The relationship between diabetic complications and age, sex, duration, mode of therapy, body weight, control of blood glucose, blood pressure, and serum triglyceride and cholesterol was analyzed in a population with non-insulin-dependent diabetes in Japan. The prevalences of complications in the subjects varied from 6.5% for cerebrovascular strokes to 85.1% for sclerotic changes in retinal vessels; 35.8% of the patients had diabetic retinopathy and 19.8% had proteinuria. Univariate and multivariate analyses revealed that control of diabetes (blood glucose, mode of therapy, and duration) was closely correlated with retinopathy and proteinuria. However, blood glucose did not correlate with coronary insufficiency or cerebrovascular strokes. These macrovascular complications were related to aging and blood pressure. The data suggested that not only good glycemic control but also sufficient antihypertensive therapy was necessary for treating diabetic patients. The coefficient of determination of the risk factors was calculated for each diabetic complication. Except for sclerotic changes in retinal vessels, the coefficients were too small to fully explain the development of diabetic complications, especially for macrovascular diseases. The current data suggest that susceptibility of the individual patients to the diabetic complications is an important determinant.