The activity of clinafloxacin was compared to that of ciprofloxacin against 154 Acinetobacter baumannii strains isolated from patients treated in Intensive Care Units. Minimum inhibitory concentrations (MICs) were determined by the Epsilometer test method. The majority (87.6%) of the A. baumannii strains tested were resistant to ciprofloxacin (MIC range 0.125->32, MIC50 = >32, MIC90 = >32). On the contrary, only 9.7% of the strains tested were resistant to clinafloxacin (MIC range 0.023->4, MIC50 = 0.75, MIC90 = 2). Due to its superior activity shown against A. baumannii strains, compared to ciprofloxacin, clinafloxacin may be added to the therapeutic armamentarium for hospital-acquired infections caused by A. baumannii in Intensive Care Units.