In the West, the incidence of esophageal adenocarcinoma, which is a long-term complication of damage by gastroesophageal reflux, has been rising over recent decades. Two main factors are likely to account for this increase. The first is the rising incidence of central obesity which promotes gastroesophageal reflux. The second is the falling incidence of H. pylori infection and associated atrophic gastritis which reduces the acidity and peptic activity of gastric juice, the main factors damaging to the esophageal mucosa. The rise in esophageal adenocarcinoma has been mirrored by a fall in gastric cancer consistent with H. pylori atrophic gastritis protecting from the former and predisposing to the latter. The incidence of gastric cancer in Japan is still above the level at which a rise in esophageal adenocarcinoma became apparent in the West. Esophageal adenocarcinoma is likely to rise in Japan also as the incidence of gastric cancer falls but the degree of rise will depend on a variety of other environmental and genetic factors.