The effect of esophageal distension on the lower esophageal sphincter (LES) in 14 normal volunteers and 6 esophageal achalasia (EA) patients was studied. A balloon-tipped catheter was introduced into the LES and a second one into the esophagus. The pressure response of LES to balloon distension of the esophagus and pharyngoesophageal sphincter (PES) was recorded. In normal subjects, esophageal distension caused significant decrease of LES pressure; this reflex action was reproducible and was called“esophagosphincter inhibitory reflex”(ESIR). PES distension caused insignificant LES pressure changes (p>. 05). Distension of the anesthetized esophagus or PES did not evoke LES pressure response. The ESIR was nonfatigable. In EA patients, the resting LES pressure was significantly higher than normal (p<. 01). Upon esophageal distension, the LES pressure increased, while no response occurred with PES distension. There was paradox ESIR in EA with a resulting esophagosphincter dyssynergia. To conclude, the ESIR seems to be of significance in esophageal motility disorders and may be incorporated as investigative tool in such conditions.