Posttransplant lymphoproliferative disorder (PTLD), a well recognized complication of organ transplantation, comprises a wide spectrum of heterogeneous lymphoid proliferations ranging from self-limiting mononucleosis through aggressive monoclonal non-Hodgkin's lymphoma (NHL). There has been marginal success in treating PTLD using a number of treatment modalities, including combination chemotherapy. There have been few reports of the use of high dose chemotherapy with stem cell rescue as a treatment for PTLD. We report a renal allograft recipient who developed PTLD of the diffuse large cleaved B cell, NHL type. Reduction of immunosuppression was initially effective, however the patient relapsed, and was treated successfully with CHOP chemotherapy. Two years later he again relapsed and was treated with high dose melphalan followed by autologous peripheral blood stem cell transplantation (PSCT). The patient has remained in complete remission for 4 years with no major organ toxicities and a functioning renal allograft on minimal immunosuppression. This case illustrates a potential role for high dose chemotherapy with stem cell transplantation for the treatment of PTLD.