The interaction of inorganic mercury (as HgCl2) with SeO2 and organic Se-compounds is compared. Instrumental neutron activation analysis (INAA) was applied as the analytical method. Organ concentrations of Hg and Se were always significantly higher after simultaneous i. p. injections with HgCl2 and Se-compounds. Especially high abundances of Se and Hg in mice organs were found after simultaneous injection with Se-methionine and HgCl2. We suggest that Hg2+ ions are bonded by selenohydryl groups of the metabolites of injected Se-compounds. Binding yield of Hg2+ ions with metabolites of Se-compounds depends upon the chemical form of injected Se-compounds. Variations in the content of Zn, Co, Fe and Rb were observed in all the investigated organs after a single injection with HgCl2 or Se-compounds. Simultaneous injection with HgCl2 and Se-compounds affects the contents of these elements in comparison with single injections.