Myeloperoxidase (MPO), a heme protein expressed by polymorphonuclear leukocytes, generates potent oxidants which are proposed to contribute to tissue damage during inflammation and certain pathogenesis such as neurodegenerative disorders. In this study, twenty omega-[2-oxo-3H-benzoxazol-3-yl]-N-phenylacetamide and propionamide derivatives having substituents of different lipophilic and electronic nature on the N-phenyl ring were synthesized to evaluate the inhibitory effects on in vitro leukocyte MPO chlorinating activity. The most active compounds in the series were the derivatives bearing 2-methyl and 4-nitro substituent on the N-phenyl ring.