Objectives: Urolithiasis in children is recognized with an increasing frequency, while exact etiological factors remain to be determined. The aim of this study is to compare the metabolic risk factors and saturation of urine in pediatric and adult calcium oxalate (Ca-Ox) stone formers. Methods: A total of 33 pediatric (mean age: 6.8 +/- 3.1 years) and 120 adult patients (mean age: 39.7 +/- 5.7 years), with documented Ca-Ox urinary stone disease, underwent a comprehensive metabolic evaluation at our institution. Beside a broad serum analysis, concentrations of calcium, oxalate, magnesium, uric acid and citrate were measured in 24-hour collected urine. Saturation of urine was calculated by Marshall-Robertson's nomograms. Results: Hypocitraturia, observed in 60.6%, and hypomagnesuria, detected in 39.4%, but not hypercalciuria, were the most common metabolic risk factors in the pediatric group. In adults, hypercalciuria still represented one of the major metabolic risk factors, detected in 44.1%, although hypocitraturia, observed in 45.8%, was the most prevalent metabolic risk factor, as it was in the pediatric group. Pediatric cases had significantly (p < 0.05) higher prevalence of hypocitraturia, hypomagnesuria and supersaturated urine when compared to adults. Metabolic abnormalities could be detected in a high percentage (82%) of primary and recurrent pediatric Ca-Ox stone formers, but not in primary adult stone formers. Conclusions: Metabolic risk factors significantly differ in pediatric and adult Ca-Ox stone formers. Hypocitraturia and hypomagnesuria seem to play a major role in stone formation, and metabolic abnormalities can be detected in a significant percentage of both primary and recurrent pediatric stone formers. Thus, a comprehensive metabolic evaluation is of utmost importance for all children with Ca-Ox stones. Copyright (C) 2003 S. Karger AG, Basel.