In 168 patients with ruptured intracranial aneurysms, the pathology of intracranial hemorrhage visualized on CT was analyzed. Blood in the subarachnoid space could be visualized in 95% of cases within three days after SAH and 75% of 106 cases within two weeks after SAH. In one case blood clot in the subarachnoid space visible up to 13 days after SAH. Concerning the cases within two weeks after the bleeding, intracerebral hematomas were observed in 36% of anterior cerebral aneurysms and middle cerebral aneurysms, 16% of internal carotid aneurysms and none of vetebro-basilar aneurysms. The incidence of the intraventricular hemorrhage was as follows; vertebro-basilar, 44%; anterior cerebral, 38%; internal carotid, 28%; middle cerebral, 12%. On the basis of the pattern of distribution of extravasated blood the location of the ruptured aneurysm was properly predicted in 58% of anterior cerebral, 81% of middle cerebral, 58% of internal carotid and 30% of vertebro-basilar. Especially CT could contribute to predict which aneurysm has ruptured in patients with multiple aneurysms. It was possible to localize the site of bleeding in 11 out of 12 CT positive cases. The development of intracranial hemorrhage demonstrated by CT well correlated with the clinical grading of the patients and the clinical outcome. Patients merely showing subarachnoid hemorrhage were more likely to have good neurological grades, but ones showing complicated intracerebral hematomas and intraventricular hemorrhage had poor neurological grades at the time of the scan. The findings of extensive subarachnoid clot, which were followed by severe vasospasm, and marked intraventricular hemorrhage, usually correlated with poor prognosis. These pathology recognizable on CT was very helpful in determination of the timing of surgery and management of such patients. In conclusion CT is of great value in the examination of SAH when performed in the acute stage and should be the initial examination followed by angiography.