The frequency of Helicobacter pylori was histopathologically evaluated in biopsy specimens of the gastric mucosa from 112 patients which endoscopically diagnosed as erosion. The specimens, histopathologically diagnosed as chronic gastritis, were divided into eight groups according to age, sex and location. The Helicobacter pylori infection was revealed in 65% of all specimens observed, and the frequency in patients of their sixties was lower than that of the forties. The frequency in the elder was the lowest in the transitional zone of the gastric mucosa. These findings indicate that the decrease in the frequency of Helicobacter pylori begins in the transitional zone and subsequently in the antrum.