OBJECTIVE: Open surgical pyeloplasty has been the gold standard for the correction of ureteropelvic junction obstruction (UPJO). Endourological management of UPJO has gained increased acceptance, with reported success rates of 57-87%. It has been suggested that Acucise endopyelotomy (AE) should be the procedure of choice for patients with UPJO. The aim of this study was to assess the effectiveness of AE in the treatment of UPJO and the factors contributing to surgical outcome. MATERIALS AND METHODS: Forty-two patients (34 primary, 8 secondary UPJO) underwent AE between June 1995 and December 1999. Presenting symptoms were; pain 34 (80.9%), UTI 10 (23.8%) and haematuria 5 (11.9%). Preoperative evaluation included ultrasound and/or intravenous urogram with diuretic renography. Hydronephrosis was graded in 36 patients. Of these 4, 14, 9 and 9 had grade I, II, III and IV hydronephrosis, respectively. Twenty-four patients were stented prior to endopyelotomy and one required nephrostomy. Overall (true) success was defined as clinically pain free and radiologically no evidence of obstruction on diuretic scan. RESULTS: The average operating time was 45 min and mean hospital stay was 2.7 days. Mean follow-up was 27 months (range 6-55). The objective success rate was 52% and the subjective success rate was 64%. A total of 19 patients (45.2%) had long lasting clinical and radiographic treatment success. Three (7%) patients required nephrectomy and five (12%) underwent open pyeloplasty. Success rate for grade I/II hydronephrosis was 55.5% and only 27.7% with grade III/IV hydronephrosis. Normal renograms were found in 12 (48%) of those with perioperative extravasation compared to three (25%) without. Only one of the eight patients with secondary UPJO had a normal post-operative renogram. Size or type of stent used had no effect on surgical outcome. The substandard results were noted in patients with grade III/IV hydronephrosis, poor pre-operative renal function, secondary UPJO and without perioperative extravasation. CONCLUSIONS: Acucise endopyelotomy is a safe and minimally invasive procedure for the management of UPJO. Although the results of AE are suboptimal, its lower degree of invasiveness makes it reasonable choice for first-line treatment. Careful selection of patients will improve the results of AE, although multicentre randomized trials are needed to make a valued comparison with other techniques.