In three patients with completely duplicated ureters, one obstructed and one patent, good drainage was obtained by anastomosing the two ureters above the site of obstruction. The obstructed ureter was not removed. Pyelopyelostomy has been used for the treatment of urinary incontinence associated with ureteral ectopia, and for ectopia itself; and for reflux in only one of two duplicated ureters. This appears to be the first report of its application to the relief of obstruction in one of two duplicate ureters. The experience described appears to indicate that such obstruction can be relieved by this procedure, provided one of two completely duplicated ureters is patent distal to the point of anastomosis.