A 40-year-old man was admitted to our hospital suffering from abdominal pain. He revealed marked splenomegaly, lymphadenopathy and pancytopenia. Lymph node biopsy showed diffuse proliferation of medium to large atypical lymphoid cells. Immunohistochemically the cells were positive for T-cell markers. He was diagnosed as having peripheral T cell lymphoma (PTCL) with involvement of the spleen and bone marrow. Because of refractoriness to combination chemotherapies and splenic irradiation, we performed allogeneic peripheral blood stem cell transplantation from an HLA-identical sister. Conditioning was consisted of conventional doses of total body irradiation and cyclophosphamide, and GVHD prophylaxis was performed with cyclosporine and methotrexate. After the patient developed grade III graft-versus-host disease, his splenomegaly improved dramatically. Although the effectiveness of allogeneic hematopoietic cell transplantation in the treatment of malignant lymphoma is controversial, we should consider this as a second-line therapy to refractory subsets of PTCL.