46 patients (aged 13 to 40 years) suffering from ischaemic cerebrovascular disease were investigated by means of complete 4-vessel angiography. 40 of these patients were re-examined after a mean follow-up period of 57 months. The aim of the study was to investigate possible connections between the angiographic data and the clinical condition some years later. In the 37 patients who were not subjected to surgical treatment prognosis was not significantly different in cases with, and those without stenoses/occlusions in the craniocervical vessels. However, patients suffering from severe stenoses/occlusions had a significantly worse prognosis than patients with stenoses of a mild degree. The clinical course in patients with stenoses/occlusions localized in the vertebro-basilar system was significantly more favourable than the course of the disease in patients with similar changes in the carotid system. There was a trend towards a worse clinical picture at the end of the follow-up period in cases with degenerative alterations in the small intracranial arteries. The difference in prognostic value of cerebral 4-vessel angiography in cases of stroke in the young, as opposed to the findings in older patients is discussed.