Computed tomography (CT) scans of 49 patients with subarachnoid hemorrhage (SAH) secondary to ruptured aneurysms were reviewed. Subarachnoid blood was detected in 95% when CT was performed within 5 days after the bleeding. Prediction of the site of the ruptured aneurysm from distribution of the cisternal blood varied from 92% for the anterior cerebral artery aneurysms to 70% for the middle cerebral and 47% for the internal carotid artery aneurysms. Following plain CT scans, postcontrast studies were performed in 27 patients. Aneurysms were directly visualized in 8 cases and subarachnoid enhancement was noted in 21. In 3 cases, subarachnoid enhancement made possible a correct diagnosis of SAH in the absence of evidence of cisternal blood on precontrast CT scans.