Autistic spectrum disorders are a diverse group of complex, persistent and pervasive neurodevelopmental conditions which are characterized by impairments in social communication, social interaction, often restrictive and repetitive patterns of behaviour, interests or activities. Probiotics have been shown to influence microbiota composition, therefore may be a useful novel therapeutic tool to restore normal gut microbiota, reduce inflammation and ameliorate behavioral symptoms associated with autistic spectrum disorders. Once the gut becomes leaky it is therefore possible to increase intestinal permeability which may allow the passage of bacteria, toxins and other metabolites which may lead to immune activation. For many years theories have been developed which implicate the possible role of immune dysfunction in autistic spectrum disorder. Administration of probiotics has been known to influence neuronal functioning, and attenuate pro-inflammatory immune responses. Pro-inflammatory immune response has been attenuated by the administration of Bifidobacteria.