Barostat is equipment for studying smooth muscle tone and sensory thresholds in the gastrointestinal (GI) tract. The principle of it is to maintain a constant pressure within an air-filled bag positioned in the lumen of the GI tract to be studied. Patients with irritable bowel syndrome (IBS) have been shown to have lower pain thresholds by barostat. Barostat would be one of the key procedures for studying pathophysiology in patients with IBS, although this method should be further standardized.