Carcasses of the federally endangered subspecies of Mountain Beaver, Aplodontia rufa nigra, were recovered and necropsied. Metals chemistry revealed mean concentrations of copper (x ¯  =  1250.0, s  =  60.8 µg/g dry weight [dw]) and iron (x ¯  =  3573.3, s  =  2505.0 µg/g dw) in liver tissue that were in the range indicative of possible copper toxicosis and liver storage disease in other species. Normal ranges of metal concentrations in the tissues of Mountain Beavers, however, are unknown. Livers of trapped Mountain Beavers from other locations also showed high mean copper (x ¯  =  1035.3, s  =  612.3 µg/g dw) and iron (x ¯  =  8317.5, s  =  7985.6 µg/g dw) concentrations. Metals in soil and plant tissue samples collected from the territories of the necropsied animals were within expected ranges. These results suggest that copper and iron might be naturally higher in Mountain Beaver livers relative to other rodent species. However, the possibility that at least some of the animals exhibited a disease condition cannot be dismissed without further evaluation.