In continuation of works on toxicology of nanocarbon materials, investigations of safety of colloidal gold nanoparticles in the 10 to 40 nm size range in two lines of mice (outbred and line C57BL/6j) were performed. It was shown that in 24 h and 30 days after a single parenteral injection of colloidal gold nanoparticles in mice, the toxic action on indicators of peripheral blood, behaviour of animals, as well as internal organs was not revealed