Autopsy cases from Annual Report of Autopsy Cases published by the Japan Society of Pathology showed an increase of myocardial infarction from 13.2% in the years 1958-65 to 26.6% in the years 1983-85. However, cerebral infarction and hemorrhage showed no definite increase during the period. Frequency of diabetes mellitus was extremely increased among the cases of myocardial infarction who were admitted to our hospital. Arteriographic characteristics of coronary atherosclerosis in diabetics consist of multiple tight stenoses in one major artery and two or three arterial obstructions. Carotid arterial blood flow and plaque formation and calcification of the arteries were examined by doppler imaging technology and B-mode (5 MHz) real time ultrasound using ultrasonographic equipment in diabetic patients. Both blood flow volume and blood flow velocity in the elderly patients with diabetes mellitus (over 65 years old) were significantly reduced compared with those in the younger patients with diabetes mellitus (7.4 +/- 0.4 vs. 8.5 +/- 0.2 in blood flow volumes. p < 0.01; 12.4 +/- 0.8 in blood flow velocities. p < 0.01). Plaque formation and calcification of carotid arteries were significantly more frequent in the elderly patients with diabetes mellitus than in the younger patients with diabetes mellitus (p < 0.05). Asymptomatic cerebral infarction was studied in 37 diabetic patients by brain magnetic resonance imaging (MRI) in the absence of prior stroke. T2 weighted MRI imaging showed 27 patients among 37 patients (73%) to suffer from lacunar infarction. Hyperintensities were seen in the brain stem (28.6%), white matter (62.9%), basal ganglia (60.0%), and paraventricular areas (PVH) (20.0%).(ABSTRACT TRUNCATED AT 250 WORDS)