In this multicentre, multinational, comparative, double-blind clinical trial, outpatients with both clinical signs and symptoms and radiographic evidence of acute sinusitis were randomly assigned to receive for 7 days either a twice-daily oral regimen of faropenem daloxate (300 mg) or a twice daily oral regimen of cefuroxime axetil (250 mg). Among 452 patients considered valid for clinical efficacy, faropenem daloxate treatment was found to be statistically equivalent to cefuroxime axetil (89.0% vs. 88.4%-95% CI=-5.2%; +6.4%) at the 7-16 days post-therapy assessment. At 28-35 days post-therapy, the continued clinical cure rate in the faropenem daloxate group was 92.6% and that for the cefuroxime axetil group was 94.9% (95% CI: -6.8%; +1.2%). A total of 148 organisms was obtained in 136 microbiologically valid patients (30.1%). The predominant causative organisms were Streptococcus pneumoniae (47.1%), Haemophilus influenzae (30.1%), Staphylococcus aureus (14.7%) and Moraxella catarrhalis (8.8%). The bacteriological success rate at the 7-16 days post-therapy evaluation was similar in both treatment groups: 91.5% and 90.8% in the faropenem daloxate and cefuroxime axetil groups, respectively (95% CI=-9.2%; +9.5%). Eradication or presumed eradication was detected for 97.3% and 96.3% of S. pneumoniae, 85.0% and 90.5% of H. influenzae, 88.9% and 90.9% of S. aureus and 100.0% and 83.3% of M. catarrhalis in faropenem daloxate and cefuroxime axetil recipients, respectively. At least one drug-related event was reported by 9.5% of the faropenem daloxate-treated patients and by 10.3% of those who received cefuroxime axetil. The most frequently reported drug-related events were diarrhoea (2.2% versus 2.9%), nausea/vomiting (1.5% vs. 0.7%), abdominal pain (0.7% vs 1.5%) and skin reactions (1.5% vs. 1.1%). Overall, faropenem daloxate was at least as effective clinically and bacteriologically as cefuroxime axetil and was well tolerated.