A 27-year-old man with advanced colon cancer that was resistant to conventional chemoradiotherapies was treated with reduced-intensity allogeneic peripheral blood stem cell transplantation (PBSCT). After obtaining complete donor-type chimerism, there was an apparent graft-versus-tumor effect accompanied by severe hepatic graft-versus-host disease (GVHD) showing hyperbilirubinemia, resulting in a stable disease condition that lasted for 18 months, which had not been seen previously in his previous disease history. The antitumor effect observed in this patient was insuffi cient for the patient to achieve complete remission, because the disease was at an already widespread and treatment-resistant stage. He fi nally died of hepatic failure due to extensive liver GVHD 65 months after the diagnosis of the advanced colon cancer and 29 months after the allogeneic PBSCT. Prospective studies are necessary to achieve better clinical results in patients with advanced colon cancer.