Endovascular use of detachable balloons has revolutionized the management of carotid-cavernous fistulas so that the goals of angiographic elimination of fistula and preservation of carotid patency can usually be achieved nonsurgically. Certain circumstances of flow dynamics and anatomy, however, make an endovascular approach difficult for even an experienced interventional neuroradiologist. Fistulas involving the posterior carotid wall at its proximal cavernous entry and the anterior carotid wall in its initial horizontal intracavernous segment, as well as very low flow fistulas at other sites, have posed particular problems. Three patients with such traumatic fistulas whose endovascular treatment failed were managed by the direct transdural introduction of balloons. Intraoperative angiography was accomplished with open internal carotid artery (ICA) catheterization and the use of a portable C-arm with a 6-in. image intensifier. After temporal craniectomy and subtemporal exposure, the course of the cavernous ICA was mapped out with spinal needles and the site of the fistula was localized by intraoperative angiography. An incision was then made in the lateral wall of the cavernous sinus, and latex balloons were manually introduced via a 7 French introducer sheath. The balloons were inflated under angiographic control and detached when the fistula was obliterated. This simple technique was initially successful in three patients; the fistula was eliminated with preservation of carotid patency. One patient suffered a recurrence of his fistula 2 months postoperatively while lifting weights, and one patient developed a new 3rd nerve palsy after operation.