The case records of 72 patients attending a multidisciplinary spina bifida clinic were reviewed to discover the prevalence of renal parenchymal damage. 19.4% of the total population had such damage. More detailed analysis of the group according to age showed that the prevalence of parenchymal damage in the over ten year olds (27.3%), was twice that of the under five year olds (13.3%) but the same as the prevalence of "at risk" patients (26.6%) in this group. On the basis that most renal parenchymal damage occurs early we conclude that the current approach to investigation and treatment is reducing the incidence of renal parenchymal damage in this population. Further reduction would require the early identification of the high risk bladder before the onset of hydronephrosis.