A case of primary carcinoma in situ of the upper urinary tract in a 72-year-old woman is reported. The patient who complained of left lower abdominal pain was referred for a suspicion of left ureteral stone. An excretory pyelogram showed mild left ureteral stricuture at the level of L3, but a stone was not detected in the ureter at the same level. Cytology of voided urine was positive for malignant cells several times. Cystoscopic examination revealed no abnormality in the bladder. Retrograde left pyelogram demonstrated the ureteral stricture and no lesions either of stone or tumor in the ureter. However malignant cells were detected cytologically in the left ureteral catheteral urine. Left total nephroureterectomy with the bladder cuff was carried out under the preoperative diagnosis of carcinoma in situ of the upper urinary tract. Macroscopically, the wall of the ureter at the stenotic level had induration without apparent tumor mass. The pathological diagnosis was transitional cell carcinoma in situ from the renal pelvis to the mid-ureter. The primary carcinoma in situ of the upper urinary tract is rare. To our knowledge, this case is the 26th case reported in the Japanese literature.