The interaction of Cd (as CdCl 2) with organic Se-compounds and SeO 2 was investigated. Instrumental neutron activation analysis was applied as the analytical method. Concentration of Se in liver and kidneys were always significantly higher after simultaneous i.p. injections with Cd and Se-compounds in comparison with single Se-injection. Cd or Se-injections also affect the content of Zn, Fe, Co and Rb in all the investigated organs. We suggested that the formation of Cd-Se-protein complexes allow for an orderly transfer of Cd to metallothionein (MT). The results showed that Cd was a very effective inducer of MT, and the maximum formation of MT was observed in the liver.