We performed Transcranial Doppler Monitoring to detect microembolic signals (MES) in 47 patients with moderate (30%-69%) carotid stenosis proven by selective angiography. We compared the occurrence of MES with the clinical characteristics of stenosis (symptomatic or asymptomatic) and the angiographic plaque features (nonulcerated, deep ulceration, superficial ulceration, ulceration with flap, or ulceration without flap). For these cases there was no indication for endarterectomy, nevertheless we thought it would be useful to identify risk subgroups that might benefit from surgical treatment. MES were detected in 17.9% of the stenoses with a prevalence (p <. 01) in symptomatic cases (25%) compared to asymptomatic cases (14. 3%). There was a significant correlation of MES with plaque ulceration (p <.01) and particularly with ulceration without flap (p <.01). No difference between deep and superficial ulceration was observed. The availability of prospective data on this topic might be useful to select subgroups of patients with moderate carotid stenosis at risk for embolism.