A HEALTHY 72-YEAR-OLD woman was referred to a vascular surgeon after a carotid duplex scan demonstrated elevated velocities in her left internal carotid artery, consistent with an 80% to 99% stenosis. Questioning revealed an absence of symptoms such as extremity numbness or tingling, dysarthria, or amaurosis fugax. She was nonhypertensive and had never used tobacco products. Furthermore, her lipid and serum creatinine levels were within normal range, and there was no family history of atherosclerotic disease. The primary care physician gave her a regimen of one aspirin per day.