We review the complications and failures in our first 64 patients who underwent endopyelotomy. There were 2 intraoperative complications (3.1 per cent) necessitating an open operation. Postoperative complications included leakage around the stent or irritative bladder symptoms, which were treated by repositioning the stent, and 2 instances of ureterovesical stenosis, which have led us to stent the entire ureter in recent cases. There were 7 failures, 4 in patients who in retrospect were not suitable candidates for the percutaneous operation (long stenotic segment and redundant renal pelvis) and 3 for which there was no obvious cause. All failures were apparent soon after removal of the stent that was inserted at the end of the procedure.