We report the results of a prospective study conducted to identify neonates with myelomeningocele at risk for changes in the upper urinary tract. Thirty newborns underwent full urological evaluation and were followed for a mean period of 18.2 months. The initial studies included voiding cystourethrography, excretory urography and urodynamic tests. Followup consisted of periodic radiographic studies and repeat urodynamic testing if any changes were observed. According to urodynamic findings the patients were divided into 2 groups: group 1 consisted of 9 neonates (30 per cent) with detrusor-sphincter dyssynergia and high pressure, decreased-compliance bladders, and group 2 consisted of 21 children (70 per cent) with atonic bladders and low pressure, reduced-compliance bladders without dyssynergia. In group 1, 55 per cent of the patients had initially abnormal radiographic findings in contrast with 28.5 per cent in group 2. Anticholinergic drugs and clean intermittent catheterization or vesicostomy reversed the changes in 40 per cent of the children in group 1, 40 per cent remained stable and 20 per cent showed signs of deterioration. Four children in group 1 with normal neonatal radiographs were treated expectantly and at followup they all showed signs of deterioration. The neonates in group 2 with normal radiographic findings remained normal at followup. Of those who initially had changes 67 per cent reversed to normal without treatment, 17 per cent remained stable and 17 per cent had deterioration. Newborns with detrusor-sphincter dyssynergia or high pressure, reduced-compliance bladders are at high risk of having upper urinary tract changes and require preventive decompressive treatment. Children with atonic or low pressure, reduced-compliance bladders and those with a coordinated bladder and sphincter are at low risk and need only close followup.