Cencora (COR) 10-Q 2004 Q2 Quarterly report

Exhibit 32.1

Section 1350 Certification of Chief Executive Officer

In connection with the Quarterly Report of AmerisourceBergen Corporation (the “Company”) on Form 10-Q for the fiscal quarter ended March 31, 2004 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, R. David Yost, Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

(1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ R. David Yost

R. David Yost

Chief Executive Officer

May 12, 2004