To investigate therapeutic strategies for hepatoma, it is necessary to have a reproducible animal model with a tumor growth pattern allowing accurate assessment of results. Many techniques of intrahepatic tumor implantation (IHTI) have been devised for intrahepatic tumor models. Most of them, however, have the disadvantage of high rates of artificial tumor dissemination during tumor implantation, which interferes with the evaluation of therapy. To overcome this problem, we have developed a technique of IHTI in which a piece of Gelfoam is placed into a small incision in the liver for the purpose of both hemostasis and formation of a tension-free pocket to accept the tumor implant. In 583 ACI rats receiving IHTI with Morris hepatoma 3924A, the tumor take rate was 100%. Resembling the natural course of human hepatoma, the implanted tumor grows locally early in the course of disease and eventually invades the surrounding organs causing ascites and also metastasizes to the lung. Liver microangiography demonstrated that the tumor received blood supply mainly from the hepatic artery. This IHTI technique was also compared to two other methods of IHTI: insertion of fragments without using Gelfoam and implantation with a tumor cell suspension. A significantly lower rate of early lung metastases was achieved with our technique (0%) in comparison with other two techniques (41 and 80%). We conclude that this rat liver cancer model is reproducible and allows efficient evaluation of treatment modalities for liver cancer without interference from tumor at undesirable sites.