Vascular murmurs were routinely sought over the carotid arteries in 1,777 outpatients of 40 years of age or older who attended the cardiovascular clinic of our institute, and carotid bruits were heard in 82 patients (4.6%). The prevalence of carotid bruits increased with age from 5/467 (1.1%) in patients aged 40 to 49 years to 26/150 (17.3%) in those aged 70 to 79 years. Calcification of the carotid arteries was examined by posteroanterior films of the cervical spine in 447 patients 60 years of age or older and carotid calcification was found in 20 (42.6%) of 47 patients with carotid bruits and in 50 (12.5%) of 400 patients without them. The incidence of carotid calcification in the former group was 3.4 times that in the latter (p less than 0.01), although the incidences of hypertension and glucose intolerance were not related to the presence or absence of carotid bruits. A history of cerebral bleeding or infarction was found in 19 (23.2%) of 82 patients with carotid bruits, as compared with 64 (3.8%) of 1,695 patients without them (p less than 0.01). However, the location of the cerebrovascular lesions did not necessarily correlate with the laterality of the carotid bruits. These results indicate that patients with carotid bruits show an increased risk of stroke and that these bruits are a general and non-focal sign of severe atherosclerotic cerebrovascular disease.