The effect of continuous arterial infusion against metastatic liver cancer was examined by experimental study using female rabbits and VX2 system. Therapy combining 2 different; anti-cancer drugs was evaluated in this study; one was sequential 5-FU + Methotrexate (MTX) + Leucovorin (LV) therapy and the other was high-dose LV infusion followed by 5-FU infusion. Five or 7 days after inoculation of one million VX2 cells to superior mesenteric artery, a Teflon tube was inserted into the left gastric artery and brought to a point near the hepatic artery. Continuous infusion was achieved for the following 5 days from this catheter using an arterial infusion pump. The result was evaluated by the number of metastatic liver tumors. In the sequential 5-FU + MTX + LV therapy, the number of metastatic liver tumors of continuous arterial infusion group was remarkably smaller than that of the control group and the systemic venous infusion group (p less than 0.01 and p less than 0.001). The concentration of 5-FU was also highest in the continuous arterial infusion group in liver tissue and lowest in other extra hepatic organs. In high-dose LV + 5-FU infusion therapy, the mixed infusion of the LV + 5-FU group has been shown to be the most effective result to date. But since the number of surviving animals is still small, the final result is not yet in. On the other hand, we have the impression that the toxicity of 5-FU is increased by LV in this series, and this must be investigated in our following series of experiments.