Very little data are available on the usefulness of oxcarbazepine in young children with epilepsy. From January 1991 through October 1994, we treated 53 children under age 7 years with oxcarbazepine. The mean follow-up with oxcarbazepine treatment was 13 months. Etiology was symptomatic in 39, cryptogenic in 12, and idiopathic in 2 children. Forty-three children had previously been intractable to one or more antiepileptic drugs (including carbamazepine in 30 patients) and two had carbamazepine hypersensitivity. The age at onset of oxcarbazepine therapy ranged from 0.6 to 6.9 years (mean, 3.9 yr). The mean maximum oxcarbazepine dose was 50 mg/kg/day (range, 21-86 mg/kg/day). Of the children with localization-related epilepsy, 12 of 44 (27%) became seizure free and an additional 16 of 44 (36%) had an at least 50% reduction of seizures. Five of nine children with generalized epilepsy also had some benefit but none became seizure free. In the 33 children with at least 50% seizure reduction, the mean effective dose and trough serum level of the active metabolite monohydroxycarbazepine were 47 mg/kg/day (range, 21-75 mg/kg/day) and 91 micromol/L (range, 42-130 micromol/L), respectively. Efficacy was transient in 4 children; side effects were observed in 17 children (32%); in 9 (17%) of whom, they led to dose reduction or discontinuation. Oxcarbazepine appears to be an effective and well-tolerated drug for localization-related early childhood epilepsy. Young children need a higher dose per body weight than adults.