The radioprotective properties of copper chlorophyllin, riboxin (inosine) and trolox (a water-soluble form of vitamin E) were studied after irradiation of outbred male mice of the ICR (CD-1) SPF category with X-ray radiation at a dose of 6.5 Gy. The test substances were administered intraperitoneally to mice an hour after irradiation, then the drugs were administered 3 more times at daily intervals. The volume of administered drugs was 0.32 ml. Dosages for each administration: trolox – 200 μg/g body weight, copper chlorophyllin – 50 or 100 μg/g, riboxin – 200 μg/g. Mice were euthanized 4 days after irradiation. Radioprotective efficacy was assessed based on 30-day survival and on the basis of the following indicators 4 days after irradiation: body weight, weight of the thymus and spleen, hematological indicators (leukocytes, lymphocytes, monocytes, granulocytes, erythrocytes, platelets, hemoglobin, hematocrit, thrombocrit), the number of nucleated cells in the bone marrow, the content of thiobarbiturate-reactive products in the liver. Irradiation caused a decrease in the mass of the thymus and spleen, the content of leukocytes and platelets in the blood, and the number of nucleated cells in the bone marrow. The studied substances, when using the given application scheme, did not contribute to an increase in these parameters. Irradiation led to an increase in the content of thiobarbiturate-reactive products in the liver of mice, which is a marker of lipid peroxidation caused by it. All studied substances contributed to a decrease in this criterion, except for chlorophyllin, administered at a dosage of 100 μg/g (total dosage 400 μg/g). However, only in this case was there an increase in survival compared to the irradiated control group. Trolox and riboxin contributed to a decrease in the content of end products of lipid peroxidation in the majority of mice from the corresponding group. However, in some of them this effect was not observed at all. The use of copper chlorophyllin in the regimen we used led to the appearance of signs of chemical poisoning in mice. We explain this by its manifestation of toxic properties due to the presence of a copper atom in its molecule. It seems promising to repeat the study using a chlorophyll derivative that does not contain copper.