AbstractDuodenogastric reflux has been implicated in the pathogenesis of complicated Barrett's esophagus and gastric ulceration. A group of 123 Barrett's patients were followed for a mean of 41 months; 9 (7%) developed gastric ulceration (GU). Of the Barrett's patients treated by antireflux surgery, 14% developed GU. We reviewed the gastric histology on 54 Barrett's patients (34 men, 20 women; average age 64 years) at presentation and classified the gastritis according to the Sydney system. A normal histologic pattern was present in seven patients; 15 patients had chronic pangastritis, 9 chronic antral gastritis, and 18 chronic gastritis of the corpus. Five patients had acute gastritis only, and in 74% there was reactive chronic gastritis. Of the patients with chronic gastritis, 45% (19 of 42) had histologic evidence of duodenogastric reflux, established by the bile reflux index. The presence of reactive chronic gastritis in Barrett's patients may have important pathophysiologic and therapeutic implications.