Dampier, L., Sanborn, P., Smith, S., Bond, J. and Clague, J. J. 2011. Genesis of upland soils, Lewes Plateau, central Yukon. Part 1: soils formed on Pleistocene glacial deposits. Can. J. Soil Sci. 91: 563-578. We describe and interpret nine upland (>1000 m asl) Dystric Brunisols and one Humo-Ferric Podzol formed on till of the McConnell [Marine Isotope Stage (MIS) 2] and penultimate (MIS 4 or 6) glaciations on the Lewes Plateau of central Yukon Territory. Unlike soils formed on correlative glacial deposits at lower elevation in the nearby Tintina Trench, the soils on the Lewes Plateau display only weak age-related differences. Penultimate and McConnell soils have solum thicknesses of 50-75 cm and <50 cm, respectively, but other morphological and chemical properties do not differ between the two age groups. Smectite is present in the McConnell soils; it was previously reported only in soils formed on Early Pleistocene glacial deposits in central Yukon and was interpreted to reflect weathering and soil formation during warm interglaciations. Paleoclimatic interpretations of clay mineralogy in central Yukon may be confounded by differences in parent material provenance and should be reassessed. This study shows that field soil characteristics alone are insufficient to differentiate McConnell and penultimate glacial deposits in upland landscape positions on the Lewes Plateau.