OBJECTIVE: To prospectively clarify the relationship between angiotensin converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and diabetic nephropathy (DN) in Type 2 diabetic patients. METHODS: We examined 66 Type 2 diabetic patients with normal buminure. All patients suffered from diabetes mellitus for more than 5 years and matched well in age, body mass index (BMI), mean arterial pressure (MAP), fasting blood sugar (FBS), and urinary excretion of albumin (UAE). Patients were classified into 3 groups according to genotypes of ACE. ACE gene I/D polymorphism was identified by polymerase chain reaction (PCR). The patients were followed up for 5 years and their UAE, serum creatinine (Scr), and HbAlc were checked once a year. RESULTS: Eight subjects (12%) were discontinued prematurely. At the end of the study, there were no significant differences in the clinical parameters such as BMI, MAP, FBS, HbA1c, UAE, and Scr among the 3 groups (P > 0.05), and also in DN incidence in Type 2 diabetic patients among the 3 groups (II 45.8%, ID 52.3%, and DD 46.1%, respectively, P > 0.05 ). The increased degree of UAE among the 3 groups was similar at the end-point of the study (P > 0.05). CONCLUSION: The DD genotype of ACE gene may not be a clinically useful genetic marker for predicting the genesis and development of DN in Type 2 diabetic patients in Chinese. There is no association between ACE gene I/D polymorphism and the genesis and development of DN in Type 2 diabetic patients.