This map shows color-coded contours of the global distribution of heat flow at the surface of the Earth's crust. Major plate boundaries and continent outlines are also shown. The fundamental data embodied in this map are the more than 24,000 field measurements in both continental and oceanic terrains, supplemented by estimates of the heat flow in the unsurveyed regions. The estimates are based on empirically determined charactersitic values for the heat flux in various geological and tectonic settings. Observations of the oceanic heat flux have been corrected for heat loss by hydrothermal circulation through the oceanic crust. The global data set so assembled was then subjected to a spherical harmonic analysis. The map is a representation of the heat flow to spherical harmonic degree and order 12.