Background: Swallow and esophageal distension-induced relaxations of the lower esophageal sphincter (LES) are associated with an orad movement of the LES because of a concurrent esophageal longitudinal muscle contraction. We hypothesized that the esophageal longitudinal muscle contraction induces a cranially directed mechanical stretch on the LES and therefore studied the effects of a mechanical stretch on the LES pressure. Methods: In adult opossums, a silicon tube was placed via mouth into the esophagus and laparotomy was performed. Two needles with silk sutures were passed, 90 degrees apart, through the esophageal walls and silicon tube, 2 cm above the LES. Tube was withdrawn and one end of each of the 4 sutures was anchored to the esophageal wall and the other end exited through the mouth to exert graded cranially directed stretch on the LES using pulley and weights. Results: A cranially directed stretch caused LES relaxation and with the cessation of stretch there was recovery of the LES pressure. The degree and duration of LES relaxation increased with the weight and the duration of stretch respectively. The mean LES relaxation in all animals was 77.7±4.7%. The required weight to induce maximal LES relaxation differed in animals (714±348g). The L-NNA, a nitric oxide inhibitor blocked the axial stretch induced LES relaxation, almost completely (from 78% to 19%). Conclusions: Our data support the presence of an axial stretch activated inhibitory mechanism in the LES. The role of axial stretch in the LES relaxation induced by swallow and esophageal distension requires further investigation.