The diagnosis and management of 12 patients with spontaneous non-traumatic urinary extravasation are described. It is important to distinguish extravasation of the fornical backflow type from that owing to frank rupture of the diseased renal pelvis. Most cases of the former variety are caused by calculous ureteral obstruction and can be managed conservatively. Surgical intervention is indicated for the latter variety (frank rupture) and is based on the requirements imposed by the patient's clinical condition, the persistence of obstruction or extravasation, or the presence of complications of extravasation such as urinoma or abscess.