Genetic disorders were identified infrequently among children presenting with Reye's syndrome in the past. During a two-year period, we evaluated four consecutive patients referred for intensive care of Reye's syndrome. A standard investigation for inborn errors of metabolism revealed that two patients had enzymatic defects of fatty acid oxidation, and the other two had partial deficiencies of ornithine transcarbamoylase. None had experienced a previous episode of Reye's syndrome, and three of the four had been entirely healthy in the past. Our experience suggests that as the incidence of Reye's syndrome has decreased, patients with its clinical features are now more likely to have manageable inborn errors of metabolism (e. g. disorders of ureagenesis, ketogenesis, and branched-chain amino acids).