Abstract： Objective To determine whether the polymorphism A1166C in the angiotensin Ⅱ type 1 receptor (AT1R) gene is associated with essential hypertension Methods A casecontrol study was carried out using 125 hypertensive and 103 normotensive subjects The AC variant at position 1166 (A1166C) of the AT 1R gene was identified by polymerase chain reaction (PCR) and PCR/restriction fragment length polymorphism (PCR/RFLP) analysis The digestion products were separated on 2% agarose gels and visualized with ethidium bromide under ultraviolet ray Results The differences in C1166 allele frequency and in the AC genotype distribution of the AT 1R gene between the hypertensive and normotensive groups were statistically significant (C allele: 0.092 vs 0.034, χ2=6.1.86,P<0.05; AC genotype: 0.184 vs 0.068, χ2=6.654,P<0.05) Conclusion The AC genotype is associated with essential hypertension, and the C allele may be a marker for predisposition to hypertension in Chinese Han population