Since we have started organic acid analysis on Jul. 1997, we have been collecting data about organic acidemias in Korea. The data presented here is our 3 years experience in organic acid analysis. We have collected 712 samples from major university hospitals all over the Korea, large enough for relatively accurate incidence of organic acid disorders. We are using solvent extraction method with ethylacetate, MSTFA for derivatization and quantitation of 83 organic acids simultaneously. Out of 712 patients sample, 498 patients sample (70%) showed no evidence of organic acid abnormalities. Out of 214 remaining samples we have found very diverse disorders such as methylmalonic aciduria(6), propionic aciduria (10), biotinidase deficiency (6), maple syrup urine disease (3), isovaleric aciduria (4), tyrosinemia type II (4), tyrosinemia type IV (1), glutaric aciduria type I (1), glutaric aciduria type II (22), 3-methylglutaconic aciduria type I (3), 3-methylglutaconic aciduria type III (7), HMG-CoA lyase deficiency (1), hyperglyceroluria (2), cytosolic 3-ketothiolase deficiency (55), mitochondrial 3-ketothiolase deficiency (3), 3-hydroxyisobutyric aciduria (2), L-2-hydroxyglutaric aciduria (2), fumaric aciduria (2), lactic aciduria with combined elevation of pyruvate (most likely PDHC deficiency) (28), lactic aciduria without combined elevation of pyruvate (most likely mitochondrial respiratory chain disorders) (35), SCAD deficiency (3), MCAD deficiency (1), 3-methylcrotonylglycineuria (1), orotic aciduria (most likely urea cycle disorders) (7) and 2-methylbranched chain acyl-CoA dehydrogenase deficiency (1). In conclusion, though the incidence of indivisual organic acidemia is low, the incidence of overall organic acidemia is relatively high in Korea. Most of the patients showed some signs of neurological dysfunction. In other words, organic acid analysis should be included in the diagnostic work up of all neurological dysfunctions.