The in vitro activity of sparfloxacin, a new fluoroquinolone, was compared with ciprofloxacin and ofloxacin against 166 consecutive isolates from the upper respiratory tract of outpatients. The strains were fully susceptible to three quinolones. The antibacterial activity of sparfloxacin was comparable or better than that of ofloxacin and ciprofloxacin against all strains. Sparfloxacin was fourfold more active against Staphylococcus aureus and Streptococcus pneumoniae. The favourable MIC values and a prolonged half-life makes sparfloxacin interesting for treating respiratory tract infections in out-patient care.