Irritable bowel syndrome (IBS) is a common and potentially disabling functional gastrointestinal disorder characterized by abdominal pain and altered bowel patterns. A significant amount of clinical and research data suggest the importance of the brain-gut interaction in IBS. This review examines the observed high prevalence of psychiatric disorders in patients with IBS. The published literature indicates that fewer than half of individuals with IBS seek treatment for it. Of those who do, 50% to 90% have psychiatric disorders, including panic disorder, generalized anxiety disorder, social phobia, posttraumatic stress disorder, and major depression, while those who do not seek treatment tend to be psychologically normal. Both physiologic and psychosocial variables appear to play important roles in the development and maintenance of IBS. Recent information suggests that the association of IBS and psychiatric disorders may be more fundamental than was previously believed. A brain-gut model for IBS is presented, and the role of traumatic stress and corticotropin-releasing factor as modulators of the brain-gut loop is discussed. Finally, the rationale for the use of psychotropic agents in the treatment of IBS with or without psychiatric symptoms is presented.