The GC-MS method was successfully applied for the analy-sis of organic acids in urine samples obtained from hospitalizedchildren. Table 1 indicates that the creatinine-corrected excre-tion rates of all organic acids measured in the children’s urinesamples were within normal intervals. Analysis exhibited goodrepeatability (RSD < 9.8%). Fig. 2 shows a typical GC-MS chro-matogram from the analysis of organic acids in a child’s urinesample