Aim: To explore the antibacterial spectrum of ozenoxacin and compare its in vitro activity with that of other antibacterial agents. Materials & methods: In 2010, 10,054 isolates were collected from 128 centers worldwide. Minimum inhibitory concentrations against Gram-positive and Gram-negative isolates were determined for 23 and 13 antibacterial agents, respectively. Results: Ozenoxacin exhibited high in vitro activity against susceptible, and methicillin- or levofloxacin-resistant, Gram-positive bacteria. Ozenoxacin was one or two dilutions less active against Enterobacteriaceae isolates, except for Escherichia coli, than other quinolones. Conclusion: Ozenoxacin is a potent antimicrobial agent mainly against susceptible and resistant strains of Gram-positive isolates (staphylococci and streptococci), and shows activity against some Gram-negative isolates.