We report three patients with glutaric aciduria type I. The biochemical diagnosis of two cases was revealed by determination of free glutaric acid in urine, by using the CG/EM method. In the third patient, however, these levels were only slightly increased and the diagnosis was attained by the determination of total glutaric acid and glutaryl-carnitine. Serum carnitine levels were decreased in two cases. Clinical symptoms of this type of organic acidemia are highlighted by an acute or subacute presentation with signs of dysfunction of the neostriatum, simulating a cerebral paralysis with extrapyramidal signs. Homozygous patients have been reported with the same biochemical and enzymatic activity findings, but these patients were neurologically asymptomatic throughout life. Other features suggestive of the disease are macrocephaly associated with a widening of the subarachnoid spaces. Riboflavin and carnitine administration to these patients seems to prevent new bouts of neurological dysfunction.