In an effort to compare objectively the two most commonly employed methods of supravesical urinary diversion, the cutaneous ureterostomy and the ileal conduit, this study was designed to compare functionally each technique in the experimental animal. Sixteen female mongrel dogs underwent ligation of the distal right ureter. One week later, diversion of the right ureter was performed by either cutaneous ureterostomy or ileal conduit in two groups of animals. One month following diversion, the function of the diverted right kidney was compared to the control left kidney in all dogs and radiological evaluation was done. In the groups of dogs diverted by the ileal conduit, renal function studies were significantly better and radiologic interpretation revealed a more nearly normal collecting system. The data strongly support the position that the ileal conduit is the preferred route for urinary diversion in the dog. The clinical application is discussed.