Specific Aims: 1) To develop a minimally-invasive assay that can accurately identify children with ASD/MD from the general ASD population. 2) To establish whether there is simply an ASD/MD subgroup or whether mitochondrial dysfunction occurs on a spectrum from mild to severe in ASD. 3) To determine the relationship between mitochondrial function and redox metabolism in children with ASD. 4) To evaluate the effect of mitochondrial dysfunction and glutathione redox status on language and social development and ASD symptoms.