A new case of neonatal glutaric aciduria type II is reported. Neonatal acidosis, hypoglycemia, and hyperammonemia were characteristic. The baby died at four days of age. Organic acid analysis revealed massive glutaric aciduria with elevated concentrations of butyric, isobutyric, n-butyric, and isovaleric acid in his urine. The baby's pedigree suggested strongly an X-linked recessive mode of inheritance. Clinically, biochemically, and genetically glutaric aciduria type II is an heterogeneous disorder. The neonatal form is an X-linked inherited disorder which presents early in life, and is associated with metabolic acidosis, hypoglycemia, and hyperammonemia, and leads to death in the neonatal period. The mild form is an autosomal recessive inherited disease which may present even in adults, and is associated with recurrent hypoglycemia without ketosis and usually improves. Nevertheless the same unusual organic acid pattern is observed in both forms. The basic biochemical defect must be distinct and has not been elucidated.