To examine the efficacy of Lactobacillus gasseri OLL2716 (LG21) as a probiotic for Helicobacter pylori in humans, 31 subjects infected with the bacterium ingested yogurt containing LG21 daily for an 8 week period. The [(13)C]urea breath test and assays of serum pepsinogens revealed a significant improvement following LG21 treatment. LG21 was thus determined to be effective in both suppressing H. pylori and reducing gastric mucosal inflammation.