Since 1982, 201 patients have undergone percutaneous incision for congenital or secondary obstruction of the pyeloureteral junction, and 171 of them have now been followed up for up to 63.3 months (12.5 +/- 11.5 months on average). All preoperative data, such as clinical and laboratory findings and results of i.v. urography and isotope nephrography, were usually controlled 6 months postoperatively. Depending on the degree of preoperative hydronephrosis, we found good and very good results in 78% of the patients followed up. Results were better in patients who had had primary stenoses, and younger patients had better outcomes than older ones. The treatment turned out during follow-up to be more successful for short stenoses than for longer ones. When pelvic or high ureteral stones were present the long-term results were less good. There were 16 patients with recurrences of obstruction, 15 of whom underwent another, this time successful, percutaneous pyeloplasty. Only 1 patient required open plastic surgery after three unsuccessful attempts at endoscopic surgery. We conclude that percutaneous pyeloplasty as we perform it is a safe endoscopic procedure that can produce reproducibly good long-term results comparable to those of open plastic surgery for primary pyeloureteral obstruction. In the case of secondary stenoses, however, a percutaneous approach should always be tried first, if in any way possible.