Among 53 patients with hereditary protein C deficiency belonging to 20 families three women were encountered who, aged 27, 34, and 38 respectively, had had cerebral haemorrhagic infarction, probably due to intracranial venous thrombosis. All three had also had venous thrombosis of the leg and pulmonary embolism either before or after their cerebral infarction. One patient sustained cerebral infarction while receiving an oral contraceptive, but infarction in the two others occurred "spontaneously." One patient also had an intraventricular and subarachnoid haemorrhage during the induction phase of coumarin treatment, which was assumed to have resulted from haemorrhagic infarction of the chorioid plexus, analogous to coumarin provoked haemorrhagic skin necrosis in protein C deficiency. Hereditary protein C deficiency should be considered in young patients with acute or subacute cerebral symptoms, especially if they have a family or personal history of venous thromboembolism.