We performed percutaneous perfusion of the upper urinary tract with Bacillus Calmette-Guerin (BCG) in 3 patients. Two of them had undergone unilateral nephrectoureterectomy for ureter carcinoma in situ and one had undergone radical cystectomy with bilateral ureterocutaneostomy for invasive bladder carcinoma. However, they suffered recurrent upper urinary tract carcinoma in situ within 2 years after their operation. Under ultrasound control a percutaneous nephrostomy tube was placed in the patient. Before BCG perfusion unobstructed flow from the renal pelvis to the bladder was confirmed and pyelovenous or pyelolymphatic back flow was excluded under fluoroscopy. A dose of 240 mg BCG was dissolved in 150 ml 0.9% saline. The flask was placed 20 cm above the kidney of the resting patient. A continuous flow of approximately 1 ml per minute was maintained. The perfusion was stopped after 2 hours and the nephrostomy tube was closed. Therapy was repeated at weekly intervals for a total of 6 perfusions (1 treatment course). In each of them urine cytology results became negative after 1 treatment course. No severe side effects were observed. Further investigation is also needed to determine whether BCG perfusion of the upper urinary tract could become a conservative treatment for carcinoma in situ of the upper urinary tract.