It is increasingly evident that bidirectional communication betweenthe gastrointestinal microbiota and the brain occurs and plays arole in health and disease. Diseases as diverse as obesity, autism,and anxiety have been linked to the microbiota in preclinical models.Further, both human and animal studies have shown that modulationof the microbiota with probiotics or antibiotics can changeaspects of behavior or brain function. As humans age, there is adecrease in the diversity of the gut microbiota, and a decline inthe bacterial species often considered to be beneficial. It has beenhypothesized that this change may be associated with cognitivedecline, mood alterations, and neurological disease. In this presentation,I will review the scientific basis of microbiome-brain interactions,the preclinical and clinical data that support a role for themicrobiota in brain function, and the role of probiotics as potentialtherapeutic agents for healthy aging.