Thirty Pasteurella multocida strains were tested against 19 antibiotics using an agar dilution method. Penicillin G was the single most active agent tested. Anti-staphylococcal penicillins were markedly less inhibitory than penicillin G. Other penicillins including phenoxymethyl penicillin, and tetracyclines, chloramphenicol and cephalosporins all inhibited the organisms in low concentrations. Erythromycin and lincomycins had poor activity against several of the strains. The range of M.I.C.s observed for most antibiotics was narrow but wide variation was seen in zone size when antibiotic disk tests were performed.