In cases of metastatic cancer of the liver in rats, the effect of ligation of the hepatic artery (HAL) or portal vein (PVL) with or without intraportal chemotherapy with Mitomycin C (MMC) was studied in Experiment I. HAL or PVL alone and chemotherapy alone induced only a slight anti-cancer effect. The most striking effect was found in the group treated with HAL plus MMC. PVL plus MMC produced intermediate results. To evaluate which route,via the hepatic artery or portal vein, is more effective for the adjuvant chemotherapy after HAL, Experiment II was conducted on the rats with a minute and/or a rather advanced metastatic cancer of the liver. Chemotherapy with MMC by either route alone and HAL alone did not substantially prolong the survival time, irrespective of the tumor size. HAL plus chemotherapyvia, both routes produced a statistically longer survival time compared with the control, however, better results were obtained by intraarterial chemotherapy. When compared with the two groups treated by the same procedures but at the different times, the earlier treatments produced better results. In the light of the present studies, it can be concluded that if cytocidal drugs with dose independent effects are given in a single bolus, HAL in connection with intra-arterial chemotherapy is a beneficial modality for the treatment of nonresectable liver cancer.