The efficacy and safety of grepafloxacin in treating patients with community-acquired pneumonia (CAP) was assessed in an open-label, noncomparative study. Patients (N = 273) received grepafloxacin 600 mg QD for 10 days. A total of 237 patients (87%) completed the study. In assessable patients, the clinical success rate at follow-up (4 to 6 weeks after the last dose) was 89% (211/238 patients). In microbiologically assessable patients, the eradication rate at follow-up was 95% (86/91 isolates). Grepafloxacin was highly effective in the treatment of bacterial CAP caused by Streptococcus pneumoniae (irrespective of penicillin susceptibility), Haemophilus influenzae, Haemophilus parainfluenzae, Moraxella catarrhalis, and Staphylococcus aureus and in the therapy of atypical pneumonia caused by Mycoplasma pneumoniae and Legionella pneumophila. Grepafloxacin was well tolerated, with the most frequently reported drug-related adverse events being taste perversion and nausea. Grepafloxacin 600 mg QD for 10 days was highly effective and well tolerated in the treatment of patients with CAP.