Gemifloxacin, a new fluoroquinolone with enhanced activity against gram-positive aerobes, was compared to ciprofloxacin, levofloxacin and ofloxacin against 21,464 recent isolates from 16 European countries. Gemifloxacin was the most potent fluoroquinolone against streptococci including penicillin-, macrolide- and ciprofloxacin-resistant Streptococcus pneumoniae, Staphylococcus aureus, coagulase-negative staphylococci, Acinetobacter spp., Haemophilus spp. and Moraxella catarrhalis. This drug was more potent than or comparable to ciprofloxacin against members of the family Enterobacteriaceae, Burkholderia cepacia, Pseudomonas aeruginosa and Stenotrophomonas maltophilia. Gemifloxacin is a promising fluoroquinolone with potent in vitro activity.