The purpose of the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) is to compare the relatively new procedure of stent-assisted carotid angioplasty (CAS) to the traditional and accepted surgical approach of carotid endarterectomy (CEA) for the treatment of carotid artery stenosis to prevent recurrent strokes in those patients who have had a TIA (transient ischemic attack) or a mild stroke within the past 6 months (symptomatic) and in those patients who have not had any symptoms within the past 6 months (asymptomatic).