Immunosuppressive therapy increases the incidence of cancer after transplantation; however, immunosuppression is not an independent risk factor for transplantation secondary to renal cell carcinoma. Several mechanisms have been postulated to be responsible for the transformation of donor-derived cells to malignancy. These include viral or oncogene transfection from the subject to the donor cells, which is subsequently enhanced by altered immune surveillance, chronic antigenic stimulation of the donor, and cellular aging of the donor. Renal cell carcinoma is the most reported malignancy after renal transplantation. Although the vast majority of post-transplant malignancies involve non-urinary organs, renal cell carcinoma of the native kidney accounts for 5-15% of all tumors, while renal cell carcinoma of the transplanted kidney accounts for only 0.5-1.5%. For transplant recipients, the greatest risk factor for renal cell carcinoma is acquired cystic kidney disease. Continuous pre-transplant dialysis increases the risk of developing post-transplant renal cell carcinoma. Therefore, many centers perform regular ultrasound examinations of the native and transplanted kidneys. Many post-transplant tumors in allogeneic kidneys are found incidentally and are more common in deceased patients than in living patients. When diagnosed, renal transplant malignancies tend to be small (less than 4 cm) and have a low grade of biopsy characterization. While most renal cell carcinomas of the native kidney are clear cell carcinomas, most renal cell carcinomas of the transplanted kidney are papillary renal carcinomas. The risk of tumor recurrence or metastasis is very low after extensive tumor resection in transplant recipients. In a series of large-scale reports of transplanted kidney tumors, no one has died of cancer. Utilizing organs from donors with a history of known malignancies or from patients with active low-grade malignancies would increase the organ donation pool. Treatment of allograft kidney tumors used to be transplant nephrectomy because a poorer prognosis could be expected in immunosuppressed patients. However, it is now believed that immunosuppression does not accelerate in situ progression, metastasis, or transplanted kidney tumors. In fact, the risk of death due to renal dysfunction has outweighed the risk of the tumor itself, and allogeneic nephrectomy, termination of immunosuppression, and initiation of dialysis are only considered when the tumor is too large to preserve the kidney, or for other metastatic renal cell carcinoma in the graft. Cryoablation or radiofrequency ablation therapy is also recommended as a less invasive treatment option.