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Measurement of oxalate in urine is important for the diagnosis of primary hyperoxaluria (McKusick 259900) and the secondary forms produced by excessive intake or abnormal intestinal absorption of oxalate (1). Determination of glycolic acid is essential for the diagnosis of primary hyperoxaluria type 1. Finally, to estimate the risk of stone formation in calcium oxalate urolithiasis and nephrocalcinosis, simultaneous determination not only of calcium but also of citrate (a potent inhibitor of calcium oxalate and calcium phosphate crystallization) and other constituents (electrolytes, phosphate and sulfate) is required to calculate urinary calcium saturation (2). Ion-chromatography HPLC (3)(4) and specific enzymatic assays (5)(6) are available only in specialized laboratories. In addition, preservation and storage of liquid samples may influence the stability of oxalate and glycolate (7). Use of urinary filter spots is a practical alternative for the collection and safe transport of samples to be analyzed for many metabolic disorders. To evaluate the age-related changes of oxalate, glycolate, citrate, and sulfate in a pediatric population, we developed an automated ion-chromatography system for the simultaneous measurement of these anions in urine and established their reference values for liquid urine samples as well as for dried urine on filter paper. We studied 20 individuals from each age group ( 16 years), all without renal or metabolic disease, all on a routine food intake at the time of study. The urines were preserved with 6 mol/L HCl at pH 1–2 to prevent nonenzymatic conversion of ascorbate to oxalate. Filter paper strips (3 × 5 …