Non-fatal or small infarction, especially with multiple occurrence, is a feature of cerebrovascular disease complicating diabetes mellitus. The atherosclerosis of the cervical and cerebral arteries, especially in the posterior circulation, in diabetes is more severe than that in non-diabetics. We reviewed the incidence of vascular lesions, and clinical history in 25 male and 26 female diabetic autopsy subjects. In addition, the long-term effects of blood pressure and glucose values were evaluated in 267 stroke patients without cerebral embolism, 99 of whom had diabetes mellitus. Asymptomatic cerebral infarction is not rare in diabetic subjects, and can now be accurately pathologically and clinically evaluated using MRI. The results of our study indicate that high blood pressure and poor blood glucose control are associated with the higher incidence of cerebral infarction in the diabetic patients.