In about 5% of all organ (kidney, liver) transplant recipients, malignancies occur as a late complication of the massive immunosuppression. The malignancies are mainly skin cancers, lymphomas and renal carcinomas. This book discusses the possible mechanisms of this type of tumorigenesis and investigates possibilities of prevention - in particular, malignancies of viral origin. The book also discusses a completely new type of carcinogenesis. The work is intended for oncologists, surgeons, nephrologists, hepatologists, virologists and immunologists.