We studied 53 neurologically normal children with recurrent urinary tract infection who were found to have bladder-sphincter incoordination characterized by voluntary sphincteric constriction during involuntary uninhibited bladder contraction. Increased intravesical pressure was documented during these events and was associated with vesicoureteral reflux in nearly 50 per cent of the children and with abnormalities of the ureteral orifice in 30 per cent of those without reflux. We hypothesize that increased intravesical pressure causes urinary infection in these children and produces a spectrum of intravesical anatomic distortion that predisposes to vesicoureteral reflux. In a prospective uncontrolled study treatment of the uninhibited bladder contractions allowed 58 per cent of the patients to maintain sterile urine without subsequent antimicrobial therapy after cure of the initial infection.