Retroperitoneal fibrosis presents with a clinical and roentgenographic spectrum involving the ureters, inferior vena cava, iliac vein and rectum. The clinical and roentgenographic aspects of this spectrum are discussed and illustrated. The medial deviation of tapered obstructed ureters in the lower lumbar region is described as a "classic sign" of retroperitoneal fibrosis. A comparison statistical analysis of the position of the ureters relative to the lower lumbar spine and sacrum was done comparing 21 cases of retroperitoneal fibrosis with 60 normal cases. This analysis is shown and the lack of significant difference between the 2 groups is demonstrated.