Irritable bowel syndrome (IBS) is a disorder that interferes with the normal functions of the large intestine (colon). It is characterized by a group of symptoms--crampy abdominal pain, bloating, constipation, and diarrhea. One in five Americans has IBS, making it one of the most common disorders diagnosed by doctors. It occurs more often in women than in men, and it usually begins around age 20. IBS causes a great deal of discomfort and distress, but it does not permanently harm the intestines and does not lead to intestinal bleeding or to any serious disease such as cancer. Most people can control their symptoms with diet, stress management, and medications prescribed by their physician. But for some people, IBS can be disabling. They may be unable to work, go to social events, or travel even short distances.