A suspension of iodized oil and anticancer agent was injected into the portal veins of 20 rats with hepatic carcinoma and of 20 normal rats to observe its distribution in the liver and the effect on cancer tissue and normal cells. Microscopic and transmission electron microscopic examinations were carried out. Oil drops were seen in tumor cell lines, small blood vessels inside the cancer nest, the sinusoids, and the central veins. More oil drops were found in the peripheral parts of the tumor than in the central part. The distal small vessels were embolized with necrotic change of tumor cells and their subordinate normal liver cells. We conclude that portal vein part takes in the blood supply of liver cancer and tumor cell necrosis can be achieved after administration of iodized oil and anticancer agent mixture through the portal vein. Hence transcatheter treatment through the portal vein may be helpful as a supplement to intraarterial treatment of primary liver cancer and transcatheter embolization via the portal vein to reinforce the intraarterial therapy may be recommended. This procedure may cause necrosis of normal liver cells and care must be taken in clinical application.