The cerebral scans of 365 patients with the stroke syndrome were reviewed retrospectively over a 30-month period. Positive static studies occurred in 140 patients )38%), of which 73 (52%) had an associated reduction of flow to the affected hemisphere on the dynamic study. Positive dynamic studies alone accurred in 69 patients (19%), increasing the positive yield by 50%. Dynamic studies also differentiate extracranial (carotid) occlusion from intracranial vascular occlusion, and may contribute to prognosis and management. Infarction in the middle cerebral artery territory is five times as common as infarction in any other arterial territory. An unexpected finding was the high incidence (5%) of watershed infarctions. These are more common than posterior cerebral artery strokes (4%), and anterior cerebral artery strokes (1%). When patients with vertebrobasilar and lacunar strokes, and those scanned within one week or after six weeks from the onset of symptoms are excluded, the positive yield was 54% for static studies, and 67% over all.