This study investigated the mechanism of gastroesophageal reflux (GER) in 10 healthy, asymptomatic subjects. Continuous recordings of esophageal pH and pressure were obtained over two consecutive nights from 6:00 p.m. to 6:30 a.m. The results showed that basal lower esophageal sphincter (LES) pressure varied widely among subjects and was not related to GER. Instead, GER occurred during transient episodes of inappropriate complete LES relaxation, which were often spontaneous or followed by appropriate sphincter relaxation induced by swallowing. Most GER episodes occurred within the first 3 hours after eating. During the night, LES relaxation and GER occurred only during transient arousals from sleep or when subjects were fully awake, but not during stable sleep. Esophageal clearance of refluxed acid was primarily achieved through primary peristalsis, with secondary peristalsis being less effective. The study concluded that GER in asymptomatic recumbent subjects is related to transient inappropriate LES relaxations rather than low steady-state basal LES pressure, and that primary peristalsis is the major mechanism for clearing the esophagus of refluxed material.This study investigated the mechanism of gastroesophageal reflux (GER) in 10 healthy, asymptomatic subjects. Continuous recordings of esophageal pH and pressure were obtained over two consecutive nights from 6:00 p.m. to 6:30 a.m. The results showed that basal lower esophageal sphincter (LES) pressure varied widely among subjects and was not related to GER. Instead, GER occurred during transient episodes of inappropriate complete LES relaxation, which were often spontaneous or followed by appropriate sphincter relaxation induced by swallowing. Most GER episodes occurred within the first 3 hours after eating. During the night, LES relaxation and GER occurred only during transient arousals from sleep or when subjects were fully awake, but not during stable sleep. Esophageal clearance of refluxed acid was primarily achieved through primary peristalsis, with secondary peristalsis being less effective. The study concluded that GER in asymptomatic recumbent subjects is related to transient inappropriate LES relaxations rather than low steady-state basal LES pressure, and that primary peristalsis is the major mechanism for clearing the esophagus of refluxed material.