According to the analysis of the Collaborative Transplant Study (CTS), the incidence of renal carcinoma in patients with renal transplantation as well as with heart transplantation is significantly increased at any given patient age. The cumulative incidence 10 years after kidney transplantation is 185 per 100,000 patients in children below the age of 19 years at the time of transplantation. Age and immunosuppressive treatment seem to be the major risk factors. The majority of cancers develop within the native kidneys. Chronic transplant nephropathy and accelerated senescence may be further risk factors for the development of cancer within a kidney transplant. Growth hormone (GH) treatment could not be identified as an additional risk factor.