Objective Using mutagenically separated allele-specific polymerase-chain-reaction (MS-PCR) technique to determine the correlation between angiotensinogen gene M235T (Ag TM235T) polymorphism and the onset of familial essential hypertension in the population from Jiangsu and Anhui Provinces. Methods (1) Establish and compare the optimal reaction system of PCR-RFLP and MS-PCR technique to detect AgTM235T polymorphism. (2) All subjects were divided into four groups: 62 patients with both hypertension and familial background (FH), 32 normal persons who had familial background (FNH), 26 persons in control group (N) and 10 patients with hypertension but without familial background (NFH group). The genotype of all subjects was determined by MS-PCR technique.Results (1) The frequency of T allele in PCR-RFLP was 0.5, much lower than 0.95 in MS-PCR, which was demonstrated by DNA sequencing. (2) The TT-genotype and the frequency of T allele (TT/T) in FH and FNH groups were much higher than those in N and NFH groups (0.581/0.766 and 0.563/0.766 vs 0.346/0.577 and 0.40/0.550, P<0.005). (3) Persons developing hypertension in FNH group were much younger than other three groups (28.07±9.72 , P<0.025). Conclusion (1) Compared with PCR-RFLP, MS-PCR is a rapid, simple and reliable technique for detection gene polymorphism of Ag TM25T. (2) In Jiangsu and Anhui area, the present study confirms the observation of a higher frequency of the 235T allele of the angiotensinogen gene in hypertension and identifies individuals with family history. Concerning of the age, we might speculate that the AgTM235T polymorphism is only associated with familial essential hypertension.