Experimental cervical carotid aneurysms in dogs are obliterated with isobutyl-cyanoacrylate ( IBCA ) injected under direct vision into the aneurysm. Reflux of IBCA into the artery was prevented by inflating either a latex or a Silastic balloon in the carotid artery at the level of the neck of the aneurysm. This balloon was introduced through a catheter advanced into the common carotid artery by femoral catheterization. The Silastic balloon was found to be much more effective than the latex balloon in preventing spillage of IBCA into the lumen.