Kinetic models for the distribution and elimination of certain trace metals in mammals allow evaluation of metal burdens in critical target organs under time-variables exposure patterns, and thus may assist in formulating exposure standards. The linear compartmental model is described and some of its implications for conceptual models of trace metal metabolism are developed. The model is then applied to data on multiple doses of cadmium in mice. Many trace metals do not follow simple linear kinetic models because exposure to more than one metal simultaneously often results in synergistic effects.