Giant intracranial aneurysms are frequently observed as incidental findings on CT and angiograms obtained for purposes other than subarachnoid hemorrhage, such as slowly evolving nerve palsy or hemiparesis. Since giant aneurysms often thrombose, the CT scan may demonstrate a larger aneurysmal volume than the angiogram. This paper presents CT and angiogram findings in cerebral aneurysms with a diameter of 25 mm-60 mm. The discussion covers: sort of aneurysm (congenital, arteriosclerotic); type and degree of thrombosis; long-term results after spontaneous thrombosis; and CT examination after using epsilon-aminocaproic acid.