Intravenous pyelograms were obtained before and after operation in 82 patients who underwent conventional ureteroileocutaneous anastomosis and who were followed up for periods ranging from 6 to 66 months. Comparison revealed 2 important findings. Patients with normal or near normal pyelograms generally continued to show normal pyelograms. In contrast, patients with moderate to severe hydroureteronephrosis failed to improve or showed progressive dilatation. In this latter group, mostly children, in 10 instances the authors have excised the abnormal ureter and performed pyeloileocutaneous anastomosis. In every instance this has resulted in arrest or improvement of the hydroureteronephrosis.