At our clinic we followed 320 renal transplant recipients, 16 of whom developed malignancies within 15 yr. Ten of the 16 malignancies were transitional cell carcinoma (TCC) of the urinary tract. The modalities of treatment included standard nephroureterectomy with bladder cuff removal for upper tract tumor, transurethral resection for superficial bladder tumor and partial cystectomy for one case of invasive bladder tumor, as requested by the patient. Post-operative intravesical chemotherapy with epirubicin, or immunotherapy with bacillus Calmette-Guerin (BCG) were carried out for superficial bladder tumor. Cyclosporine (CsA) used as post-transplant immunosuppressant was switched to low dose azathioprine (Aza) at the initial diagnosis of TCC. Four patients experienced tumor recurrence despite conversion of immunosuppressant from CsA to Aza. Among these 10 patients, five maintained normal renal function, three returned to hemodialysis without tumor recurrence, and two patients died of cancer.