During a 7 1/2 years period 31 patients representing 32 renal units presented with filling defects of the renal pelvis at excretory urography. All were treated with percutaneous resection of the pelvis. In 26 renal units there was histologic evidence of transitional cell tumor of varying grade and stage. With a follow-up from 4 to 79 months 8 recurrences including 1 case of tract tumor implant were seen. No other serious procedure related or later complications have appeared. The indications for using the percutaneous approach are discussed, and the results according to grade and tumor-stage are presented. Percutaneous resection of renal pelvic transitional tumors is recommended for low grade, non-invasive tumors, and for carefully selected patients with superficially invasive tumors.