Temperature measurements in two drill holes near Lac de Gras in the Slave Province of the Canadian Shield yield heat flow values of 43 ¿ 5 and 48 ¿ 8 mW m-2 with an average of 46 ¿ 6 mW m-2. Heat production measured on samples from one of these holes is relatively high (1.9 ¿W m-3) confirming measurements made on outcrop samples. The surface heat flow and heat generation data imply that below a 10 km thick radioelement enriched layer, heat production is comparable to that in other Archean Provinces of the Canadian Shield. The lithospheric geotherm is very close to the geotherms derived from geothermobarometry on xenoliths. Variations in crustal heat generation account for ≈50 K differences in Moho temperatures within the Slave Province.