IBS is one of the most common of the gastrointestinal disease, but it can be a diagnostic challenge because of the many symptoms that overlap with other such diseases. Most common among the symptoms are abdominal pain, a feeling of intestinal distention or bloating, and either diarrhea or constipation. Patients may be found to have an exacerbation of symptoms with stress, and they may have an increased sensitivity to bowel distention. History and physical examination findings often can be relied on to make the diagnosis, avoiding overuse of laboratory testing. Treatment consists of patient education and support, lifestyle and dietary changes, and use of several pharmacologic agents for symptom relief. Antidepressants are being investigated as a possible additional form of treatment.