This paper deals with malformations detected in 26 of 315 newborns of 305 epileptic mothers followed prospectively. In 3 more cases, malformations were detected in utero and therapeutic abortion was performed. Two hundred and seven women were on monotherapy, 102 on polytherapy and 9 were not treated. In total, malformations overall incidence was 9.1%. Minor anomalies were detected in 42 newborns (13.3%). A higher rate of malformations and minor anomalies was found among offspring of mothers treated with valproic acid (VPA). In the VPA group, mothers of malformed babies had higher plasma levels in the first trimester than mothers of babies without malformations. The need for accurate prenatal diagnostic studies in pregnant women with epilepsy is stressed.