We evaluated urodynamically 41 patients with posterior urethral valves because of signs or symptoms of incontinence (35), frequency (3), hydronephrosis (2) and infection (1). Findings included normal urodynamic evaluations in 3 patients, 2 had high voiding pressures secondary to outlet resistance and 1 had incontinence on the basis of external urethral sphincter damage. In the remainder 3 patterns of bladder dysfunction were identified. Myogenic failure with overflow incontinence occurred in 14 patients. In this group clean intermittent catheterization or Valsalva's voiding was used for emptying. Hyperreflexic bladders were seen in 10 patients. Pharmacological suppression of instability was effective in 5 of 7 patients treated; 1 required bladder augmentation. Eleven children had a small capacity bladder and poor compliance. Post-void residuals were low and these bladders were generally but not always stable. Pharmacological bladder relaxation was successful in 3 patients, 3 underwent augmentation, 1 did well with alpha-agonists and followup is unavailable on the other 4. These 3 patterns of bladder dysfunction represent an overlapping constellation of residual urodynamic abnormalities due to previous bladder outlet obstruction. Individual patients may show facets of several types of dysfunction associated with 1 predominant pattern.