Before the 1980s, only limited community-based data were available on the prevalence of diabetes in Japan. The prevalence of diabetes in subjects older than 40 years was 2-5%. In many surveys carried out in the 1990s, all subjects were examined using the 75 g glucose tolerance test and diabetes was diagnosed according to the WHO criteria. Diabetes was found in about 10% of the population older than 40 years. A higher prevalence in Japanese immigrants in the United States suggests that change of environmental factors, such as increased intake of animal fat, might further increase the prevalence of diabetes in Japan in the future. The mean BMI of NIDDM patients at their initial visit to our hospital is 22.9 + 3.4 kg m-2, compared to patients in many other developed countries and diabetic Japanese Americans. Regarding causes of death in Japanese diabetic patients, the most frequent causes were vascular diseases including renal failure 11.2%, ischaemic heart diseases 14.6%, and cerebrovascular diseases 13.5%, thus atherosclerotic diseases were less frequent compared to the data in the United States. Each year, approximately 6000 diabetic patients start haemodialysis, and diabetic retinopathy is the main cause of acquired blindness in Japan.