The extent of carotid atherosclerosis evaluated by B-mode real-time ultrasound and the presence of bruits established by carotid phonoangiography were determined in 1,107 patients. Unilateral bruit was associated with increased atherosclerosis compared with no bruit (p less than or equal to 0.0001). However, there was no association between laterality of the bruit and the degree of atherosclerosis (p = 0.66). There was marginal evidence that patients with bilateral bruits had more severe atherosclerosis than patients with unilateral bruit (p = 0.046). The relation between bruit and atherosclerosis categorized by B-mode ultrasound was not sufficient to reliably predict the presence or absence of disease in an individual patient, though the presence of a bruit should be viewed as a risk factor for, or an indicator of, increased risk of systemic atherosclerosis.