EXHIBIT 4(a) PEOPLES BANCORP INC. 138 Putnam Street Marietta, OH 45750 (740) 373-3155 March 13, 2006 Securities and Exchange Commission Judiciary Plaza 450 Fifth Street, N.W. Washington, D.C. 20549 RE: Peoples Bancorp Inc. - Form 10-K for the fiscal year ended December 31, 2005 Ladies and Gentlemen: Peoples Bancorp Inc., an Ohio corporation, is today filing its Annual Report on Form 10-K for the fiscal year ended December 31, 2005 (the "Form 10-K"), as executed on March 7, 2006. Pursuant to the provisions of Item 601(b)(4)(iii) of Regulation S-K, Peoples Bancorp Inc. hereby agrees to furnish to the Commission, upon request, copies of instruments and agreements defining the rights of holders of Peoples Bancorp Inc.'s long-term debt and of the long-term debt of its consolidated subsidiaries, not being filed with or incorporated by reference in the Form 10-K. Such long-term debt does not exceed 10% of the total assets of Peoples Bancorp Inc. and its subsidiaries on a consolidated basis. Very truly yours, Peoples Bancorp Inc. /s/ DONALD J. LANDERS Donald J. Landers Director of Finance and Chief Accounting Officer