An aneurysm is a focal abnormal dilatation of a blood vessel. Cerebral artery aneurysms a true aneurysms mostly located near the skull base. They may present with acute subarachnoid hemorrhage (SAH), but can also be found incidentally on MRI or CT. As many as 20% of patients with subarachnoid hemorrhage have a positive family history. Multiple cerebral artery aneurysms are present in 20%. In SAH, invasive treatment, either surgical or inventional, is always indicated, because of the high mortality of a second hemorrhage. The work-up must include a selective four-vessel catheter angiography of the carotid and vertebral arteries with compression tests. CT angiography is probably the best non-invasive imaging modality in cerebral aneurysms1.