Percentage of carotid stenosis and plaque morphology as determined by duplex scanning were correlated with symptoms and CT evidence of infarction in 108 patients. Severity of carotid stenosis less than 49% or greater than 50% narrowing was not associated with an increased risk of ipsilateral symptoms or CT infarction. However, a heterogeneous plaque appearance, suggesting intraplaque hemorrhage, did correlate with ipsilateral cerebral symptoms. Heterogeneous plaque appearance may be a more reliable indication for carotid endarterectomy than a hemodynamically significant stenosis.