[Quantitative analysis of urinary organic acid].

We showed the optimum conditions for analysis of urinary organic acids using solvent extraction and GC/MS by the stable isotope dilution technique. Examples of the diagnosis in a case of heterozygote of ornithine transcarbamylase deficiency and a case of multiple carboxylase deficiency were described. The accurate quantitative analysis of urinary organic acids with stable isotope dilution technique is necessary for routine examination conducted in clinical laboratories.