Off Nova Scotia, 32 samples from 14 deep exploratory wells. Heat production ranges from about 1.8 to 0.3 mu W m (super -3) , and varies with lithology. Effect of this radiogenic heat production is to increase the heat flow and the temperatures within the sediments by up to 15% and 30.6 degrees F (17 degrees C), respectively. These changes will increase the rate of organic maturation, so that oil generation should occur 10 to 30 Ma earlier than if those sediments exhibited no heat production. Other thermal properties must be studied before predictions can be considered reliable. Radiogenic heat production in sediments should be included in future studies of thermal models for sedimentary basins.--Modified journal abstract.