The efficacy and safety of levofloxacin for the treatment of community-acquired pneumonia (CAP) was evaluated in 264 patients who exhibited infiltrates on chest roentgenograms and clinical signs and symptoms of CAP in an open-label trial. Patients were treated with levofloxacin 500 mg orally or intravenously once daily for 7–14 days. Of the 264 patients, 156 were outpatients; of the 108 inpatients, 40 (15%) met the criteria for severe pneumonia. Of the 136 microbiologically evaluable patients, 79 had a single “typical” pathogen, 31 had a single atypical pathogen, 1 7 had both typical and atypical pathogens 19 had two or more typical pathogens. The most common pathogens (along with eradication rates) were: Haemophilus influenzae (97.4%), Streptococcus pneumoniae (97.1%) Chlamydia pneumoniae (95.7%). Eradication rates were 94.1% for patients with mild to moderate infections and 97.1% for those with severe infections. Of the 234 clinically evaluable patients, the overall clinical success rate was 95% (78% cured and 17% improved). The most common drug-related adverse events were diarrhea (1.5%) and nausea (1.1%). Results suggest that, regardless of the number of pathogens and the severity of pneumonia, levofloxacin 500 mg once daily, intravenously or orally, achieved an overall excellent eradication/clinical success rate with minimal side effects. Levofloxacin thus warrants consideration as initial monotherapy for CAP.