The trial randomise patients with asymptomatic carotid artery narrowing in whom prompt physical intervention is thought to be needed, but there there is still substantial uncertainty shared by patient and doctor about whether surgery or stenting is the more appropriate choice.

The study is looking at immediate risks (within one month)and at long term benefits

Inclusion Criteria:

• Carotid artery stenosis detectable by duplex ultrasound, with no ipsilateral carotid territory symptoms(or none for some months) and no previous procedure done on it, which might well need procedural treatment now with CEA or CAS.
• Already started any appropriate medical treatment (eg, statin, aspirin etc), and already recovered from any necessary coronary procedures (eg, CABG)
• Patient seems fit and willing for follow-up in person (at 1 month) and by annual letter (for at least 5 years)
• Investigations show that both procedures (CEA and CAS) appear to be practicable and appropriate
• Some type of angiography (eg, MRA or CTA) has already been done that has shown that CEA and CAS would both be anatomically practicable.
• Doctor and patient both substantially uncertain about whether to treat with CEA or CAS, and the doctor sees no clear indication/contra-indication for either procedure

Exclusion Criteria:

• Small likelihood of worthwhile benefit (eg, very low risk of stroke because stenosis is very minor, or major co-morbidity or life-threatening disease, such as advanced cancer)
• Unsuitable for one or other procedure (eg, stenosis at carotid siphon that is inaccessible for CEA, or complex vasculature below the stenosis that would hinder CAS, or patient unfit for major surgery)