A metabolic model for cadmium has been formulated in terms of a flow scheme for cadmium among eight body compartments. The mathematical description of the flow of cadmium between compartments consits of a number of differential equations, and the accumulation of cadmium may thus be calculated. Coeffcients for the flow of cadmium were estimated from empirical data both from animals and man. The modelling serves two main purposes: it provides a means of using present knowledge about metabolism in order to calculate expected accumulation in critical organs and other tissues and body fluids at certain intake levels and it makes it possible to define deficiencies in our present knowledge about metabolism. Data recently collected, partly as a result of considerations related to the model, have confirmed the assumptions of a very long biological half-time in other tissues and the small excretion of cadmium via bile.