The reported normal values used in diagnosing and treating pediatric kidney stone formers are based on adult values or historic data from small studies. Urinary supersaturation indices which are now described in the adult stone literature as more sensitive predictors of stone composition, and precise predictors of response to therapy, are not established in children. The goals of this prospective study are to redefine normal values for pediatric urinary metabolites and supersaturation indices based on samples from a large number of healthy children and to identify if a difference in urinary supersaturations in children is protective.