Carotid atherosclerotic disease is a major source for artery to artery embolism. Stroke incidence highly depends on the degree of carotid stenosis. TCD monitoring for embolic signals may help to identify patients at high risk for an impeding stroke. This study was performed to correlate the degree of carotid stenosis with the occurrence of embolic signals and the clinical outcome. We performed a bilateral simultaneous TCD study on 4 patient groups with unilateral atherosclerotic disease: We studied patients with non-stenotic ICA plaques (n = 21), 50-75% ICA stenosis (n = 20), 75-95% stenosis (n = 22), and occlusion (n = 13). Minimum insonation time was 45 minutes. Embolic signals were not detected in the control group and patients with a non-stenotic ICA lesion, but in 10% of the patients with 50-75% stenosis, 22% of the patients with a high grade stenosis and 39% of the patients with an ICA occlusion. There is a high specificity (92%) and rather low sensitivity (29%) of these microemboli for past clinical events. The occurrence of embolic signals correlated (p < 0.005) with a history of stroke, TIA or RIND. Microemboli detection may be a valuable tool to identify high risk patients.