The in vitro activity of fleroxacin was compared to that of ciprofloxacin, ofloxacin and three broad-spectrum beta-lactams against 159 clinical isolates using the E-Test. Fleroxacin, ciprofloxacin, and ofloxacin were all active against Enterobacteriaceae with 93, 98 and 94% susceptibility, respectively. For other gram-negative strains, 81% were susceptible to fleroxacin and ofloxacin and 98% to ciprofloxacin. With regard to gram-positive strains, 72% were susceptible to fleroxacin, 83% to ciprofloxacin and 78% to ofloxacin. The broad antibacterial activity suggests that fleroxacin may be an alternative in the treatment of various infections, particularly in light of its favorable pharmacokinetics.