Four main styles of quartz veining are recognized in the Klondike District. These include foliaform and discordant mesothermal quartz veins in schistose metamorphic rocks, quartz-carbonate veins in altered ultramafic rocks and greenstones, epithermal chalcedony veins cutting Eocene igneous and sedimentary rocks, and low-temperature epithermal veins associated with intensely altered Plio-Pleistocene White Channel Gravel deposits. Foliaform mesothermal quartz veins are invariably barren; however discordant mesothermal veins locally contain visible gold. Both styles of epithermal veins in the Klondike contain at least geochemically anomalous levels of gold. The complex history of hydrothermal activity in the Klondike has led to considerable confusion about the nature of veining in this area. The results of this study provide a preliminary framework within which to evaluate the various prevailing theories regarding the major sources of gold in the Klondike placer deposits.