The aim of this study was to assess the influence of pregnancy on trimestral frequency of epileptic seizures. The seizure frequency was studied retrospectively in 50 pregnant epileptic women compared to one year before the onset of pregnancy, for each trimester of pregnancy separately, and for the whole duration of pregnancy. In the first trimester 18% of the pregnant epileptic women had an increased seizure frequency. There was no change in seizure frequency in 56% of pregnancies. In 26% of the pregnant women the number of seizures was decreased. In the second trimester, pregnancy did not influence seizure frequency in 60% of the pregnancies; 16% of the women had increased frequency of seizures and 24% had decreased frequency. In the third trimester, 20% of the pregnant epileptic women had higher seizure frequency. In 56% of the women no change in seizure frequency was recorded during pregnancy. For the entire period of pregnancy, 22% of the pregnant epileptic women had an increased seizure frequency, 54% had no change, and 24% had lower frequency as compared to one year before conception. No difference of seizure frequency was noted between trimesters and the whole course of pregnancy.