Of 102 consecutive endoureteropyelotomy cases followed for 1 to 10 years (mean 5) late recurrence was observed in 13% and long-term success was achieved in 73%. Of 67 cases with an available preoperative angiogram a strong association was noted between the existence of a vessel crossing the ureteropelvic junction and high grade hydronephrosis, and final failure and/or recurrence: long-term success rate was 39% when both factors were present and it was 95% when neither factor was present. Therefore, we recommend that the presence of a vessel should be determined preoperatively since it significantly influences the outcome.