Abstract
In addition to occlusion of the distal part and branches of the internal carotid artery in two adult patients, angiography revealed a fine vascular network on the convex surface and at the base of the brain, identical with the angiographic picture of `Moyamoya disease'. On the basis of the pathological examinations, the occlusion of the cerebral blood vessels was caused by arteriosclerosis in both cases. The causes and conditions of development of the `Moyamoya' picture are discussed. In the authors' opinion, this is not an independent disease: under the conditions described the characteristic pattern may develop in any type of vascular occlusion as a special form of accessory circulation in the cerebral areas the blood supply of which has been impaired.