Detachable silicone rubber balloons, which do not require an outer catheter to effect detachment, were used to close carotid-cavernous fistulas in 10 patients. Closure was effective in nine of 10 patients. The internal carotid artery was intentionally occluded in two patients. The procedure resulted in inadvertent occlusion of the internal carotid artery in three patients. Follow-up studies showed no recurrence of the fistula; nor did any permanent neurologic deficits develop as a result of the procedure. The balloon catheter system and techniques of introduction are discussed in detail. The system is compared with other silicone and latex balloon systems that require a coaxial catheter for detachment. Technical and clinical problems are illustrated.