Posttransplantation lymphoproliferative disorder (PTLD) of T-cell origin has been rarely described in chronically immunosuppressed allograft recipients. We report a case of renal PTLD of a T lineage that occurred shortly after transplantation under a triple-immunosuppressive regimen. Renal graft biopsy performed 58 days posttransplantation showed extensive interstitial infiltrates of polymorphic lymphoid cells, which expressed the UCHL-1 and CD3 markers for T-cell lineage. The clonal nature of the T cells in renal tissue was identified by showing rearrangement of the T-cell receptor gamma chain genes using a polymerase chain reaction (PCR). DNA extracted from the graft biopsy specimen did not show the sequences of human T-cell leukemia virus type 1 (HTLV-1) by PCR. Signals for Epstein-Barr virus (EBV) infection in renal tissue were not shown by in situ hybridization. After the reduction of immunosuppressive therapy, regression of PTLD lesion and development of rejection were shown in the second graft biopsy and graftectomy specimen. The extreme rarity of rapidly developing T-cell PTLD in a renal allograft prompted us to write this report.