Abstract: Objective To investigate synergistic interaction between the C825T polym orphism of G protein β₃ subunit gene(CNB3) and the M235T polymorphism of angiotensinogen gene (ACT) in essential hypertension(EH).Methods Polymerase chain reaction combined with restriction enzym a digestion was used to detect the C825T polymorphism of CNB3 gene and M235T polymorphism of ACT gene in 162 hypertensive patients and 180 nounotensive controls.Results There was no significant difference of the CNB 3 gene C825T polymorphism CC,CT,TT genotypes and T alleles between hypertensive patients and noun otensive controls.The frequencies of CT+TT genotypes and T allele of ACT gene M235T polymorphism in EH were significantly higher than that of in control group.The odds ratio of EH for subjects with CNB3 TT genotype and ACT TT genotype(3.45) wasmarkedly increased compared to the subjects with ACT TT genotype(1.87) alone.Conclusion ACT 235T should be a risk factor for EH in Shandong Han population and there was a significant syner gistic effect of CNB3 235T allele and ACT 235T allele in EH.