Objective. To compare the clinical efficacy of a 5-day cefdinir course with a 10-day cefprozil course in the treatment of pediatric acute otitis media (AOM). Design. Comparative, investigator-blinded multicenter trial. Setting: Primary care, ambulatory, Patients. Children ages 6 months through 12 years with clinical symptoms and tympanic membrane signs of AOM, plus tympanometric-confirmed middle ear effusion in at least 1 ear. Of the 435 patients enrolled in the study, 373 were evaluable, Intervention. Patients received cefdinir 14 mg/kg/day divided twice a day for 5 days or cefprozil 30 mg/kg/day divided twice a day for 10 days. Main outcome measures. Clinical resolution of tympanic membrane signs and symptoms of AOM determined at end of therapy on Study Days 9 to 11, Results. The clinical cure rate at end of therapy was 80% (152 of 190) for cefdinir-treated patients and 82.5% (151 of 183) for cefprozil-treated patients (95% confidence interval, 10.43% to 5.4%), Diarrhea and overall adverse reactions, respectively, occurred in 7.8 and 13% of cefdinir-treated patients and in 4.2 and 12% of cefprozil-treated patients. Conclusions, A short course 5-day regimen of cefdinir was as clinically effective and well-tolerated as a 10-day regimen of cefprozil in the treatment of nonrefractory AOM.