Irritable bowel syndrome (IBS) is a common condition varying in severity from trivial to incapacitating. The more severe cases are associated with poor quality of life, absenteeism from work, frequent consultation with medical professionals, and psychosocial distress. Historically the disorder was often considered as purely psychosomatic in origin, but we now know that this is a gross oversimplification. Gastrointestinal disorders are better understood using the biopsychosocial model, which emphasizes the importance of biologic and psychosocial factors. This article reviews the epidemiologic association of IBS with psychological and social stresses and explores how such stresses may influence consulting behavior and outcome. This review also describes physiologic mechanisms that may be involved in IBS and discusses the role of psychological therapies and psychotropic medication in the treatment of this condition.