Mercury (Hg) and selenium (Se) concentrations were determined by radiochemical neutron activation analysis in samples from the pituitary glands, occipital cortices, renal cortices, abdominal muscles, and thyroid glands of cadavers. Samples were retrieved from dental staff occupationally exposed to Hg and from the general population. Increased concentrations of both Hg and Se in samples from dental staff showed that Se accumulated together with Hg. Regression analysis of data from the pituitary glands and occipital cortices of dental staff indicated the accumulation of Se at a rough stoichiometric ratio of 1:1 with Hg. The same stoichiometric ratio between the elements was seen in the renal cortices from the general population. The regression analysis showed that a substantial fraction of Se was not associated with Hg; it is assumed that this corresponds to biologically available Se. Concentrations of biologically available Se decreased with advancing age in the pituitary gland, but not in other organs, and varied appreciably between organs.