To clarify the relationship among angiotensin 1-converting enzyme(ACE) gene insertion/deletion(I/D) polymorphism, serum ACE activity, and diabetic retinopathy in Type II diabetic patients, we examined 36 healthy controls, 40 Type II diabetic patients without diabetic retinopathy, and 68 Type II diabetic patients with diabetic retinopathy. All of patients suffered from Type II diabetes beyond 5 years and matched in age and body mass index. An insertion/deletion polymorphism of ACE gene was identified by polymerase chain reaction(PCR). Serum ACE activity was determined using spectrophotometry. The distribution of DD, ID, and II genotypes of the ACE gene did not differ among the three groups (16.7%, 33.3%, and 50.0% in the healthy controls; 22.5%, 35.0%, and 42.5% in Type II diabetic patients patients without diabetic retinopathy; and 20.6%, 30.9%, and 48.5% in Type II diabetic patients with diabetic retinopathy; respectively). The frequency of ACE I/D genotypes was not significantly different between non-proliferative retinopathy and proliferative retinopathy of Type II diabetic patients with diabetic retinopathy (P > 0.05). Serum ACE activity of three groups was similar (P > 0.05). These results do not support the hypothesis that the DD genotype of the ACE gene would be a clinically useful genetic marker for predicting the development of diabetic retinopathy in Type II diabetic patients. There is no association between ACE gene I/D polymorphism and the prognosis of diabetic retinopathy in Type II diabetic patients. ACE may not involve in forming diabetic retinopathy in Type II diabetic patients.