Esophageal peristalsis and lower esophageal sphincter(LES) function have an influence on gastroesophageal reflux disease(GERD). Incomplete contraction during primary and secondary peristalsis leads to poor clearance of refluxed gastric acid. Failure of LES function can result in a low basal LES pressure, absent or incomplete LES relaxation after swallowing, or an inadequate increase of LES pressure accompanying gastric activity. In addition, transient LES relaxation(TLESR) has been suggested as an important factor in GERD. Recent studies have indicated that TLESR has a relationship to nitric oxide(NO) and cholecystokinin(CCK).