We tested 53 clinical isolates of Branhamella catarrhalis recovered from patients with respiratory symptoms to determine the susceptibility of the isolates to 25 antimicrobial agents, including the newer beta-lactam antibiotics. Of the 53 strains, 46 (86.7%) were beta-lactamase producers. All the strains were susceptible to the majority of the new penicillins and cephalosporins. The combinations of amoxacillin-clavulanic acid and ticarcillin-clavulanic acid were also very active against the beta-lactamase-producing strains.