Chronic (atrophic) gastritis is a progressive disease which in a small proportion of patients leads to severe (total) atrophy (severe grade of chronic gastritis) of the antral or body mucosa or both. Chronic gastritis is a premalignant condition which favours the development of gastric cancer. Chronic gastritis precedes gastric cancer and shows a severalfold increase in the risk of gastric cancer compared to subjects with histologically normal stomach. Several tentative modifications to the estimate of the risks may be presented: (i) a severe risk of developing gastric cancer is restricted to subjects with a severe grade of chronic gastritis (ii) the risk of gastric cancer is increased in subjects who have either severe antral or body chronic gastritis, the risk being approximately three to five times higher in the antral chronic gastritis (B-type of gastritis) than in the body chronic gastritis (A type of gastritis); (iii) the antral and body chronic gastritis are independent risk factors for gastric cancer, the joint risks being multiplicands of the marginal risks i.e., the estimated risk is highest in those subjects who show severe chronic gastritis in both the antrum and the body (AB type of gastritis); (iiii) the chronic gastritis mediated gastric cancer risk is limited to gastric cancers of the intestinal type, and thus covers only a proportion of all cases of gastric cancer. In the highest risk groups it may be estimated that the probability of a subject developing gastric cancer in subsequent decades is up to 30% if the subject is a young man who has severe chronic gastritis in his antrum, or who has it coexistently in the antrum and body.