Angiotensin converting enzyme (ACE) genotypes have been associated with hypertension in the general population. However, the relation of ACE genotype to the prevalence of hypertension in diabetic populations is less clear. This study investigated ACE genotypes in 100 patients with diabetes mellitus, of whom 41 were on anti-hypertensive medication. A significant association was found between the presence of the ACE-D allele and hypertension in both the overall diabetic group (D = 0.66, P < 0.01) and in the subset of diabetics who had non-insulin-dependent diabetes (D = 0.69, P < 0.001). There was no correlation of ACE genotype with hypertension in insulin-dependent diabetes (D = 0.57).