The temperature curves of 262 patients affected by subarachnoid hemorrhage, including 107 arterial aneurysms, 26 arteriovenous malformations, 42 idiopathic subarachnoid hemorrhages, and 87 cerebral hemorrhages, were observed and classified into three types: Type I: absence of fever; Type II: fever oscillating between 37 degrees and 38 degrees C; and Type III: fever with a plateau between 38 degrees and 39 degrees C beginning on the fifth day at the latest and lasting an average of nine days, with a decline over the next three days. Type III was observed in 3.8% of the patients with arteriovenous malformations, 7% of those with cerebral hemorrhages, and 88.3% of those who had arterial aneurysms with severe angiographic vasospasm associated with delayed ischemic signs. We suggest that the delayed fever is not a simple sign of meningeal syndrome but a sign related to cerebral vasospasm.