A 33-years-old man was diagnosed as having undifferentiated carcinoma presenting with right neck lymphadenopathy in December 2000. He obtained complete remission (CR) following chemotherapy, radiation and lymphadenectomy on the right neck. He had multiple para-aorta lymphadenopathy and splenomegaly in December 2001. An open-abdominal lymph node biopsy was performed from which a diagnosis of anaplastic large cell lymphoma was made. CR was achieved with biweekly CHOP, however, the patient suffered from a relapse twice. He underwent allogeneic peripheral blood stem cell transplantation (PBSCT) from his HLA-matched sister while in non-CR in November 2002. Engraftment was achieved on day 14, and at the same time, complete chimerism was confirmed. Acute grade III graft-versus-host disease (GVHD) developed and was controlled with cyclosporine A and prednisolone. Extensive chronic GVHD was subsequently observed and required systemic immunosuppression. His condition returned to CR after the PBSCT and he sustained complete chimerism. He suddenly died of fulminant thrombotic microangiopathy seven months after the PBSCT. The tumor cells were ALK-positive, CD30-negative and JH rearrangement was detected, and were therefore classified as diffuse large B-cell lymphoma with expression of ALK according to the WHO classification, though they differed from this subtype in some points. Although this case was refractory for chemotherapy with a complex karyotype, the graft-versus-lymphoma effect might have contributed to the sustained CR following the PBSCT.