Objective: Studies show that anti-epileptic drugs increase oxidative stress. Thus, low-density lipoprotein oxidation increases and atherogenesis is induced. Paraoxonase-associated high-density lipoprotein protects low-density lipoprotein and high-density lipoprotein oxidation The effects of anti-epileptic drugs on paraoxonase activity has not been investigated yet. The aim of this study is to investigate the effect of antiepileptic drugs on paraoxonase activity, lipid profiles, flat, vitamin B-12, homocysteine, thyroid hormones, apolipoprotein A-1, total anti-oxidant capacity, malondialdehyd, nitric oxide, and oxidised low-density lipoprotein The association with carotid femoral pulse wave velocity and current biochemical parameters had been searched for assessing the effects of anti-epileptic drugs on the vascular system Patients and methods: We recruited 59 epileptic patients treated with anti-epileptic drugs and 23 controls (group IV) at least 6 months ago. The epileptic group was divided into three groups by receiving anti-epileptic drugs as follows, group carbamazepine, group II valproic acid, and group III carbamazepine and valproic acid. Arterial distensibility was assessed with the Complior device. Results. There was no difference between the current biochemical parameters in epileptic children Serum-free T4 was decreased, when compared with group IV. Thyroid-stimulating hormone was increased in group II, compared with group IV The carotid-femoral pulse wave velocity was increased in group Ill, compared with group IV The carotid femoral pulse wave velocity was correlated with thyroid-stimulating hormone and valproic acid levels Conclusions: Anti-epileptic drugs may induce atherogenesis by affecting the thyroid hormones. According to the current data, the effects of thyroid hormones on vascular system may be independent of other biochemical markers Epileptic patients using antiepileptic drugs must be followed closely for arterial stiffness, and also for the development and progression of atherosclerosis.