Carotid artery dissection is a major cause of cerebral infarction in the young. The extracranial portion of the internal carotid artery is much more frequently involved than the intracranial portion. In up to 20% of cases it is bilateral or associated with vertebral artery dissection. It is mainly characterised by local signs such as headache or facial pain, Horner's syndrome, lower cranial nerve palsies and pulsatile tinnitus, followed a few hours or days later by signs of cerebral or retinal ischemia. Ultrasound investigations show signs of distal stenosis or occlusion, highly suggestive of dissection, but the best diagnostic tool is presently the association of magnetic resonance imaging (MRI) and MR angiography which tend to replace intra-arterial angiography. The prognosis is highly variable: excellent in cases limited to local signs, but very poor leading to death or major sequelae in about 15% of cases. Various treatments have been suggested but no controlled trial has ever been performed in this condition. Heparin in the acute stage followed by warfarin or aspirin for 3 to 6 months is most commonly used.