Objective To investigate the correlation between the alleles polymorphism of CYP2A6 and CYP2B6 and blood concentration of Valproate sodium(VPA).Methods The 165 epilepsy patients received simplex VPA and without dysfunction of liver and kidney were chose in this study.The alleles polymorphism of CYP2A6 in 95 cases and CYP2B6 in 70 cases were detected by polymerase chain reaction(PCR).Fluorescence polarization immunoassay(FPIA) was used to measure the blood concentration of VPA.Results The frequence of allele CYP2A6*4 in 95 cases was 13.2%.The blood concentration of VPA in patients with allele CYP2A6*4[(4.23?0.27)mg/ml]was significantly higher than that in patients without allele CYP2A6*4[(3.35?0.38)mg/ml](P