From 1981 to 1983, concentrations dfof metals were determined in mink Mustela vison, muskrats Ondatra zibethica, and small mammals at one contaminated site in Idaho and at two less contaminated sites in Idaho and Washington. The highest concentrations of Pb and Cd occurred in samples from the Coeur d'Alene River system near or downstream from an extensive mining?smelting complex in northern Idaho. Maximum concentrations of Pb in the liver of a mink (22 :g g-1) and in pooled liver samples of both voles (Microtus spp., 5?8 :g g-1) and deer mice (Peromyscus maniculatus, 10?5 :g g-1) were higher than those inducing serious problems, including mortality, in experimental mammals on Pb-contaminated diets. Concentrations of Cd, Cu, Hg, and Zn were generally low. Declines in certain mammal populations have probably occurred in northern Idah as a result of direct toxicity of metals and associated secondary effects on cover and food supply.