Irritable bowel syndrome (IBS) is a gastrointestinal (digestive) problem that affects up to 15% of adults (during their lifetimes) in developed countries. Irritable bowel syndrome is a functional disorder, meaning that there is a problem with the functioning of the bowel rather than in the structure of the bowel, such as an obstruction or a tumor. Irritable bowel syndrome is completely different from Crohn disease or ulcerative colitis, which are inflammatory diseases of the intestine. Having IBS does not increase the risk of developing colon cancer. Gastroenterologists (doctors with specialized training in treating disorders of the bowel and other digestive organs) may be consulted to help diagnose and treat IBS. The February 22, 2006, issue of JAMA includes an article about irritable bowel syndrome. This Patient Page is based on one previously published in the August 18, 2004, issue of JAMA.