A total of 2081 adult patients with community-acquired lower respiratory tract infections participated in Phase III clinical trials of sparfloxacin. A total of 1040 patients were randomised to sparfloxacin and 1041 patients received a comparator regimen. Sparfloxacin was administered as a 400 mg loading dose on day 1 followed by 200 mg once daily to patients with community-acquired pneumonia and as a 200 mg loading dose on day 1 followed by 100 mg daily to patients with acute exacerbations of chronic obstructive pulmonary disease. Comparator regimens were amoxycillin/clavulanic acid 500/125 mg tid, amoxycillin 1000 mg tid, a combination of amoxycillin 1000 mg tid plus ofloxacin 200 mg bid or erythromycin 1000 mg bid. The incidence of adverse events, the incidence and severity of antibacterial-related adverse events and the incidence of antibacterial discontinuation due to adverse events were no different among patients treated with sparfloxacin compared with those who received a comparator antibacterial agent. Sparfloxacin appears to be as well tolerated as other oral antibacterial regimens commonly used to treat lower respiratory tract infections.