Rebamipide is a therapeutic agent for gastric ulcers and chronic gastritis. Hypobromous acid (HOBr) is generated not only by eosinophils but also by neutrophils in the presence of bromide ions in the plasma. At inflammation sites, rebamipide may encounter and react with HOBr to generated various products. When rebamipide was incubated with reagent HOBr in potassium phosphate buffer at pH 4.7 and 37°C for 4 h, several products were generated. A major product was identified as 3-bromorebamipide, a novel compound. Rebamipide does not react with hypochlorous acid (HOCl). However, when rebamipide was incubated with HOCl in the presence of NaBr, 3-bromorebamipide was generated in a dose-dependent manner, probably because of formation of HOBr. These results suggest that 3-bromorebamipide may generate from rebamipide at inflammation sites in humans.