Helicobacter pylori infection is intimately involved in stomach cancer development and recent epidemiological studies have indicated that the consumption of allium vegetables reduces the risk of gastric neoplasia. Therefore, in the present study, we investigated the effect of a garlic extract on H. pylori-induced gastritis in Mongolian gerbils. Garlic extract was fed to animals at doses of 1, 2 and 4% in the diet from 4 h after H. pylori inoculation until the end of the experiment, at week 6. With the administration of garlic extract, H. pylori-induced gastritis in animals was decreased in a dose-dependent manner, and significantly so at 4%. The numbers of hemorrhagic spots in the glandular stomach and the microscopic score for gastritis were significantly reduced from 19.2+/-15.6 and 5.9+/-0.8 in control gerbils to 8.1+/-11.2 and 4.2+/-1.5, respectively, by 4% garlic extract treatment. The stomach wet weight (1.04+/-0.22 g) of control gerbils was also reduced by 4% garlic extract (0.86+/-0.18 g). However, the number of viable H. pylori was not changed by the garlic extract treatment. The above observations indicated that garlic extract might be useful as an agent for prevention of H. pylori-induced gastritis, leading to reduction in the risk of gastric cancer.