Repeat CT scanning and cerebral angiography has been performed in 68 consecutive patients with subarachnoid hemorrhage. Blood in the subarachnoid cisterns could be discerned in 27 of 32 patients provided the examination was performed within 2 days of the bleeding. The distribution of cisternal blood can be identified which, in combination with the localization of a possible intracerebral hematoma, yields a rather good predictability as to the site of the ruptured aneurysm. The subsequent angiography can thus be directed to the relevant vessel in most cases. Repeat CT scanning can replace angiography in the evaluation of patients with deterioration of the clinical condition.