Data have been presented on the finding of glycosuria and the diagnosis of diabetes mellitus during four years of a long-term study of the health of population samples of Hiroshima and Nagasaki. Diabetes and glycosuria are much more common in Hiroshima than in Nagasaki and in both cities these findings are more frequent in males than in females. The prevalence of diabetes appears to be increasing in Hiroshima males. Findings in diabetics were compared with nondiabetics. In general, Japanese diabetics are similar to diabetics in other countries concerning their increased risk of obesity, hypertension, proteinuria, hypercholesterolemia, and cardiovascular and cerebrovascular diagnoses. This is of particular interest in the light of evidence that ketosis and severe abnormalities of carbohydrate metabolism are rare in Japan as compared to Western countries. Despite a lower prevalance of diabetes in Japanese females than in males, the abnormalities associated with diabetes appear to occur more commonly in female diabetics than in male diabetics.