The objective of this randomized, double-blind, multicenter study of 329 adult patients requiring hospitalization was to compare the safety and efficacy of sparfloxacin at a dosage of 200 mg once daily (following a 400-mg loading dose on day 1) with those of amoxicillin given as a 1-g oral dose three times daily for treatment of community-acquired pneumonia suspected to be due to Streptococcus pneumoniae. Success of treatment was determined by a combination of clinical assessment and chest radiography. Pneumococcal pneumonia was the confirmed diagnosis for 177 patients (54%). Overall rates of success among evaluable patients were equivalent between drugs, both at the end of treatment (sparfloxacin, 92%; amoxicillin, 87%) and at follow-up (sparfloxacin, 89%; amoxicillin, 84%). Sparfloxacin was well-tolerated and produced fewer gastrointestinal effects than amoxicillin. In conclusion, sparfloxacin is a safe and effective alternative to high-dose amoxicillin for the treatment of suspected pneumococcal community-acquired pneumonia.