An international working team defined the irritable bowel syndrome as distinct from other functional bowel disorders. Symptom criteria for the irritable bowel syndrome are known as the Rome criteria. Since there is no pathophysiological marker for any of these syndromes we must rely on symptoms for their definition and classification. The Rome nosology is a step towards better understanding of functional gastrointestinal disorders because the disparate syndromes are likely to have different causes and treatments.