An improved treatment method for hepatic malignancies with yttrium-90 incorporated into the matrix of glass microspheres was evaluated prospectively. Fifteen patients with 12 metastatic colorectal cancers, one carcinoid, one islet cell tumor, and one hepatoma were treated with three dose levels: 5,000 cGy (5,000 rad), ten patients; 7,500 cGy (7,500 rad), three patients; and 10,000 cGy (10,000 rad), two patients. Mean follow-up was 7 months (range, 2-12 months). Stable disease in the liver was seen in ten patients, four of whom had concurrent progression of extrahepatic disease, which resulted in two deaths. Two additional deaths were not directly related to the malignant process. Progression of liver disease was found in five patients, with three deaths occurring at 7-8 months. No procedural, hematologic, or pulmonary complications occurred. Late gastroduodenal ulceration occurred at 6-8 weeks in three patients who had histories of chronic alcohol abuse. This method of therapy seems to be feasible and efficient. Caution is necessary with high doses or with patients with a history of or predisposition to gastroduodenal ulcers.