In the review risk factors which transformations chronic atrophic a gastritis in a stomach cancer promote are analyzed. The characteristic of precancer conditions as increase in risk of development of a cancer of a stomach is given. As risk factor of a cancer of a stomach definition of subtypes intestinal metaplasia is offered, dividing on full and incomplete taking into account decrease in an expression gastric mucin MUC1, MUC5AC and MUC6. The role of a genetic susceptibility of an organism to infected Н pylori, the factors of its pathogenicity promoting metaplasia epithelium is analyzed. Also role Toll-like of receptors 4 types (TLR4), participating in recognition Н. pylori is established. Development of the superfluous immune answer of the owner is connected with receptors of this type, leading to damage of a mucous membrane at Н. pylori-infected persons. In particular, carriers TLR4+896А>G polymorphism have heavier atrophy of a stomach and inflammation degree, and also the raised risk a stomach cancer.