In this retrospective study we evaluated incidence of malignancies observed among 718 renal transplant recipients with at least 6 months of follow-up. A total of 461 men and 257 women (mean age at transplantation 36.3 +/- 8.3 years) were included. Thirty three out of 718 recipients (4.6%) developed malignant neoplasia: 45.4% of these were Kaposi's sarcomas, 12.1%--cancers of the uterine cervix, 12.1% cancers of the stomach, 12.1%--basal cell carcinomas, 6.06%--posttransplant lymphoproliferative disorder. There was no significant effect of either cyclosporin A doses or OKT3/ATG on the incidence of the tumors. Mean age of transplant recipients with malignancies was statistically higher as compared to those without malignancies (45.5 +/- 8.2 years versus 36.1 +/- 8.4 years, p < 0.00001). The median time from onset of end-stage renal failure (dialysis start) and from the transplantation to the diagnosis of the tumor make up 32 (16-161) and 23 (5-158) months, respectively. One renal transplant patient suffered from multiple myeloma with aggressive course.