The 18-months-old female rats received with drinking water Hg2(NO3) in concentration of 1 mkg/l in account to metal and a preparation of selenium "Neoselen" (Na2SeO2) in concentration of 1.3 ml/kg/day, respectively, during 1 month before and 1 month after single gamma-irradiations with 25 cGy doses. Are established early (through 24 h after an irradiation) cytologic and genotoxic reactions in leukocytes of blood, and also hematological, biochemical reactions and changes of the content and frame DNA of leukocytes of blood in 30 day after an irradiation? Features of action of low doses of radiation in a combination to ions of mercury and their combination with a preparation of selenium are revealed. Communication of postradiating effects--changes of indexes of DNA of leukocytes of blood with reduction of life expectancy of animals is shown. The data are received, permissive to draw the conclusion, that the preparation of selenium in utilised concentrations, essentially not influencing on lifetime at low doses of radiation--mercury affecting is capable to improve quality of life of elderly animals