A total of 29 patients received an ileal segment interposition between the upper and lower urinary tract for partial or total ureteral substitution, or for ileal wrapping around a massively dilated, aperistaltic ureter. Indications for an operation included the presence of an extensively diseased or short ureter and an aperistaltic megaureter that had failed previous reconstructive attempts. Nine patients (group 1) underwent an ileal sleeve procedure in an attempt to increase the ureteral peristaltic activity and facilitate drainage. Among these patients 7 (78%) had a stable upper tract radiologically and normal serum creatinine (less than 1.6 mg./100 ml.), while 2 (22%) had deterioration of the renal function. Ten patients (group 2) had undergone a myriad of reconstructions that failed and then underwent complete ureteral substitution with ileum. Among them, renal function (as evidenced by excretory urography and serum creatinine) is stable in 7 (70%) and deteriorated in 3 (30%). In 10 patients (group 3) the ureters were partially replaced by ileum in addition to a bladder augmentation procedure. Of these patients 8 (80%) have stable renal function and 2 (20%) had renal failure. Over-all, 7 patients have different degrees of renal failure; among them 2 (6.9%) are on dialysis and 2 (6.9%) have received a transplanted kidney. In groups 2 and 3 the results with an antireflux operation indicated that among 6 ureteroileal reimplantations 5 (83%) were successful, among 12 intravesical intestinal nipples 6 (50%) failed to prevent reflux and there was no case of obstruction, while among 4 ileocecal intussusceptions 2 (50%) were successful and 2 failed. Mucous secretion produced temporary ureteral obstruction in 1 ureter (3.4%), which resolved without surgical intervention. Some of the aforementioned procedures were done in the past and in some situations a different reconstructive technique would be considered presently. The surgical complexity and magnitude of the procedures justify their performance only in difficult clinical situations as an alternative to urinary diversion or renal autotransplantation.