The association between the topographic distribution of Helicobacter pylori colonization, inflammation and atrophy of the gastric mucosa, and fasting gastric pH was studied in a population with high prevalence of multifocal atrophic gastritis. Increasing atrophy of the antrum was associated with decreasing H pylori colonization of the antrum itself, but increasing colonization of the corpus. Advanced atrophy was associated with high fasting gastric pH. However, after therapeutic eradication of H pylori, inflammation subsided and gastric pH decreased indicating improved acid secretion despite persistent atrophy. The authors propose that antral atrophy fosters the colonization of oxyntic mucosa by H pylori, thus impairing acid secretion and causing hypochlorhydria that may further promote colonization of the oxyntic mucosa. Eradication of H pylori significantly improves hypochlorhydria. It may restore acid secretion in most patients, regardless of the presence of atrophy, which is an effect that may be of great benefit in halting the process of gastric carcinogenesis.