BACKGROUND The long half-life of azithromycin allows for single-dose oral therapy for acute otitis media (AOM). OBJECTIVE This study was designed to compare the efficacy and tolerability of single-dose azithromycin with 10-day, twice-daily amoxicillin/clavulanate for the treatment of new-onset, uncomplicated AOM in children. METHODS Children aged 6 months to 12 years with new-onset AOM were randomly assigned to receive either a single 30-mg/kg dose of azithromycin or standard-dose amoxicillin/clavulanate (45 mg/kg administered BID for 10 days) in a double-blind, double-placebo, multicenter clinical trial. The diagnosis of AOM was based on specific clinical signs and symptoms, and was confirmed by pneumatic otoscopy and acoustic reflectometry (level ≥3). Clinical response was assessed on days 12-16 and 28-32. RESULTS Mean (SD) age of children receiving azithromycin (n = 173) or amoxicillin/clavulanate (n = 173) was 2.7 (2.3) years and 3.4 (2.8) years, respectively, with 43% and 36% ≤2 years of age. Most (53.2%) of the children were boys, and most (51.2%) were white. Clinical success rates (intent-to-treat) for azithromycin and amoxicillin/clavulanate, respectively, were 87% and 88% (95% CI, -9.2 to 6.5) on day 12-16 and 75% and 75% (95% CI, -10.2 to 10.5) on day 28-32. The incidences of treatment-related adverse events for azithromycin and amoxicillin/clavulanate were 16.8% and 22.5%, respectively. Corresponding rates of diarrhea were 6.4% and 12.7%, respectively. Vomiting, which was generally mild, occurred in 7 children in each group. One azithromycin patient and 5 amoxicillin/clavulanate patients discontinued treatment because of adverse events. The compliance rate for azithromycin was significantly higher than that for amoxicillin/clavulanate (99% vs 83%; P<0.001). CONCLUSIONS In this trial comparing the efficacy of single-dose azithromycin (30 mg/kg) with twice-daily amoxicillin/clavulanate (45 mg/kg) for the treatment of new-onset, uncomplicated AOM, no differences were detected between the 2 regimens. Single-dose azithromycin was generally well tolerated and provides an alternative to conventional oral regimens for AOM.