A series of 46 children treated by the author since January 1972 for congenital posterior urethral valves is presented: 22% were diagnosed at birth, 28% as neonates and 52% in the first 3 months of life. Ninety-three per cent had unilateral or bilateral dilatation of the upper urinary tract at the time the valves were diagnosed and 72% had ureteric reflux. Unilateral reflux occurred into the left ureter twice as often as the right. Renal failure was present at the time of diagnosis in 72% of all of the children but in 83% of those aged less than 3 months. Surface urinary diversion was used minimally during post-operative management and contributed little to the recovery of renal function. Reflux disappeared spontaneously in one-third of the refluxing ureters. Ureteric dilatation subsided spontaneously in 57% of dilated ureters. Surgery was performed mostly for reflux. Non-refluxing ureteric dilatation was made worse by surgery in a few instances and in others the dilatation improved with time rather than as a result of surgery. Renal function returned to normal in over 60% of the children who were in renal failure at diagnosis. Measurement of glomerular filtration rate was the most accurate method of predicting recovery of renal function: a value of less than 50% of normal for age at the time of diagnosis forecast persistent chronic renal failure with all its attendant complications.