Severe head injury with resultant basilar skull fracture is the most common etiology for traumatic false aneurysm of the cavernous carotid artery and for traumatic carotid-cavernous fistula. We present a case of false aneurysm and fistula that occurred as a complication of sphenoidotomy, fortunately a rare etiology of these two serious problems. Because of the current resurgence of trans-sphenoidal surgery, it is of utmost importance that all neurosurgeons possess an accurate and detailed knowledge of the anatomy of the carotid artery and its intracavernous route.