Irritable bowel syndrome (IBS) is a very common functional gastrointestinal disorder characterized by abdominal pain or discomfort with bowel habit changes. However, its pathogenesis and pathyphysiology have been poorly understood. There were many robust functional and anatomical evidences in Korea for visceral hypersensitivity, low-grade inflammation and immunologic alterations, brain-gut interaction and genetic factors in the development of IBS. The link between pathophysiologic changes and gastrointestinal symptoms would be the strong basis for the relevance of target therapy in this condition. The ROME III criteria represent the current gold standard for the identification of characteristic and supportive symptoms of IBS and for the categorization of IBS patients into symptom-based subgroups with exclusion of organic diseases. There were some limitations in use of Rome III criteria in the clinical practice and research fields. Test of Rome III are needed, especially in Korea.