The establishment of liver metastasis from gastrointestinal tumor is mainly considered to be via the portal vein, but its precise mechanism is still unknown. The purpose of this study is to evaluate the significance-of 'streamline' phenomena in liver metastasis of gastrointestinal tumor by means of an experimental model. An animal model for the metastatic liver tumor was made in the Donryu rat. Five million cells of AH-66 strain, alpha-fetoprotein (AFP) producing hepatoma cells maintained as an ascites type strain, were administered via portal vein. The superior mesenteric vein (group A), the inferior mesenteric vein (group B) and the splenic vein (group C) were used as the sites of injection. In every group, serum AFP levels were elevated after administration of AH-66 cells and no significant differences were revealed between each group. In the pathological specimens of the liver taken after 7 days, many tumorous lesions were seen microscopically with islet formations, but no definitive difference was seen in each lobe. The serum AFP concentration in group A was significantly higher than that in group C. The tissue AFP concentrations of the right lobe were significantly higher than those of the left in groups A and B, but significantly lower than those of the left lobe in group C. The results indicate that the distribution and proliferation of tumor cells administered via portal vein differed depending upon the site of tumor injection in accordance with the 'streamline' phenomena.