Renal transplant recipients are 2-4 times more likely to develop tumors than the general population, the risks being particularly increased for skin cancer, lymphoma and renal cell carcinoma. The increased incidence of malignancies has been attributed to the immunosuppressive therapy which results in impaired immune surveillance for malignant transformations as well as increased susceptibility for oncogenic viruses. This is particularly highlighted by the role of primary infection with Epstein-Barr virus (EBV) in post-transplantation lymphomas. However, renal chronic kidney disease itself is associated with an increased risk especially for renal and bladder tumors. There are also differences between immunosuppressive agents concerning tumor risk. The increased incidences of certain tumors as well as the associated risk factors have implications regarding tumor prevention, screening and treatment.