In a follow-up study long-term effects of antenatal exposure to two anticonvulsant drugs, phenobarbital and carbamazepine on central nervous system development were evaluated. Children aged 6 to 13 years of epileptic mothers who used phenobarbital (n = 13), carbamazepine (n = 12), phenobarbital plus carbamazepine (n = 12), or no medication (n = 24) during pregnancy were studied. None of the mothers had seizures during pregnancy. A control group carefully matched for confounding variables was selected of children of nonepileptic mothers (n = 61). Minor and major congenital anomalies appeared to be more related to mother's epilepsy than to maternal medication. There were no neurologic differences between the groups. Exposure to phenobarbital was associated with smaller head circumference. An accompanying negative effect of phenobarbital on cognitive development was suggested. Further research on this intriguing phenomenon seems warranted.