A fifty-six-year-old woman underwent transurethral ureterorenoscopy and cold cup biopsy for evaluation of a filling defect of the left renal pelvis. The pathology indicated a benign lesion, and percutaneous resection was done with the nephroresectoscope. However, the pathologic diagnosis of the resected tissue showed it to be transitional cell carcinoma, grade I. Consequently we performed a nephroureterectomy with excision of a cuff of bladder and the nephrostomy tract. Residual tumor was found in deep layer of the renal pelvis. The implication from this case in defining the indications for endourologic management of tumors is considered.