Information about the body burden of a metal is important in the evaluation of both exposure and risk. In vivo methods for determining cadmium and lead have become available in the last 20 years. Thus cadmium in kidney can be assessed by neutron activation or X-ray fluorescence analysis. The X-ray fluorescence technique allows kidney cadmium determinations even in subjects without occupational exposure. The level reflects the burden, long-term exposure, and the risk of toxic effects. Furthermore, in vivo determination of lead in finger bone, tibia, or calcaneus by X-ray fluorescence indicates long-term exposure and should become a valuable tool in epidemiologic studies, especially of chronic effects.