Over a 10-year period, 284 patients underwent 410 embolization procedures because of liver, renal, or bone tumors; gastrointestinal bleeding; systemic or pulmonary arteriovenous malformations; and other miscellaneous lesions. A wide range of particulate and liquid embolic agents were used. The complications were analyzed with respect to the patient's underlying abnormality. Minor complications occurred after 16.3% of procedures, serious complications after 6.6%, and death after 2%. The postembolization syndrome (fever, elevated white blood cell count, and discomfort) was encountered after 42.7% of the procedures, and in 43.7%, no significant adverse reactions were documented. The major complications and deaths were encountered in patients with a serious underlying abnormality in whom no alternative form of treatment was available and who were extremely sick prior to the procedure. When considered in relationship to the natural progress of the disease and the lack of other treatment options, the overall complication rate seems acceptable.