Two ureteral sheaths and the vesical musculature combine to form a watertight ureterovesical junction but the precise anatomy and function of each component are still somewhat contentious. The morphology was studied in postmortem specimens of children with and without paraureteral diverticula and urethral obstruction, and function by deductive reasoning from radiographic and surgical observations in living children. Waldeyer's fascia (the superficial sheath) of the ureter was found to seal the potential space between the tunnel wall and the ureter, and deficiencies were associated with hiatal hernias. The deep sheath provided anchorage of the ureter to the trigone and through the attachments of the superficial sheath to the bladder wall. Both sheaths and the tunnel muscles could be identified clearly and dissected precisely at operations involving the ureterovesical junction to facilitate the surgical procedures.