Retroperitoneal fibrosis, a disease that can occur at any age, is characterized by a periaortic fibrous mass that often surrounds the ureters, leading to ureteral obstruction. Patients who present with this disease may complain of flank pain and acute renal failure. There is a high correlation with atherosclerotic disease of the aorta, although the pathogenesis of this disease remains unknown. Although recommendations for therapy remain empiric, prednisone seems to be efficacious in treatment; tamoxifen also may be effective. Retroperitoneal fibrosis usually does not lead to long-term morbidity or affect survival.