The Macmillan Pass in east-central Yukon (Figure 1) near the border with the Northwest Territories, is a highly mineralized area. The significant presence of metallic minerals in the MacMillan Pass area is reflected by the naturally elevated metal concentrations in both the soil and water (Soroka and Jack 1983, Kwong and Whitley 1993). A recent surge in metal prices has sparked renewed interest in mineral exploration and development at MacMillan Pass. Consequently, a broader understanding of the regional stream geochemistry is particularly important to help establish environmentally meaningful water quality objectives for the region.