This randomized, multicentre, double-blind, double-dummy study assessed the efficacy and safety of 7 or 10 day regimens of grepafloxacin, 600 mg od, compared with amoxycillin, 500 mg tds, in the treatment of community-acquired pneumonia (CAP). A total of 264 patients were recruited at 43 centres (127 received grepafloxacin and 137 received amoxycillin), of whom 207 patients (78%) completed the study. Clinical and microbiological efficacy were assessed at the end-of-treatment visit (3-5 days after the last dose) and at the follow-up visit (28-42 days after the last dose). At follow-up, patients in the evaluable population treated with grepafloxacin demonstrated a clinical response rate (76%; 87/114) equivalent to that seen with amoxycillin (74%, 85/111, 95% CI = -12%, 10%) while, in the intent-to-treat population with a documented bacterial pathogen, the clinical success rate in the grepafloxacin group (78%, 29/37) was significantly higher than in the amoxycillin group (58%, 28/48), 95% CI = 2%, 43%). In patients from the evaluable population in whom the pathogens were documented the clinical success rate favoured grepafloxacin, compared with amoxycillin (79%, 26/33 versus 63%, 26/42, respectively; 95% CI = -5.2%, 38.1%). Microbiological eradication with grepafloxacin was statistically superior to amoxycillin in the evaluable population; the success rate was 89% (32/36) in the grepafloxacin group compared with 71% (32/45) for the amoxycillin group (95% CI = 2%, 37%). The pathogens most commonly isolated from patients were Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae. The success rates for infections caused by S. pneumoniae and H. influenzae at follow-up were higher with grepafloxacin than with amoxycillin. Grepafloxacin was well tolerated, with a safety profile comparable to that of amoxycillin. The therapeutic judgement of patients and investigators at the patient's last visit, as well as the assessment of individual respiratory signs and symptoms, yielded comparable results with both treatments. The results of this study indicate that grepafloxacin, 600 mg od for 7-10 days, is equivalent to or better than amoxycillin, 500 mg tds for 7-10 days in achieving a successful clinical and microbiological response in the treatment of patients with CAP.