PURPOSE: To evaluate therapeutic effect according to embolic materials, and the usefulness of transcatheter arterial embolization (TAE) in the treatment of pseudoaneurysm and aneurysm. MATERIALS AND METHODS: We evaluated 12 patients who since 1987 had suffered arterial pseudoaneurysm or aneurysm. Ten were males and two were females, and their ages ranged from 10 months to 67 years (mean 34 years). The arteries involved were the superficial temporal (n=3), the renal (n=3), the hepatic (n=2), the gastroduodenal (n=2), the persistent sciatic (n=1), and the superior gluteal artery (n=1). All patients underwent diagnostic arteriography and TAE with gelfoam particles, coil, and detachable balloon, or a combination of these. Follow-up, of between three and 74 months duration, involved computed tomography, angiography, ultrasound, and the evaluation of clinical symptoms. RESULTS: All patients were treated successfully with TAE and there was no recurrence during the follow-up. Seven patients (58.3%) were treated only coils; the site of their aneurysm or pseudoaneurysm was the superficial temporal (n=2), the renal (n=2), the gastroduodenal (n=2), or the superior gluteal artery (n=1). Four patients (33.3%) with a small pseudoaneuysm arising from the distal branch of a small artery-the hepatic (n=2), the superficial temporal (n=1), or the renal (n=1)-were treated with gelfoam particles, and a pseudoaneurysm of the hepatic artery too small for the insertion of a coil was embolized completely with gelfoam particles. A detachable balloon was used in one case with a huge pseudoaneurysm arising from the persistent sciatic artery, in which embolization with a large coil was not effective. CONCLUSION: TAE is safe and effective in the treatment of arterial pseudoaneurysm and aneurysm. Coil was the preferred material, but for a small pseudoaneurysm arising from the distal branch of a small artery, gelfoam was preferred . For the embolization of a huge pseudoaneurysm, a adtachable balloon was useful.