The recent European Carotid Surgery Trial (ECST) and North American Symptomatic Carotid Endarterectomy Trial (NASCET) have clearly defined a population who benefit from carotid artery endarterectomy (CAE). However these trials used different criteria to identify > 70% stenosis of the internal carotid artery (ICA). The role of CAE in asymptomatic ICA stenosis has been investigated by the Carotid Artery Stenosis with Asymptomatic Narrowing Operation Versus Aspirin (CASANOVA) study, the Veterans Administration Asymptomatic Carotid Study (VAACS) and the Asymptomatic Carotid Artery Stenosis (ACAS) trials, all of which have design limitations. The Asymptomatic Carotid Stenosis Trial (ACST) is still recruiting patients but until the natural history of asymptomatic ICA disease is understood, the role of surgical intervention will continue to be controversial.