Malignancies are one of the major causes of morbidity and mortality in transplant patients. The incidence is progressively increasing either because of the increased age transplant patients and the increase of immunosuppressive therapy or the increased follow-up range post-transplantation. The main causes of increased tumor incidence in transplant patients with respect to the general population are the reduced immunosurveillance and the high incidence of infections due to oncogenic viruses. This problem might become more and more serious in the near future due to the introduction of new immunosuppressive strategies that significantly extend allograft survival. A case of ovarian cancer in a kidney transplant patient is described. Attention is focused on the potential dual role of immunosuppressive therapy in the development of malignancies in transplant patients.