OBJECTIVE To investigate whether angiotensinogen(AGT) M235T, angiotensin II type I receptor(AT(1)R) gene A1166C and angiotensin converting enzyme(ACE) gene I/D polymorphism are implicated in human essential hypertension(HT) in Chinese. METHODS Polymerase chain reaction(PCR) and PCR combined with restriction enzyme digestion were used to detect AGT gene M235T, AT(1)R gene A1166C variations and ACE gene I/D polymorphism in 161 hypertensive patients and 134 normotensive controls. RESULTS No statistically significant differences were found in frequencies of the ACE D allele, AGT gene 235T and AT(1)R A1166C between hypertensive patients and normotensive controls, but in hypertensive patients aged <60 years the frequencies of the ACE D allele and AGT gene 235T were significantly higher than those of the normotensive controls (P<0.05). The analysis of combined genotypes of AGT gene and ACE gene showed that the combined genotypes of DD-TT and ID-TT were significantly higher in hypertensive patients than in normotensive controls. Significant relationships between the ACE genotype and serum ACE activity were found in both groups(P<0.05). CONCLUSIONS The ACE D allele and AGT 235T polymorphism may be involved in the early occurrence of HT. The combined genotypes of DD-TT and ID-TT may be a dangerous genetic factor for HT in Chinese.