An old woman had stroke at age 67. Cerebral CT scan disclosed the low-density lesion with high-density area in the left temporal lobe, but no empty delta sign in the superior sagittal sinus. Thereafter, she had sometimes panic attacks. At the age of 70, she was admitted because of loss of consciousness probably caused by the same attack. On admission, Brain CT scan showed no fresh lesions. During the stay in the hospital, she had an episode of deep vein thrombosis of her left leg. The patient was found to have not only reduced biochemical activity but also low immunological level of AT III. Her nephew had also the low plasma AT III antigen concentration. Transesophageal echocardiography showed no abnormality, but atherosclerotic change at the aortic arch. We speculated that hemorrhagic cerebral infarction in the territory of the branch of middle cerebral artery could be induced by the arterial thrombus which was related to the hypercoagulable state associated with familial AT III deficiency, although the possibility of cardiogenic embolic infarction or of cerebral vein thrombosis could not be ruled out. Familial AT III deficiency is one of the causes of cerebral infarction even in the elderly.