Established cancer in the liver can, in selected patients who have a good arterial circulation in these tumors, be effectively treated by intrahepatic artery radioactive yttrium-90 resin microspheres. Even in unselected patients treated in the last five years by the author, 17 of 25 patients treated have had good objective regression of cancers, improvement of symptoms and prolongation of life. Treatment is relatively simple and associated with few side effects. For adjuvant therapy of colon cancer having positive nodes (Dukes C), internal radiation therapy of the liver is best done with Phosphorus-32 Colloid passed through the circulation of the gut to be effectively and homogeneously trapped by the Kupffer cells of the liver. Four such patients have been subjected to a pilot study--three of the four are doing well without significant side effects and no evidence of liver cancer after two years. When the fourth died of brain metastases, he too had less liver cancer than would be expected.