This report reviews 41 cases of traumatic cerebral aneurysms, including four cases of our own which are presented in detail. They may follow penetrating or closed head injury, and are usually associated with significant additional intracranial damage. Almost half of the patients presented with a delayed subarachnoid hemorrhage within three weeks of the initial head injury, defining an important neurological syndrome. Those patients whose post-traumatic aneurysms have been surgically obliterated have an associated mortality which is half that of patients treated by nonsurgical methods.