We report a new treatment for carotid-cavernous fistula. Using a flow-guided, balloon-tipped microcatheter, we catheterize the fistula itself, verify balloon entry into the fistula with fluoroscopy and x-ray films, and then infuse the tissue adhesive isobutyl-2-cyanoacrylate with careful fluoroscopic control. Three patients have had their fistulas occluded, with preservation of flow through the internal carotid artery. This balloon microcatheter allows the radiologist to perform a reversible test occlusion. All three patients had neurological changes during or after the procedure, and in one we inadvertently occluded several distal middle cerebral artery branches without permanent neurological deficit. No patient became blind or developed 3rd, 4th, or 6th nerve palsy from the treatment. This technique seems to have promise as another method for the obliteration of carotid-cavernous fistula.