\s=b\We report a case of an asymptomatic posttraumatic aneurysm of the internal carotid artery presenting in the sphenoidal and ethmoidal sinuses. Our initial clinical and radiographic diagnosis indicated a mucocele. There were two reasons for this. First, Maurer's triad of traumatic internal carotid aneurysm was not seen, since neither epistaxis nor visual disorder was present, and fracture was not evident on tomography or computed tomographic scans. Second, no symptoms or abnormalities were found in the sequential neurosurgical evaluations for a period of about six years after the head trauma. The successful results we have obtained in this case are attributable to localization by intraoperative arteriography and to hemostasis by electrothrombotic coagulation within the aneurysm alone, preserving internal carotid artery flow. A high index of suspicion preoperatively, with arteriography as indicated, may facilitate management of these cases, which are likely to become more frequent as medical advances produce more survivors of major head trauma.