Forty patients with asymptomatic metastatic cancer to the liver discovered at the time of laparotomy were treated by combined intrahepatic arterial chemotherapy and internal irradiation in the form of 90Yttrium microspheres. One group of 25 patients were treated by a catheter inserted at the time of operation and received 100 mCi; of 90Yttrium microspheres and 5-fluorouracil on a continuing basis. They survived an average of 26 mo (varying from 9 to 60 mo). The second series of 15 patients referred after surgery were treated by the percutaneous insertion of the catheter into the hepatic artery and received a bolus of combined chemotherapy consisting of PlatinolTM, Methotrexate, and 5-fluorouracil. They survived an average of 31 mo, which varied from 12 to 60 mo. The dose of 100 mCi of 90Yttrium was well tolerated by the liver. Prospective studies are in progress, limiting the treatment to the internal irradiation to determine its precise role in the overall treatment of metastatic cancer to the liver.