Nine cases have been presented in detail to illustrate some of the varied causes of sudden neurological deficit in childhood: arteriovenous malformation, cryptic hamartoma, berry aneurysm, mycotic aneurysm, intraspinal arteriovenous malformation, brain tumor, migraine, arteritis, and multiple sclerosis. The Boston Children's Hospital experience with aneurysms and intracranial arteriovenous malformation has been summarized. It is noteworthy that a cutaneous hemangioma overlay one cranial and one intraspinal arteriovenous malformation. One small but deep cerebral arteriovenous malformation apparently destroyed itself after its second hemorrhage. Not only have multiple sclerosis and a brain tumor mimicked a vascular lesion, but a series of vascular accidents was misdiagnosed first as multiple sclerosis then as a thalamic tumor. The many possible causes of childhood strokes has been thoroughly cataloged in the Report of the Joint Committee for Stroke Facilities in 1973 (11). Children may be more susceptible to strokes because of congenital abnormalities such as congenital heart disease, hemophilia, and sickle cell anemia, or by diseases which more commonly occur in this age group, such as leukemia. The likelihood of brain abscess in cyanotic congenital heart disease is stressed. Arteriographic studies in our series have been safe; however, there have been reports of probable worsening of symptoms in children with multiple cerebral occlusive lesions in the presence of homocystinuria.