Five children, aged 3 to 11 years, treated with carbamazepine for epilepsy, had an acute aberrant reaction characterized by the onset of myoclonic, atypical absence and/or atonic (minor motor) seizures within a few days. When the carbamazepine was discontinued, two of the children returned to their former state very quickly, two had the minor motor seizures resolve in 3 and 6 months, and one had the seizures persist. The child in whom the seizures persisted was later found to have ceroid lipofuscinosis. The other children are doing well on other anticonvulsants.