Prevention of cancer in high gastric cancer risk groups is in accordance with experimental and epidemiological studies reasonable. Primary prevention of gastric cancer however is apart of healthcare system equally a problem of ecology, agriculture, and traffic as well. Physician can appeal only in secondary prevention in high risk groups (atrophic gastritis with intestinal metaplasia, gastric polyposis, xantelasmas, gastric remnant after B II resection 10-15 yrs. after operation, chronic H. pylori infection). Restriction of smoked food (3,4-benzpyren), broiled meat (pyrolysates of protein, tryptophayn, phenylalanin), salt, aflatoxin B (Aspergillus flavus in silage, nuts etc.) and high consume of fruit, vegetables (A, C and E vitamins) and selen are acting as chemopreventive agents.