The heat flow and heat generation from Precambrian areas has been examined with reference to the concept of heat-flow provinces. In nonshield areas of exposed Precambrian rocks, the heat flow is governed by Phanerozoic tectonic events, rather than by the age of the exposed rock. A plot of heat flow against heat generation of all data from shields yields a heat-flow intercept of 0.7 HFU, compared with 0.8 HFU for the Eastern U.S.A. Even within the stable Precambrian shields, heat flow is more closely related to rock type than to age of the rocks. The analysis supports the linear relation of heat flow to heat generation in shield areas.