We report the case of a patient with 3-hydroxy-3-methylglutaric aciduria who presented with a repeat attack of Reye like syndrome clinically. Vomiting and somnolence, generalized tonic and clonic convulsions with hepatomegaly, hyperammonemia, liver function impairment, and mild metabolic acidosis were the presenting signs. 3-hydroxyisovaleric, 3-methylglutaric, 3-methylglutaconic and 3-hydroxy-3-methylglutaric acids were detected in the urine by gas chromatography-mass spectrometry. 3-methylglutarylcarnitine was also identified in the urine by fast atom bombardment and tandem mass spectrometry. Therefore, the possibility of metabolic disease should be considered in neonates and infants with repeat attacks of Reye like syndrome and a history of similarly affected siblings.