MUCH EMPHASIS has recently been placed on the role of the extracranial cerebral circulation in the production of cerebral infarcts. The importance of the carotid and vertebral arteries in the neck has been stressed by numerous authors working in diverse disciplines.1-4 This activity has occasionally tended to obscure and even to diminish attention to the importance of intracranial arterial disease, specifically atherosclerotic thrombosis, in the pathogenesis of encephalomalacia. One popular and authoritative textbook of neurology in its most recent edition contains the following statements: "It was formerly thought that most cases of cerebral infarctions were due to thrombosis of the trunk or branches of the three main cerebral arteries in the substance of the brain or in their intracranial portion. Necropsy studies, however, failed to show occlusion of these vessels."5 In another study6 the author has examined the problem with dissections of the intracranial and extracranial arterial