To examine whether interleukin1β gene (511) polymorphism is associated with therapeutic effect of a kind of angiotensin 1 converting enzyme inhibitors (ACEIs), benazepril. Individuals with essential hypertension were recruited from Yuexi County (n=594) and Huoqiu County (n=352), in Anhui, China, and were treated with benazepril for 15 consecutive days. Patients' blood pressure was measured and blood sample from subjects were collected. The interleukin1β (511) genotype was determined using the polymerase chain reactionrestriction fragment length polymorphism (PCRRFLP) analysis. Linear and logistic regressive analyses were conducted to test for the association between interleukin1βgenotype and drug response. In linear regression the blood pressure drop was considered as the dependent variable. In logistic regression the drug response was considered as a dichotomized trait. Covariates were adjusted in the regression models. Both Linear and logistic regression analyses showed that there is no association between interleukin1β (511) polymorphism and blood pressure drop after 15 days of benazepril treatment in samples from both Huoqiu and Yuexi. Combination of data from both places yielded similar results, this suggests that interleukin1β genotype probably does not affect the therapeutic effect of benazepril.