Irritable bowel syndrome (IBS) is an extremely common cause of consultation, and at present is diagnosed on the basis of symptoms and a few simple exclusion tests. Exclusion diets can be successful, but many patients have already attempted and failed such treatments before consulting. Anxiety and somatization may be an important driver of consultation. Patients' concerns should be understood and addressed. Those with prominent psychiatric disease may benefit from psychotherapy. Hypnotherapy benefits symptoms in those without psychologic disturbance, but its availability is limited. Antidepressants are effective in improving both mood and IBS symptoms globally, and the evidence is particularly good for tricyclic antidepressants. Although antispasmodics are currently the most commonly prescribed drugs, most responses (75%) are due to the placebo effect and not specific to the drug. Bulk laxatives such as ispaghula can increase stool frequency and help pain, but bloating may be aggravated. Loperamide is effective treatment for urgency and loose stools, but less effective for bloating and pain. 5-HT(3) antagonists such as alosetron improve urgency, stool consistency, and pain in diarrhea-predominant-IBS. The 5-HT(4) agonist tegaserod shows modest benefit in constipation-predominant IBS, improving stool frequency, consistency, and bloating as well as global improvement. There are many new drugs, such as cholecystokinin, neurokinin, and corticotropin receptor antagonists, in development.