BACKGROUND Life expectancy after transplantation has improved, and cancer may soon be the leading cause of late death after transplantation. The guidelines of the American and European societies of nephrology and urology have not yet established the optimal frequency for screening for renal cell carcinoma (RCC) of native kidneys in patients who have undergone renal transplantation. OBJECTIVE To evaluate the prevalence, prognosis, and risk factors of RCC in a series of patients followed up for 16 years in our transplantation unit. METHODS Our study is a follow-up observational cohort study conducted in 694 consecutive renal transplant recipients admitted to our institution from July 1991 through July 2007. At our institution, ultrasound studies of the native kidneys were performed every 6 months after renal transplantation. RESULTS In the patient cohort studied, 10 patients developed a renal tumor (1.6% incidence). Three patients died of causes other than recurrence of RCC. Seven patients are alive with no evidence of RCC recurrence or metastatic disease after a mean (range) follow-up of 41 (12-96) months. Acquired cystic kidney disease and dialysis duration were positively associated with development of RCC. CONCLUSIONS The incidence of RCC in the literature varies between 0.3% and 4.8%. The variability depends on the timing of follow-up, with a higher incidence in prospective studies with strict follow-up. We advise ultrasound studies performed by specialized physicians every 6 months after transplantation. More detailed guidelines designed by the major international transplantation societies are necessary.