Fleroxacin, a new quinolone antimicrobial agent, was evaluated as part of a multicenter, comparative, open-label, randomized trial with ceftazidime in the treatment of lower respiratory tract infections and skin and soft-tissue infections. After written informed consent was obtained, 20 patients were entered at our center. Twelve patients were assigned to the fleroxacin group; 6 in each infection category. Of these 12 patients, 2 with pneumonia and 3 with skin and soft-tissue infection were not clinically evaluable. The mean duration of therapy was 5.7 +/- 3.0 days in the fleroxacin group versus 7.9 +/- 2.0 days in the ceftazidime group. The gram-positive organisms responsible for those infections not evaluable were methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae, and group F streptococcus, all of which were resistant to fleroxacin. In total, 6 gram-positive isolates were resistant to fleroxacin. All but 2 S aureus isolates were susceptible to ceftazidime. Adverse reactions in both groups were negligible. Fleroxacin was found to be as effective as ceftazidime against a variety of gram-negative pathogens, but local susceptibility patterns for quinolones should be checked before empiric use of fleroxacin against gram-positive pathogens such as streptococci.