The true incidence of posterior urethral valves is unknown. They may cause major or minor urinary tract malfunction, reflecting the broad spectrum of degree of congenital malformation. Of 124 boys with posterior urethral valves 76 per cent had only minor secondary abnormalities and 24 per cent had secondary problems, such as large paraureteral diverticula, high grade reflux with upper tract damage, megaureter, hydronephrosis and uremia. The diagnosis of posterior urethral valves was based on voiding cystourethrography and endoscopy. Only types I and III values were found in our study. Except for 1 case, the valves were fulgurated endoscopically. Upper tract drainage was necessary in only 4 cases and kidney transplantation was required in 1. Most patients were cured by valve fulguration. Reflux disappeared in more than 50 per cent. Urodynamic studies in 16 patients with persistent complaints of diurnal and nocturnal enuresis revealed further bladder dysfunction.