Occlusion of the basilar artery is mainly of atherosclerotic origin; embolic occlusion, dissecting aneurysm, trauma and arteritis are less frequent. Pathologic and angiographic findings allow to classify basilar artery occlusions in three types: segmental (superior, medial or inferior), plurisegmental and extensive. The infarcted areas involve brain stem, especially pons and cerebellum, also diencephalon and cerebral hemispheres, in various combinations. Clinically, there is typically a prodromic stage, with transient ischemic attacks (vertigo, headaches, visual disturbances, motor deficit). Few weeks later, a decreased level of consciousness and motor anomalies are the most important signs. A fatal outcome is noted in 85,98 p. 100. Among laboratory examinations, only angiography proves the occlusion: it also shows the arterial supply (carotido-basilar reflux; inter-cerebellar anastomosis). Computed tomography usually eliminates an expanding mass of the posterior fossa. Management is only of general type. Surgical management of carotid arteries stenosis may ameliorate the anastomotic flow.