Background. We sought to analyze the feasibility of prophylactic contralateral nephroureterectomy for renal transplant recipients with urothelial carcinomas. Methods. We analyzed the medical records of 12 renal transplant patients who underwent unilateral laparoscopic nephroureterectomy (first operation). Postoperative pathologic examinations confirmed that they all had urinary tract transitional cell carcinomas. At 1-3 months after the first operation, all patients underwent prophylactic contralateral nephroureterectomy (second operation). Results. Before the second operation, 2 patients were found to have hydronephrosis on computed tomography (CT), and postoperative pathologic examinations confirmed the lesions to be urothelial carcinomas. The other 10 patients had no detectable signs of urothelial tumors before the second operation, but postoperative pathologic examinations indicated that 3 had transitional cell carcinomas. All patients were followed for 4-70 months. Eleven patients survived; 1 died of heart attack unrelated to the procedures. Conclusions. The incidence of contralateral upper urinary tract urothelial carcinoma is high in renal transplant recipients with posttransplantation urinary tract malignancies. If there are no other health risks, prophylactic contralateral nephroureterectomy should be considered.