Exhibit 32.1

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO SECTION 906 OF THE
SARBANES-OXLEY ACT OF 2002

Pursuant to section 906 of the Sarbanes-Oxley Act of 2002 (subsections (a) and (b) of section 1350, chapter 63 of Title 18, United States Code), the undersigned officer of NeoPharm, Inc., a Delaware corporation (the “Company”), does hereby certify with respect to the Quarterly Report of the Company on Form 10-Q for the quarter ended March 31, 2006 as filed with the Securities and Exchange Commission (the “10-Q Report”) that:

(1)the 10-Q 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 10-Q Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated: May 15, 2006	/s/ Guillermo A. Herrera
	Guillermo A. Herrera
	Chief Executive Officer