We previously demonstrated that activated neutrophils increased the susceptibility of gastric mucosa to acid-induced injury in rats. As rebamipide, an anti-ulcer agent, inhibits neutrophil activation, we examined whether the rebamipide reduces stress-induced gastric mucosal injury by decreasing susceptibility to acid-induced gastric mucosal injury in rats. Increase in both gastric mucosal permeability and gastric microvascular permeability evaluated by (51)Cr-EDTA clearance and Evans blue leakage, respectively, at 6 hr after Water-Immersion Restraint Stress (WIR) were significantly lower in animals with leukocytopenia than those in controls. Pretreatment with neutrophil elastase (NE) inhibitors, an anti-P-selectin monoclonal antibody (MAb), and rebamipide significantly inhibited these increases at 6 hr after WIR. These treatments also inhibited decrease in gastric mucosal blood flow observed at 6 hr after WIR. Acid-induced exacerbation of gastric mucosal injury in rats at 6 hr after WIR was inhibited by NE inhibitors, anti-P-selectin MAb, and rebamipide. Rebamipide significantly inhibited WIR-induced increase in gastric MPO activity at 8 hr after WIR. Observations in the present study raised a possibility that rebamipide decreases the susceptibility of gastric mucosa to acid-induced injury by inhibiting neutrophil activation.