Type 2 diabetes is one of the most challenging health problems throughout the world and is increasing at an alarming rate. Most clinical evidence involved in therapeutic guidelines for diabetes is derived from European or American cohort studies, and the characteristics of diabetes in Asians, including Japanese, have been only poorly investigated to date, despite Asians constituting approximately half of the world diabetes population. The Japan Diabetes Complications Study (JDCS) is a nationwide multi-center prospective study of type 2 diabetic patients. In 1996, 2, 205 patients aged 40-70 years with previously diagnosed type 2 diabetes were recruited from 59 Japanese institutes that specialize in diabetes care. Parameters related to their diet, exercise, glycemic control, diabetic complication events, dyslipidemia, hypertension, obesity and quality of life have been measured and collected every year until now. It was clarified from the interim results of JDCS that the characteristics and pathophysiological backgrounds of diabetes in East Asians were quite different from those in Caucasian subjects. Compared with Caucasian diabetic patients, the JDCS patients had a much lower body mass index (BMI). Moreover, whereas the mean BMI of Caucasian diabetic patients was higher than that reported for non-diabetics of the same ethnic origin, the mean BMI of Japanese diabetic patients was normal in comparison with the Japanese non-diabetic population. Other differences between Japanese and Caucasian patients with type 2 diabetes could be found in the incidence rate and risk factors of complications, the effects of moderate alcohol drinking on cardiovascular disease, and the clinical significance of the diagnosis of metabolic syndrome. These profound differences demonstrate the necessity for obtaining clinical evidence based on a large-scale study of East Asian patients in order to establish and provide management and care specific to this particular population.