The US asymptomatic carotid atherosclerosis study first reported reduction in stroke rate after prophylactic carotid endarterectomy. Four large randomized trials have now been reported suggesting that carotid endarterectomy for asymptomatic disease can prevent stroke. The US Veterans Administration hospitals' trial reported that 4 years after prophylactic carotid endarterectomy patients with asymptomatic carotid stenosis of 50-99% had significantly fewer transient ischemic attacks (TIA) and strokes than controls. The asymptomatic carotid surgery trial (ACST) is the largest vascular trial to date. Trials suggest that selected patients with asymptomatic disease will benefit from carotid endarterectomy. Appropriate screening populations could include patients attending vascular clinics, patients with contralateral symptomatic stenoses or disease in another vascular bed. A more recent study of combined or staged carotid endarterectomy and coronary artery bypass graft (CABG) in patients with asymptomatic carotid disease suggests that the perioperative stroke risk compares favorably with CABG alone.