Relationships between electrical and thermal conductivities of consolidated sandstone rocks and sediments were investigated. Equations are given which relate the two conductivities for the rocks, and thermal and electrical conductivities for sediments. Data from 65 rock samples and 105 sediment samples were used in establishing the reliability and parameter values of the equations. The derived equations can be used to determine thermal conductivities from electrical conductivities providing thermal conductivities of the solid constituents can be approximated. For samples of sandstone, deviations of data from values predicted by equations are shown to be related to variations in composition of the samples. Within the accuracy of the data, the thermal conductivities of sediment samples seem to be controlled more by the water content than by the mineral composition.