Minimal inhibitory concentrations of 17 antibacterial agents for 34 Moraxella strains were determined using a plate dilution method. A strain of M. nonliquefaciens was found which produced .beta.-lactamase and was resistant to ampicillin and carbenicillin but not to cephalothin. Several strains were relatively resistant to erythromycin and sulfisoxazole. Disk sensitivity tests could be used to reliably predict penicillin and erythromycin resistance but not sulfisoxazole resistance.