The delivery of drugs in the local gastric region has been studied for antimicrobial agents against Helicobacter pylori. The materials used in almost all related studies have been gastric biopsy specimens or gastric juice (9–11), and few investigations have focused on the concentrations of drugs in the gastric mucus (17). It has been reported that Helicobacter pylori inhabits the gastric mucus similar to the surface of the gastric mucosa (18–20). Furthermore, Shimizu et al have reported that Helicobacter pylori has a tendency to survive in the gastric mucus compared with the surface of the gastric mucosa in unsuccessful antimicrobial treatment (21). Therefore, we should examine the concentrations of antimicrobial agents not only in gastric biopsy specimens and gastric juice but also in the gastric mucus when we investigate the delivery of drugs against Helicobacter pylori. Although rebamipide has no direct antibacterial effect on Helicobacter pylori, Kato et al and Nebiki et al have reported that rebamipide has an additive effect on the rate of cureof Helicobacter pylori infection obtained with dual therapy with a proton pump inhibitor and amoxicillin (22, 23). The mechanism by which rebamipide increases the cure rate for dual therapy is unclear; however, an inhibitory effect of this drug on Helicobacter pylori adhesion to the gastric mucosa may indirectly interfere with the colonization of Helicobacter pylori (24). In this study, the COR and its change after ingestion of rebamipide in the gastric mucus was similar to that in the gastric mucosa. These results suggest that the delivery of rebamipide is by means of direct local penetration from the inside of the stomach to the gastric mucosa In conclusion, the COR in the gastric mucosa and gastric mucus exceeds the density that is needed to achieve rebamipide’s various antiulcer actions after its oral ingestion at an ordinary clinical dose. We assume that the rebamipide levels present in the gastric mucosa and gastric mucus are a result of local penetration