We studied plasma GSTA1-1 concentrations in preconceptionally recruited epileptic women who received antiepileptic drugs (n = 99) and a control group of healthy women (n = 106). Mean plasma GSTA1-1 concentrations in the control group did not show significant changes preconceptionally and throughout pregnancy. Six weeks postpartum, however, a significant increase in the mean plasma GSTA1-1 concentration (p < 0.001) was found as compared to preconceptional levels and levels during pregnancy. The mean plasma GSTA1-1 concentration in epileptic women was significantly higher in the 4th gestational week compared to those determined in healthy pregnant women (1.68 versus 1.08 microg/l, p < 0.001). Values between the groups in the second and third trimester and postpartum period showed no significant differences.