Objective To investigate the association of angiotensin converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism with type 2 diabetes mellitus (T2DM). Methods Two hundred and nine patients with T2DM diagnosed based on the criteria for diabetes mellitus in 1999 by WHO and 221 controls were recruited from general population of Dongcheng District in Beijing. All subjects were genotyped for the I/D polymorphism of ACE gene by PCR-fragment length polymorphism (FLP) assay. Blood pressure, levels of plasma glucose, lipids and serum insulin were determined. Body mass index (BMI), waist-hip ratio (WHR) and homeostasis model assessment-insulin resistance index (HOMA-IR) were calculated. Results The genotype frequencies for ACE genes DD, ID, and II were 19.1%, 42.1%, and 38.8% in patients, respectively, and 9.6%, 49.4%, and 41.0% in controls, respectively. The ACE DD genotype frequency was significantly higher in patients than in controls (χ2=7.61, P=0.022). Multivariate logistic regression analysis showed that the ACE DD genotype was a risk factor for T2DM, with the OR of 2.35 (95% CI 1.17-4.71) adjusted for age, sex, BMI, WHR, blood pressure, and serum cholesterol levels. Conclusion The ACE DD genotype is associated with the increased susceptibility to type 2 diabetes mellitus. Objective To investigate the association of angiotensin converting enzyme (ACE) gene insertion / deletion (I / D) polymorphism with type 2 diabetes mellitus (T2DM). Methods Two hundred and nine patients with T2DM diagnosed based on the criteria for diabetes mellitus in 1999 by WHO and 221 controls were recruited from general population of Dongcheng District in Beijing. All subjects were genotyped for the I / D polymorphism of ACE gene by PCR-fragment length polymorphism (FLP) assay. Blood pressure, levels of plasma glucose, lipids and serum Results The genotype frequencies for ACE genes DD, ID, and II were 19.1%. The genotype frequencies (BMI), waist-hip ratio (WHR) and homeostasis model assessment- insulin resistance index (HOMA- Respectively, and 9.6%, 49.4%, and 41.0% in controls, respectively. The ACE DD genotype frequency was significantly higher in patients than in controls (χ2 = 7.61, P = 0.022). Multivariate logistic regre ssion analysis showed that ACE DD genotype was a risk factor for T2DM, with the OR of 2.35 (95% CI 1.17-4.71) adjusted for age, sex, BMI, WHR, blood pressure, and serum cholesterol levels. Conclusion The ACE DD genotype is associated with the increased susceptibility to type 2 diabetes mellitus.