors and executive officers from, directly or indirectly, purchasing, selling or otherwise acquiring or transferring certain equity securities of Old Second.  The notice was provided to Old Second’s directors and executive officers in accordance with Section 306 the Sarbanes-Oxley Act of 2002 and Rule 104 of Regulation BTR.

A copy of the notice is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits

(d)  Exhibits

99.1         Form of notice dated September 19, 2007

SIGNATURES

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.

		OLD SECOND BANCORP, INC.
Dated: September 19, 2007	By:	/s/ J. Douglas Cheatham
		J. Douglas Cheatham
		Executive Vice President
		and Chief Financial Officer

2

EX-99.1

Exhibit 99.1

IMPORTANT NOTICE CONCERNING YOUR RIGHTS

REGARDING OLD SECOND BANCORP, INC. STOCK

September 19, 2007

As a director or executive officer of Old Second Bancorp, Inc. (“Old Second”) you are subject to the restrictions under Section 306(a) of the Sarbanes-Oxley Act of 2002 (the “Act”), which prohibits certain trades during employee benefit plan blackout periods.

1.This notice is to inform you that as a director or executive officer of Old Second, you will be unable to, either directly or indirectly, purchase, sell or otherwise acquire or transfer any of your Old Second stock that you acquired in connection with your services or employment as a director or executive officer, due to a blackout period under the Old Second Bancorp, Inc. Employees’ 401(k) Plan (the “Plan”).

2.The Plan’s blackout period is a result of a change in the Plan’s recordkeeping systems.  Accordingly, a concurrent restriction on trading by all directors and executive officers under Section 306(a) of the Act will apply.

3.The blackout period will specifically apply to Old Second stock.

4.The blackout period for the Plan is expected to begin on October 8, 2007 and end during the week of November 5, 2007.  During these weeks, you can determine whether the blackout period has started or ended by accessing the following website: http://oldsecond.com/Careers/BlackOut/401KBlackoutNotice.pdf.

5.During the blackout period, you will be prohibited from, directly or indirectly, purchasing, selling or otherwise acquiring or transferring any equity securities of Old Second(or derivative securities of those equity securities, such as stock options) during the Plan blackout period.  The prohibition on transactions by you applies both to amounts, if any, you may have invested in Old Second stock under the Plan and to Old Second stock you hold outside of the Plan.  This prohibition also applies to any direct or indirect pecuniary interest you may have in such securities, such as Old Second stock held by immediate family members living with you, or held in trust, or by controlled partnerships or corporations.  The prohibition on purchases, sales and other transactions does not apply to trades made pursuant to Rule 10b5-1 trading plans, provided that you did not enter into or modify the trading plan during the blackout period, or while aware of the actual or approximate beginning or ending dates of the blackout period.

6.If you have any questions regarding the blackout period, you should contact:

Bob DiCosola, Executive Vice President of Human Resources

Old Second Bancorp, Inc., 37 South River Street, Aurora, Illinois  60506

Phone: 630-906-5546.  Email: rdicosola@oldsecond.com