Two types of antitumor reactions in animals to chemical carcinogens have been analyzed: local and common. The first is manifested under the effects of dietary factors (fats and fibers), the second under the effects of antitumor vaccines. Fibers locally activate the functional activity of the gastrointestinal organs and increase their resistance to a carcinogen. The resultant high activity of the colon contributes to the more rapid removal of the carcinogen, decreasing the amount of time that it is present in the colon. Some fibers, such as cellulose, stimulate a local increase in the concentration of antitumorigenic enzymes, such as ODC and β-glucuronidase, in the mucus and feces. Experiments with mammary cancer have shown that the anti-tumorigenic effects of an olive-oil diet are connected to its content of monounsaturated fatty acids, such as oleic and palmitic acids. The tumor-promoting effects of other high-fat diets (avocado and soybean oils) were associated with their high content of polyunsaturated fatty acids, such as linoleic and α-linolenic acids. All of the parameters evaluated following consumption of the various diets reflect their local antitumor effects. The common reaction of animal immune systems to the carcinogenic effects of chemical carcinogens is reflected in the protective effect of the soluble tumor-associated antigens (sTAA). sTAA have both tumor-preventive and tumor-suppressive effects on chemically induced cancers of the colon, skin and mammary glands in rats and mice. sTAA promote the suppression of rat mammary tumors by different anticancer drugs, such as cyclophosphamide (CPA), tamoxifen and 5-fluorouracil (5-Fu), and decrease the drugs’ toxic side effects. This effect has been shown to be connected with activation of the host’s immune system, especially that part which is responsible for the activity of T and B lymphocytes.