PURPOSE: For the accurate diagnosis of organic acidopathies, quantification of urinary organic acid should be done and we should know the normal ranges of each organic acid excreted in the urine. The amount of organic acids excreted in the urine shows wide variability according to ethnic group, diet and age. We have quantified 82 organic acids to make a Korean reference value. METHODS: Organic acid concentrations were quantified with gas chromatography and the individual acids identified with mass spectrometry in urine specimens from members of the healthy Korean population of ages of one day to more than 12 years, subdivided into four age groups : neonatal period(-2 mon), infantile period(-2 year), childhood period(-12 year) and adolescent and adulthood(over 12 years). For isolation of organic acids from urine, we used solvent extraction method with ethylacetate. Derivatization was done with MSTFA(N-methyl-N-trimethylsilylfluoroacetamide). The library and four points quantification curve for the quantification of each organic acid that we used have been developed by Dr. Giudici of Kayser Permanante Metabolic Laboratory, CA., USA. RESULTS: Quantitative ranges and frequency distribution patterns of urinary organic acid excretion are reported, as a basis on which to compare results obtained for patients whose clinical condition suggests that their excretion values may be abnormal. CONCLUSION: The quantitative values we observed, enable the relative significance of different urinary metabolites to be assessed.