As the model of an anti-cancer agent acting at DNA synthesizing phase, BrdU was infused for metastatic liver cancers into the portal vein and/or the hepatic artery. After administration, the liver tumors were resected, and immunohistochemical staining was performed using anti-BrdU monoclonal antibody. Two of 6 portal group tumors were stained. All 4 arterial and 3 arterio-portal group tumors were stained. Therefore, it was proved that metastatic liver tumors had both arterial and portal blood supply. But areas to which BrdU was delivered were only peripheral, and the inmost area was 2 mm from the tumor surface. After the intra-arterial infusion of BrdU suspended in lipiodol, the delivery of BrdU was highly enhanced and 4 of 6 tumors were stained even to the deepest areas. However, one tumor of which the major part was necrotic and one tumor which produced mutin were not stained at all. It was interesting that after intra-arterial administration of BrdU suspended in lipiodol, BrdU was also found in the cytoplasm of normal liver cells.