Recent Russian reports have described the use of balloon occlusion in both the diagnosis and treatment of various pathological processes affecting intracranial vessels. This intraluminal approach has demonstrated successful results in vascular problems such as carotid-cavernous fistulae, arteriovenous malformations, and large inoperable aneurysms. Despite widespread interest in the neurosurgical community, the application of a similar technique in the Western hemisphere has been hindered by lack of an adequate, functional, inflatable apparatus. The authors describe their experience with the prototype of a safe, reliable, detachable balloon. Because of a unique development, the apparatus may be filled with liquid and detached from its parent catheter without subsequent leakage. In order to satisfy variable requirements, balloons are available in several sizes ranging from 0.5 to 4.0 mm in diameter. When fully inflated these devices will hold from 1 to 3 cc of fluid. The authors' study involved 18 dogs with artificially created carotid-jugular fistulae that were visualized by angiography. Under fluoroscopic control, detachment of inflated balloons on the venous side of the defect not only successfully occluded the fistulae but also preserved the arterial vasculature. X-ray films taken several weeks later failed to show any change either in size or position of the inflated devices.