Objective To determine the incidence of symptomatic and 'silent' obstruction after ureteroscopic procedures. Patients and methods In all, 1980 patients underwent ureteroscopy for ureteric calculi in two large centres. The methods of disintegration, auxiliary procedures used and type of stenting were considered. Intraoperative complications, in addition to the size and site of the stone, were assessed in relation to postoperative obstruction. The mean (range) follow-up was 42 (12-68) months, with patients assessed after 3-6 months and yearly thereafter. The postoperative evaluation included an assessment of pain, renal ultrasonography, a plain abdominal film, intravenous urography, and a diuretic renal scan in some cases to confirm obstruction. Results The success rate of stone removal was 98.5%. The failures were related to the size of the stone (>2 cm; P < 0.001). In eight patients there was a ureteric perforation, and six of these developed a ureteric stricture. A stricture also occurred in 12 patients (0.6%) during the follow-up; these included nine of 204 with stones of >2 cm (4.4%), compared to three (0.17%) of 1746 patients with stones of <2 cm (P < 0.001). Fourteen patients presented with pain (0.7%), and five had no obstruction, while in nine (0.46%) the pain was associated with obstruction. There was silent obstruction in three cases (0.15%). The negative and positive predictive values for pain were 99.8% and 64.3%, respectively. Conclusions Radiographic surveillance for stricture formation and obstruction is mandatory in patients who are symptomatic after ureteroscopy, and for up to 18 months in patients with intraoperative complications or with a stone of >2 cm in the proximal ureter.