The relationship between chronic gastritis and peptic ulcer was studied in 97 patients, 51 with duodenal ulcer [DU] and 46 with gastric ulcer [GU]. Six biopsies (3 from the antrum and 3 from the body) were obtained under direct vision by means of an Olympus panendoscope. Chronic gastritis was classified according to the grade of inflammation (slight or moderate and intense) and its location (antritis or pangastritis). In gastric ulcer the relationship between frequency of chronic gastritis and the site of the ulcer (antrapyloric, at the angulus, body of the stomach) was established. Antritis was just as frequently observed in DU (94%) as in gastric patients (96%), but severe inflammation of the antrum was higher in GU (43%) than in DU (17%). Chronic gastritis of the gastric body was always accompanied by antritis in GU and DU, and was observed in 63% of the former group and 37% of the latter. Severe inflammation of the glandular portion of the stomach occurred in only 1 patient with DU (2%) and 7 with GU (15%). No relationship between the site of gastric ulcer and the frequency of chronic gastritis was observed.