One hundren patients underwent high-resolution dynamic ultrasound imaging of the carotid bifurcation immediately before cerebral angiography. The examinations were interpreted independently. A positive ultrasound interpretation indicated the presence of moderate to extensive atheromatous plaque, while a negative interpretation indicated normal vessels or minimal atheromatous disease. Ten percent of the ultrasound examinations were technically unsatisfactory. Of the remaining studies, there was satisfactory correlation between ultrasound and angiography in approximately 85% and disagreement in 15%. The majority of ultrasound errors were "false positive" (although these probably represent false-negative angiograms). Although atheromatous disease was accurately detected by ultrasound, stenosis, ulceration, intraluminal thrombus, and vessel occlusion were not reliably identified.