Thirty-two French transplant centers participated in the study of lymphoproliferative disease (LPD) confined to the renal allograft. For the period from 1952 to February 1993, 16 cases were recognized from 16,755 renal transplant recipients. The mean age of the patients was 44 years (range 19-67 years). Fourteen of these recipients received anti-lymphocyte globulin as induction therapy and 13 received cyclosporine as their maintenance immunosuppressive treatment. Acute rejection was reported in 9 cases and was treated with methylprednisolone in 6 cases and with mono- or polyclonal antibodies for 3 episodes. The mean interval from transplantation to development of LPD was 14 months (range, 1-144 months). Most of the patient (12/15) showed symptoms. Renal failure was noted in 7 recipients. Renal ultrasound demonstrated hydronephrosis in 4 cases, a hilar mass in 5 cases, a mass lesion within the graft in 2 cases. Pathological examination showed a high grade malignant lymphoma with extensive necrosis and atypical large cells. Immunohistochemical study was consistent with B-cell lymphoma in all of the 8 cases analyzed and monotypia was noted in 4 cases. The presence of Epstein-Barr virus genome in the LPD was demonstrated in 5 of the 6 cases studied. Nine patients were managed with discontinuation of immunosuppression and transplant nephrectomies. Four patients died. The remaining recipients are alive with no evidence of recurrence after 25 months (range 3-68 months).