This report describes the analysis of 216 CT pictures of 85 patients with ruptured aneurysms which consist of 29 anterior communicating, 27 internal carotid, 27 middle cerebral and 2 basilar arterial aneurysms, including 18 cases with multiple aneurysms. The intervals between CT scanning and the last subarachnoid hemorrhage were various from 6 hours to 4 months. The first CT scanning was made in 40 cases within 3 days, in 54 cases within 7 days and in 11 cases more than one month after the hemorrhage. CT findings showed no abnormality in 9 patients who were classified as Grade I (Hunt and Kosnik) and examined more than 2 weeks after the subarachnoid hemorrhage. Seventy-six patients had some abnormal findings in the first CT scans, which were 55 cases of subarachnoid clot, 16 cases of intracerebral hematoma, 24 cases of intraventricular clot, 16 cases of low density suggesting brain edema or softening and 42 cases of ventricular enlargement. There was a good correlation between CT findings and clinical grade of Hunt and Kosnik. In Grade I and II, abnormal findings other than subarachnoid clot were seldom seen. Iin Grade III, there were intracerebral hematoma (20%), low density (20%) and frequent ventricular dilatation; in Grade IV, massive intracerebral hematoma (80%); in Grade V, massive intracerebral hematoma and ventricular tamponade with blood clot; in Grade Ia, moderate ventricular dilatation and/or diffuse cerebral infarction. Cerebral vasospasm could be anticipated by CT pictures because it occurred frequently in the patients with massive and long-standing subarachnoid blood clot. The determination of the side and location of the ruptured aneurysm was possible in 82% of the patients who had subarachnoid clot, intracerebral hematoma or low density. This is useful to decide the side of the first angiography and the aneurysm to be approached at first in the cases of multiple aneurysms.