Post-transplant lymphoproliferative disorder (PTLD) is a known complication of both solid organ transplantation and allogeneic bone marrow transplantation (BMT) but is rarely seen following autologous BMT. We report the case of a 45 year-old female who developed Burkitt's lymphoma eight years after a renal allograft. This PTLD was found to have lambda light chain restriction, contained del(8)(q24) and add(14)(q32), and was negative for EBV on immunohistochemical and DNA-based PCR analyses. Immunoglobulin heavy chain (IgH) PCR studies revealed a prominent clonal rearrangement. She responded to intravenous cyclophosphamide and proceeded to high-dose chemoradiotherapy and mafosfamide-purged autologous BMT. Thirty-nine days post-BMT she presented with cough and fever and developed hepatic dysfunction; abnormal lymphoplasmacytoid cells were noted in the peripheral blood. Investigations revealed kappa light chain restriction, an oligoclonal IgH rearrangement, a normal karyotype and PCR studies for EBV were positive, consistent with a clinically and biologically distinct PTLD. She initially improved following discontinuation of immunosuppression, but then deteriorated abruptly and died 58 days post-BMT. It is likely that the two separate episodes of PTLD in this patient, one of which was atypical, arose as a result of both the chronic use of cyclosporine and the impairment of cell-mediated immunity associated with autologous BMT. The sequence of events in this patient should contribute to a better understanding of late-onset, EBV-negative PTLD.