Post-transplant lymphoproliferative disorders (PTLD) are recognized as a devastating complication of organ transplantation. Their occurrence appears to vary according to the transplanted organ and the type and the level of administered immunosuppressive therapy. In kidney transplants the incidence is estimated between 1 and 2%. PTLD represent a clinically and morphologically heterogeneous group of lymphoid proliferations. They have been closely associated with Epstein-Barr virus (EBV), and the spectrum of manifestations after transplantation range from an infectious mononucleosis-like syndrome to more serious polyclonal or monoclonal lymphoproliferation, the treatment of which is not well defined and, relying on immuno- and chemotherapy. Oncogenicity of EBV is not yet completely understood, but may implicate latent viral gene expression of EBNA or LMP as well as Th2 cytokines. Detection and monitoring of EBV induced lymphoid abnormalities are necessary to start early efficient antiviral treatment. Prophylactic antiviral therapy has to be considered.