Urinary incontinence following Posterior Urethral Valves (PUV) ablation has been attributed in the past to sphincter injury, but it is nowadays accepted that bladder dysfunction (BD) plays a determinant role. In order to assess BD evolution, we have evaluated, from 1982 to 1994, 48 boys with PUV by urodynamics (UD) studies. Age of the patients ranged from 10 months to 15 years. A total of 65 examinations were performed. We considered four groups: 0-3 years; 4-7 years; 8-12 years and > 12 years. Uninhibited detrusor contractions (instability), end filling pressure (EFP), bladder capacity and voiding detrusor pressure were evaluated in order to assess the presence of BD distinguishing it in: hypercontractility, hypocontractility and low-compliant bladder. The results collected confirm a high percentage of BD in PUV boys (71%) and the evolution of hypercontractility versus hypocontractility in 60% of patients considered.