Relationship between the recurrence of gastric ulcer and fundal gastritis was examined by the endoscopic Congo red test. On the basis of the extent of f undal gastritis, healed gastric ulcers were classified into two groups, i.e., 1) those with little or no fundal gastritis, and 2) those with moderate or severe f undal gastritis. In each group, rate of recurrence, location of recurrent ulcer and acid secretion were studied, and obtained the following results.1. Among a total of 84 cases, 32 (38.1 %) showed recurrence once or twice during the 1-year follow-up period. Among 33 cases with little or no fundal gastritis, only 18.2 % of them showed recurrence, but recurrence was more common in cases with moderate or severe f undal gastritis.2. Location of recurrent ulcer was almost identical with initial ulcer. However, there could be found a correlation between the location of recerrent ulcer and the extent of fundal gastritis. In general, location of recur rent ulcer was more proximal when f undal gastritis was. more extersive.3. An inverse correlation was observed between the rate of recurrnce and acid secretion. It seems likely that factors causing decrease in the mucosal defensive barrier are more important for the recurrence of ulcer than agressive factors, such as HCl.4. Gefarnate, which restores or potentiates the anatomical and functional unity of the mucous barrier, was effectiv-for the prevention of recurrence.Gastroenterological Endoscopy 18: 122-126, 1976.