Ureteroscopy is an important technique in the management of calculous disease and ureteral lesions but it appears to have a greater potential for injury than percutaneous nephroscopy. In 2 years 4 patients with severe ureteroscopic injuries were treated. In 3 patients complete obstruction of the ureter occurred, and 1 had a major ureteral tear, prolonged urinary extravasation and infection. Even in the presence of total ureteral occlusion patients with short strictures were managed successfully percutaneously but the 2 patients with longer strictures were not. Previous surgery on the ureter or pelvic surgery and radiation therapy appear to be negative factors that affect adversely the ureteral blood supply, and potentiate poor healing and scarring. Nephrostomy tube drainage and ureteral stenting after ureteral dilation appear to be important steps in the percutaneous management of these patients.