Gene therapy is a new therapeutic option for liver tumors which has been evaluated in animal models. The liver has characteristic features particularly interesting for gene transfer. Because of the rapid tumor growth within a quiescent parenchyma, retroviral transfer could express selective tropism. Temporary anatomic vascular exclusion would allow selective perfusion of the liver and avoid extrahepatic diffusion of the gene therapy. The early results have been promising in the animal. Clinical studies are currently under way in patients with liver metastasis from colorectal cancer.