We present the case of a comatose patient with acute large infarction of posterior cerebral and cerebellar areas and severe hyperthermia (max. 40.4 degrees C). Angiography demonstrated four-vessel occlusion of the main cerebral arteries, suggesting the possibility that both internal carotid and left vertebral arteries were already occluded and he became unconscious following additional occlusion of the right vertebral artery. Autopsy findings revealed bilateral ischemic damage of the hypothalamus in addition to the above infarct areas. Sudden ischemic involvement of both hypothalamic regions may have caused the extremely high fever in this case.