Nickel concentrations were measured in leaves of canopy and subcanopy trees from two nickeliferous areas in western North Carolina. Over and downslope from the Buck Creek ultramafic body in Clay County, the geometric mean of Ni concentrations is 250 μg/g in leaf ash, and only 3 out of 22 values are less than 100 μg/g. The geometric mean from trees growing over the surrounding mafic rocks is 65 μg/g, and only one value exceeds 100 μg/g. Results from the Webster-Addie district in Jackson County are less consistent, but in one oak species higher Ni values occur in samples taken over or near the ultramafic rocks. The more complete Buck Creek results suggest that differences in Ni concentrations between species are less important than differences between plants in nickeliferous and non-nickeliferous areas. The ability of plants to assimilate nickel provides a potential prospecting tool for this element in humid temperate forests.