Synthesis and biological properties of a novel class of cephalosporins with a 2-[5-(3-hydroxy-4 pyridon-6-yl)1,3,4-oxadiazol-2-yl]thioethyl group at C-7 position are described. Among them, the compounds having a pyridiniumthiomethyl group at C-3 position were found to possess high in vitro potency and showed excellent in vivo efficacy against both S. aureus and P. aeruginosa.