Peptide-based alpha-ketoamides, alpha-ketoesters and alpha-diketones were designed, synthesized and evaluated against HCV NS3 protease. alpha-Ketoamides have the highest affinity among the three classes, with 8 being the most potent inhibitor with an IC50 Of 340 nM. (C) 2000 DuPont Pharmaceuticals Company. Published by Elsevier Science Ltd. All rights reserved.