Dr. Chauhan and colleagues at the IBR will investigate biochemical changes associated with autism, particularly as they relate to markers of oxidative stress. Oxidative stress is a process that occurs when the generation of free radicals in the cell during normal metabolic processes overwhelms the normal defense mechanisms and leads to damage or death of cells in tissues essential to normal function. Oxidative stress has been associated with neurodegenerative diseases and may be linked to an abnormal immune response. This project will examine blood of children affected with autism and their non-affected siblings to determine various markers of oxidative stress, the inflammatory response and the function of the immune system. In addition to diagnostic assessment, the symptom severity will be established to better understand the influence of the oxidative stress and immune responses in subgroups of children with autism spectrum disorders. What this means for people with autism: This study will allow the investigators to measure a wide array of markers associated with oxidative stress, thereby providing a better understanding of the mechanism by which oxidative stress may occur in individuals with autism. Isolation of a particular biomarker in a subgroup of children with autism will lead to better treatments and potentially improved diagnostic assessments.