Objective To investigate the relationship between the mutagenicity of carbamazepine (CBZ) and folic acid (FA), and to explore the mechanism of CBZ teratogensis and the prevention effect of the folic acid. Methods Peripheral blood lymphocyte chromosome aberration rate (CAR), sister chromatid exchange (SCE)frequencies, and serum FA levels have been studied in 15 CBZ -treated epileptic patients, 15 CBZ plus FA-treated epileptic patients The untreated epileptic patients and the health subjects were served as controls Results CAR and SCE frequencies were significantly higher in CBZ group as compared with the CBZ plus FA group and the controls ( P