In a study of infants of parents with epilepsy, malformations were twice as prevalent in these children as in controls. Children of mothers with epilepsy had more minor anomalies than those of fathers with epilepsy or controls. At 1 year of age, a greater number of minor anomalies was seen in children of mothers with epilepsy who had received treatment with antiepileptic drugs (AEDs) during pregnancy, whereas at 4 years, no difference was observed. Type of epilepsy, seizures during pregnancy, plasma levels of phenytoin or phenobarbital in the medium range, and fetal intrauterine growth did not correlate with the number of minor anomalies. We suggest that the special genetic background that predisposes to epilepsy also renders the fetus more vulnerable to major and minor anomalies. Although linkage between epilepsy and malformation is stronger than between AEDs and malformations, valproate, phenytoin, and phenobarbital show specific teratogenic effects. In addition, all AEDs unspecifically increase the number of minor anomalies. Under therapeutic conditions, valproate may be regarded as considerably teratogenic and all other observed AEDs as weakly teratogenic.