For embolization to be successful, three factors must be addressed: embolic agent selection, clinical application, and technical skill. The major embolic agents used include stainless steel coils, absorbable gelatin pledgets and powder, polyvinyl alcohol foam, ethanol, and glues. Each of these agents acts at different levels in the arterial system; for example, coils are equivalent to surgical ligation and occlude medium to small arteries, whereas liquid agents and the smaller diameter particles occlude at the arteriolar level or the capillary bed. The type of agent selected should also be determined according to clinical application, which includes trauma, tumors, male infertility, impotence, and vascular malformations. It may be better to occlude an artery only temporarily, particularly in trauma patients, and absorbable gelatin material is preferred for this application. Conversely, permanent occlusion of arteries with either ethanol or polyvinyl alcohol foam particles may be necessary in the treatment of tumors. To use embolotherapy effectively, the interventional radiologist must be experienced, familiar with the underlying pathologic processes, and knowledgeable with regard to the role of other specialties in the treatment of the disease process presented.