There is a bidirectional relation between the central nervous system and the digestive tract, i.e., the brain-gut axis. Numerous data argue for a dysfunction of the brain-gut axis in the pathophysiology of irritable bowel syndrome (IBS). Visceral hypersensitivity is a marker of IBS as well as of an abnormality of the brain-gut axis. This visceral hypersensitivity is peripheral and/or central in origin and may be the consequence of digestive inflammation or an anomaly of the nociceptive message treatment at the spinal and/or supraspinal level. Stress is involved in the genesis and maintenance of IBS. Disturbances of the autonomic nervous system are observed in IBS as a consequence of brain-gut axis dysfunction. The contribution of the neurosciences, in particular brain imaging techniques, has contributed to the better understanding of IBS physiopathology. The better knowledge of brain-gut axis dysfunction has therapeutic implications, either through drugs and/or cognitive and behavioral therapies.