On the basis of an analysis of data from the literature and our own experimental results, the conclusion can be drawn that there is inverse linear dependence between the dose of irradiation and natural resistance of the organism to infection with various infectious agents. With increasing doses of irradiation, the irradiated organism is exposed to greatest risk from the part of the agents of intestinal infections and representatives of normal microflora. These are followed by agents of various diseases of microbial nature. The least decrease can be observed in resistance to viruses.