The relation between peptic ulcer and stomach cancer has long been disputed, but there is accumulating evidence that gastric ulcer disease is positively associated and duodenal ulcerations negatively associated with the risk of developing stomach cancer. As Helicobacter pylori infection is associated with both types of ulceration and stomach cancer, the varying outcomes of the infection indicate that factors other than the infection must be of importance. At present, there is no convincing evidence that pharmacologic inhibition of acid secretion for treatment of peptic ulcer increases the risk of stomach cancer. However, some recent studies indicate that prolonged treatment with proton pump inhibitors may accelerate the development of atrophic gastritis, a risk factor for stomach cancer, in individuals infected with H. pylori. It has repeatedly been shown that there is an at least twofold increased risk of stomach cancer 15 years after gastric resection for peptic ulcer disease, and that the risk increases with the passage of time. Whether vagotomy has the same risk-increasing effect is still unclear.