Stroke is the fourth leading cause of death in the United States.1 Each year nearly 800鈥�000 people have a stroke, 600鈥�000 for the first time.1 Atherosclerotic narrowing of the internal carotid arteries鈥攃arotid artery stenosis (CAS)鈥攊s an important cause of stroke.2 Ninety percent of all strokes are ischemic1 and, of these, 10% are caused by large artery stenosis.3 CAS is initially asymptomatic, with its first manifestation frequently transient ischemic attack or stroke.2 A meta-analysis of international studies suggested a prevalence of asymptomatic CAS of at least 50% (moderate stenosis) in 4.2% of the general population, increasing with age to 7% of women and 12% of men older than 70 years.4 However, most studies suggest a higher 5-year risk of carotid territory ischemic stroke in individuals with severe stenosis (鈮�70% narrowing), a degree present in only 0.5% to 1% of US cohorts.3