The discovery of Helicobacter pylori opened a new field for extensive research on the interactions of this bacterium with the gastric mucosa in the past decades. Basic principles of infection, virulence factors, and treatment options have been identified and recognized. New questions have emerged concerning possible interactions of H. pylori with other bacteria in the human stomach. Herein we discuss hallmark findings in relation to H. pylori infection and the new evidence on other bacteria in the human stomach. Probiotic bacteria seem to interfere with colonizing H. pylori bacteria and thus influence the inflammatory response of the gastric mucosa to H. pylori infection.