The experiences gained in the treatment of four patients with cystic pyeloureteritis are reported, stressing the significance of chronic inflammation in the development of the disease. Diagnostic and differential diagnostic problems are discussed with the conclusion that definitive recovery can be achieved only by radical surgical intervention. Beside this radical solution, the indications of conservative or palliative surgery are discussed. In conservative drug treatment the aimed application of antibiotics and administration of cortisone and vitamins are of great importance.