This double-masked, multicenter, randomized clinical trial compared the efficacy and tolerability of cefuroxime axetil and amoxicillin/clavulanate in the treatment of acute bacterial maxillary sinusitis. A total of 263 patients with acute bacterial maxillary sinusitis were randomly assigned to receive 10 days of treatment with either cefuroxime axetil 250 mg twice daily (n = 132) or amoxicillin/clavulanate 500/125 mg 3 times daily (n = 131). Patients' responses to treatment were assessed once during treatment (6 to 8 days after the start of treatment), at the end of treatment (1 to 3 days posttreatment), and at follow-up (26 to 30 days after cessation of treatment). Clinical success, defined as cure or improvement, was equivalent in the cefuroxime axetil and amoxicillin/ clavulanate groups at the end-of-treatment and follow-up assessments. Patients in both groups showed improvements in symptoms of acute sinusitis at the during-treatment visit. Treatment with amoxicillin/clavulanate was associated with a significantly higher incidence of drug-related adverse events than treatment with cefuroxime axetil (29% vs 17%), primarily reflecting a higher incidence of gastrointestinal adverse events (23% vs 11%), particularly diarrhea. Two patients in the cefuroxime axetil group and 8 patients in the amoxicillin/clavulanate group withdrew from the study due to adverse events (P = 0.06). These results indicate that cefuroxime axetil 250 mg twice daily is as effective as amoxicillin/clavulanate 500 mg 3 times daily in the treatment of acute sinusitis and produces fewer gastrointestinal adverse events. cefuroxime axetil, amoxicillin/clavulanate, acute sinusitis.