The prevalence of peripheral vascular disease (PVD) was determined in 296 Japanese diabetics (mean age 55.2 years, range 19 to 79 years), using a Doppler ultrasonic technique. PVD was diagnosed in 11.5% of the diabetic patients (7.6% females, 14.6% males). In 88% of all patients with PVD, asymptomatic impaired circulation was diagnosed. There was a clear increase of PVD with age. It was found that the increase of PVD was gradual in patients under the age of 70, from 4.3% in the younger group to 10% in patients in their 7th decade, while the frequency of PVD rose sharply to 25% in patients in their 8th decade and over. The occurrence of PVD was significantly correlated with hypertension, hypertriglyceridemia and past obesity, but not with glycemic control, serum cholesterol levels or smoking habits. Also, PVD was closely associated with persistent proteinuria, retinopathy at a rather advanced stage and calcification of leg arteries. These findings suggest that the frequency of PVD in Japanese diabetics is lower by one third and progression of PVD is more gradual than that found in similar studies in Western countries. Another distinctive feature of PVD in Japanese diabetics was the markedly high percentage of asymptomatic cases.