Long-term complications of continuous immunosuppression still remain a serious threat and are currently drawing the attention of transplant physicians. Wimmer et al. show that malignancy occurs approximately fourfold more frequently in renal-transplant recipients than in a normal control population. Besides immunosuppression, viruses probably play an important oncogenic role in transplant recipients. The retrospective analysis by Wimmer et al. suggests that mTOR inhibitors and interleukin-2 receptor antibodies are promising immunosuppressive drugs to reduce the risk of cancer after transplantation. These preliminary results must be confirmed in large, prospective, randomized, controlled trials, with long follow-up, designed to evaluate the incidence of de novo malignancy in transplant recipients.