A case with two separate transitional cell carcinomas of the bladder is reported in which neither tumor was evident on cystoscopy six months prior to resection. Transplantation of the ureters into an ileal loop, performed for chronic cystitis of long duration, did not prevent development of the tumors. Extensive atypical epithelial hyperplasia and areas of carcinoma in situ were noted in the giant tissue sections prepared from the cystectomy specimen. These changes were not evident in biopsy specimens taken from the bladder six months before the cystectomy, although a segment of distal ureter had had atypical epithelial hyperplasia five months before tumor was clinically evident in the bladder.