The estimated prevalence of asymptomatic severe CAS (≥70%) in the general adult population ranges from 0% to 3.1%, with a point estimate of 0.9% for persons older than 60 years (calculated from data in the meta-analysis by de Weerd and colleagues ). This includes persons with total, asymptomatic carotid artery occlusion and those with hemodynamically significant tandem intracranial disease who would not be candidates for carotid intervention. After assuming a relative risk of 1.8 associated with asymptomatic CAS (calculated from data from the Cardiovascular Health Study; 0.5% of 5441 persons had CAS ≥70%, among whom 5% had ipsilateral stroke over 5 years, compared with 2.0% of those with CAS <70% ), the population-attributable risk (PAR) for stroke related to asymptomatic CAS is approximately 0.7%. This is dwarfed by other risk factors, such as hypertension (PAR >95%), atrial fibrillation (PAR, 1.5% to 24%, depending on age and other risk factors), cigarette smoking (PAR, 12% to 14%), and hyperlipidemia (PAR, approximately 9%) (2). The prevalence of asymptomatic CAS would need to be 14 times greater than the 0.9% estimate to reach a PAR for stroke similar to hyperlipidemia. As the U.S. Preventive Services Task Force mentioned, there is no validated risk-stratification tool that can reliably identify a subpopulation of persons with a prevalence of asymptomatic CAS approaching this level (4).