The autors reported a giant aneurysm in the cavernous portion of the internal carotid artery which occurred after head trauma. The patient was a 24 year old man who had suffered massive epistaxis with hyoptension about 25 days after a traffic accident. On plain skull X-ray, there was evidence of a basal skull fracture and a linear fracture at the right frontotemporal area. The computed tomographic scan revealed round, well enhanced density in the sellar region. During a reattack of massive epistaxis, emergency carotid angiography showed a right cavernous-internal carotid artery aneurysm with a small extravasation of dye into the sphenoid sinus.