The massively dilated ureter is a major therapeutic challenge that faces the pediatric urologist. In those instances when more conservative measures, such as control of infection or correction of the primary pathology, have failed or are likely to fail surgical treatment must be directed to the massively dilated ureter itself. The goals of reconstructive procedures are the elimination of residual urine, effective ureteral peristalsis, and efficient and/or urgent urinary drainage. We encountered these clinical settings in 244 children with 366 massively dilated ureters from 1965 through 1974. The underlying pathologic processes included primary megaureter, refluxing megaureter, posterior urethral valves, ureteral duplication with upper pole ectopic ureterocele or lower pole refluxing megaureter, simple ureterocele, ureterovesical junction obstruction, neurogenic vesical dysfunction, prune belly syndrome and acquired (iatrogenic) megaureter. The results of several reconstructive techniques are reviewed according to the excretory urogram, cystogram, renal function studies and the presence or absence of urinary infection. Analysis of the results with respect to the underlying pathologic entity responsible for the massively dilated ureter indicates that the etiology is a crucial factor in determining whether surgical treatment should be recommended and the type of surgical treatment that will most likely be successful.