Measurements of radiogenic heat production are presented for most of the major sedimentary formations beneath the rifted continental margin off Nova Scotia, Canada. The measurements were made on 32 samples from 14 deep exploratory wells drilled in the area. The results show that heat production ranges from about 1.8 to 0.3 µW m_-3, and varies with lithology. The 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°F (17°C), respectively. These temperature changes will increase the rate of organic maturation, so that, for example, oil generation should occur 10 to 30 Ma earlier in Jurassic sediments than if those sediments exhibited no heat production. It is noted, ho ever, that other thermal properties of the sediments must be studied before predictions of organic maturation and the timing of oil generation can be considered reliable. The results presented here show that radiogenic heat production in sediments is an important parameter in making reliable predictions of their thermal maturity and thus should be included in future studies of thermal models for sedimentary basins.