We describe a patient with progressive natural killer (NK) cell lymphoma who was treated successfully with allogeneic peripheral blood stem cell transplantation (allo-PBSCT) followed by early cyclosporine (CsA) tapering and donor leukocyte infusion (DLI). Because the disease showed early resistance to conventional chemoradiotherapy, we performed high-dose chemotherapy followed by allo-PBSCT. After achieving hematologic engraftment, the patient underwent early tapering of CsA and DLI in an attempt to induce a graft-versus-lymphoma effect. Although the disease was in a progressive state at the time of transplantation, complete remission was obtained after allo-PBSCT. As of this report, the patient has been well for more than 2 years.