PTLD include a range of lymphoid diseases that carry a very poor prognosis. We analyzed the incidence, response to treatment and patient and graft survival after PTLD diagnosis in 590 consecutive cadaveric RT. PTLD incidence was 2.3% (14/590). 71% were males. Age x: 44.5y.(21-66y). Follow-up x: 6.3y.(3m-18y). PTLDs were classified as: Group I: 'early lesion': 1pat. Group II: polymorphic lymphoma: 2 pats. Group III: monomorphic lymphoma: 9 pats [7 non-Hodgkin's lymphoma (NHL), and 2 Burkitt lymphoma (BL)] and Group IV: 'other': 2 Hodgkin lymphoma (HL). Interval from RT to diagnosis x: 8.7y (4m-21y). Only 14% occurred <1 year post RT. HCV was positive in 4 pats, Epstein-Barr virus (EBV) serology was positive in 8 out of 9 pats tested. CD20 positivity was found in 8 out fo 10 pats tested. CMV was present in 2. EBV in tumor cells assessed by PCR or 'in situ' hybridization, was found in 10 out of 13 pats tested. (not found in 2 BL and 1 NHL). Treatment: Group I: immunosuppression reduction (ISR). Group II: ISR plus acyclovir in one pat. IS withdrawal plus anti-CD20 in the second one. Group III: withdrawal or ISR plus chemotherapy and/or surgery in all but two pats that were treated with 4 anti-CD20 doses. Group IV: IS withdrawal plus chemotherapy. Complete response was achieved in 10 pats (71%), with recurrence in two cases. Five pats returned to dialysis at an average of 4.1y (11m-9y) post diagnosis. Three pats died: 1 HL and both BL. Complications: pneumocistis carinii pneumonia 1 pat, heart failure due to adriamicyne and salmonella sepsis 1 pat and 1 pat with a cerebral mycotic aneurism. Our PTLD incidence is 2.3%, similar to that reported. Long-term cumulative patient survival is 79%, much higher than reported, and 64% maintain their allograft functioning. An aggressive treatment according to extension, histology and location is mandatory. The systematic use of prophylactic antimicrobial therapy, hematopoietic growth factors immediately after the beginning of chemotherapy and the fine dose adjustement of these drugs are the main clues for improving the results and minimize the risks.