Twenty-seven patients with gastroesophageal reflux were prospectively investigated to define the role of duodenogastric reflux in the development of reflux esophagitis. Duodenogastric reflux was detected and quantified by pH monitoring of the gastric environment 5 cm distal to the distal esophageal sphincter. Alkaline duodenogastric reflux was identified by the occurrence of spontaneous, intense gastric alkalinization during fasting periods. Patients with reflux with esophagitis were distinguished from those without esophagitis by having fewer of these episodes and, consequently, more acid stomachs than had patients without esophagitis. As previously shown, refluxers with esophagitis also had more frequent acid gastroesophageal reflux and prolonged gastric emptying. These findings suggest that refluxers with esophagitis have a functional gastropyloric disturbance resulting in delayed gastric emptying, decreased frequency of alkaline duodenogastric reflux episodes, and more frequent acid gastroesophageal reflux than do refluxers without esophagitis.