The rate of certain malignancies in renal transplant recipients is 14 to 500 times higher than the rate in the general population. The reported prevalence rates for malignant tumors in various kidney recipient series range from 4% to 18% with an average of 6%. The tumors occur in patients who are younger than individuals affected in the general population, and the incidence rates rise with each year after transplantation. Since 1975, we have recorded 52 cases of malignancy development in 50 (3.7%) patients who were treated with P + AZA, P + CsA + AZA, or P + CsA + MMF therapy (P, prednisolone; AZA, azathioprine; CsA, cyclosporin A; MMF, mycophenolate mofetil). In this article, 50 renal transplant recipients who developed malignancy and were followed by the Transplantation Center at Başkent University Faculty of Medicine were analyzed. Analysis revealed that patients who received CsA had a higher incidence of Kaposi's sarcoma than those who received the standard regimen. Regarding other tumor types, our results showed no statistical differences among the incidence rates in the different treatment groups.