Thirteen patients who received surgical treatment for histologically proven retroperitoneal fibrosis were reviewed retrospectively. All patients had idiopathic disease, bilateral in 11 patients. Elevated ESR occurred in 12 patients and in eight patients the hemoglobin value was decreased preoperatively. Intravenous urography on admission was normal in six kidneys, excretion was delayed in four kidneys and another four upper urinary tracts were dilated. No excretion was seen in four kidneys and eight kidneys were not examined urographically because of uremia. Ureteric obstruction was treated surgically by ureterolysis alone in two ureters, by ureterolysis and lateral displacement in eight ureters, by ureterolysis and intraperitonealization in 12 ureters and by ureterolysis and omental wrapping in two ureters. After primary surgery one nephrectomy was performed because of a nonfunctioning kidney. Postoperatively 19 kidneys are functioning well, in three the function is poor and there is no function in three kidneys. According to our experience the cornerstone of the surgical treatment is complete and extensive ureterolysis and permanent displacement of the ureter from the area of fibrosis.