Atherosclerosis of carotid and vertebrobasilar arteries is a strong risk factor for ischemic stroke, as well as a strong and independent predictor of myocardial infarction and vascular death. Within the past years, the important progress made in the knowledge of carotid atherosclerosis prognosis has contrasted with the lack of studies for vertebral atherosclerosis. In patients with carotid atherosclerosis, the risk of stroke is clearly related to the severity of stenosis and the risk of recurrent ipsilateral stroke is much higher than the risk of a first-ever stroke. Patients with intracranial atherosclerosis seem to carry a high risk of stroke. Therapies for the prevention of vascular events in patients with carotid and vertebrobasilar atherosclerosis include modification of arterial risk factors, antithrombotic therapies and sometimes carotid surgery. When the benefit of surgery is very high for patients with symptomatic severe carotid stenosis, this benefit is small for those with symptomatic moderate or asymptomatic severe carotid stenosis. New medical strategies and the advantages of angioplasty are currently under investigation.