1. In this pilot study, the authors investigated the hypotheses there are increased concentrations of lactate in brain and plasma and reduced brain concentrations of N-acetyl-aspartate (NAA) in autistic children. 2. NAA and lactate levels in the frontal lobe, temporal lobe and the cerebellum of 9 autistic children were compared to 5 sibling controls using MRS. Plasma lactate levels were measured in 15 autistic children compared to 15 children with epilepsy. 3. Preliminary results show lower levels of NAA cerebellum in autistic children (p = 0.043). Lactate was detected in the frontal lobe in one autistic boy, but was not detected any of the other autistic subjects or siblings. 4. Plasma lactate levels were higher in the 15 autistic children compared to 15 children with epilepsy (p = 0.0003). 5. Higher plasma lactate in the autistic group is consistent with metabolic changes in some autistic children. The findings of altered brain NAA and lactate in autistic children suggest that MRS may be useful characterizing regional neurochemical and metabolic abnormalities in autistic children.