A case of mucinous adenocarcinoma of the renal pelvis occurring in association with urolithiasis (staghorn stone, upper third ureteral stone) and obstructive uropathy is reported. The kidney contained 2800 ml of jelly-lkie material. A series of careful surveys of the abdominal viscera failed to find any other primary lesion, and the patient is still doing well 1 year after operation. (J Urol R.O.C., 9:196-199,1998)