Necrotic cystitis, also called incrustation cystitis, raises etiopathological and therapeutical problems, with relapse of the necrosis after removal of pathological tissue. Between 01.01.1999 and 31.12.2005 there have been 55 patients institutionalized in our Clinic, presenting lower urinary tract symptoms (LUTS). Instrumental investigations have demonstrated the thickening of the bladder wall, more frequently in the trigonum area. Ultrasound examination and cystography couldn’t exclude an infiltrative bladder tumor. Cystoscopy which showed necrotic bladder tissue, with calcareous incrustations, followed by the resection of the pathologic tissue. In 45 cases the histopathological result was necrotic cystitis and in 10 cases infiltrative urothelial bladder tumor or epidermoid metaplasia. In order to clarify the etiology of the necrosis an investigation protocol have been used, consisting of laboratory tests for autoimmune diseases, vascular or local causes that initiate the necrosis (previous surgery in the area, endoscopic interventions). In 5 cases with autoimmune disease, the treatment was transurethral resection and plasmapheresis. The evolution was favorable in 4 cases. Failure: 1 patient. In 12 cases the cause of the necrosis appears to be a diabetic vasculitis, judging by the deep necrosis, dispersed over several small areas. The posttherapeutic evolution depends on the correct treatment of diabetes. In 10 patients with previous endoscopic surgery, the necrosis has been induced by inadequate electrical currents or mechanical lesions. In 18 patients the causing factor remained unknown. The limited necrosis of the bladder can be caused by autoimmune diseases, vascular diseases (diabetes) and endo-urethral maneuvers. The endoscopic resection of the necrotic bladder wall to the healthy, well vascularised tissue beneath is an important therapeutic procedure. The treatment of the causing factors (autoimmune, vascular) will consolidate the healing. Not knowing the other causes will lead to failure, and repeated endoscopic treatment will result in short term ameliorations.