The overall prevalence of post-transplant lymphoproliferative disorder was 1.4% (2.5% in heart, 0.9% in liver and 0.8% in kidney-transplanted patients) and significantly higher in hepatitis C virus positive than in hepatitis C virus negative patients (3.6 % vs 1.2 %; P=0.04). Epstein-Barr virus was present in 10 (77%) out of 13 tumors tested. Two out of three Epstein-Barr virus-negative post-transplant lymphoproliferative disorder developed in hepatitis C virus-positive patients