There are few pharmacological options to treat autism, and the currently available drugs target only specific symptoms, such as disruptive behavior. Several lines of evidence suggest the presence of high levels of oxidative stress in autism: reduced levels of glutathione, the brain’s predominant antioxidant; oxidative damage to lipids and other cellular components; and differences in antioxidant gene expression between people with autism and controls. In other neuropsychiatric disorders with similar patterns of oxidative stress, clinical trials on the use of the antioxidant N-acetyl cysteine (NAC), which boosts glutathione, have shown promising results. NAC also impacts the neurotransmitter glutamate, and changes in glutamate levels are also seen in autism. NAC has an excellent tolerability profile, and is a relatively natural treatment option that is currently available as a nutritional supplement. A pilot study of NAC treatment for autism has shown both a reduction in irritability and good tolerability of the compound. These promising results need to be replicated in a larger and more definitive study. Michael Berk and his team at Deakin University in Melbourne, Australia are conducting a randomized, placebo-controlled clinical trial of NAC with 80 children who have recently received a diagnosis of autism. They plan to administer a daily oral dose of NAC for six months, in order to test the efficacy and tolerability of NAC in treating core symptoms of the disorder. If NAC proves to be superior to the placebo in improving autism symptoms, this could have a significant effect on the treatment of autism. This research project may also provide new insights into the pathophysiology of autism and targets for future drug development.