Antiepileptic drugs may cause the changes in the oxidant/antioxidant status of the body. Reactive oxygen species have been suggested to be an important factor in the pathogenesis of various diseases as well as drug interactions and/or adverse effects. The aim of this study, therefore, is to investigate the status of major antioxidant enzyme activities as well as the end products of lipid peroxidation in erythrocyte and plasma from epileptic children after therapy with sodium valproate (VPA). Superoxide dismutase (SOD), catalase (CAT) activities and malondialdehyde (MDA) levels in erythrocyte and plasma were analyzed in 41 epileptic patients under long-term antiepileptic therapy with VPA and 32 healthy controls. Erythrocyte SOD activity was found to be increased (p=0.024) whereas erythrocyte CAT activity decreased (p=0.016) in patients with epilepsy under VPA treatment compared to the controls. MDA levels in erythrocyte were found to be markedly decreased in epileptic children compared to controls (p<0.001). In conclusion, decreased CAT activity seems to be compensated with increased SOD activity in erythrocytes protecting erythrocyte membranes from lipid peroxidation in patients with epilepsy under VPA treatment.