Autism is a developmental disorder characterized by disturbance in language, perception and socialization. A variety of biochemical, anatomical and neuroradiographical studies imply a disturbance of brain energy metabolism in autistic patients. The underlying etiology of a disturbed bioenergetic metabolism in autism is unknown. A likely etiological possibility may involve mitochondrial dysfunction with concomitant defects in neuronal oxidative phosphorylation within the central nervous system. This hypothesis is supported by a frequent association of lactic acidosis and carnitine deficiency in autistic patients. Mitochondria are vulnerable to a wide array of endogenous and exogenous factors which appear to be linked by excessive nitric oxide production. Strategies to augment mitochondrial function, either by decreasing production of endogenous toxic metabolites, reducing nitric oxide production, or stimulating mitochondrial enzyme activity may be beneficial in the treatment of autism.