The electrical conductivities of two silicate perovskites and a perovskite-magnesiow¿stite assemblage, all having an atomic ratio of Mg to Fe equal to 0.88/0.12, have been measured with alternating current and direct current (DC) techniques at simulatneously high pressures and temperatures. Measurents up to pressures of 80 GPa temperatures of 3500 K using a laser-heated diamond anvil cell demonstrate that the electrical conductivity of these materials remains below 10--3 S/m at lower mantle conditions. The activation energies for electrical conduction are between 0.1 and 0.4 eV (0.1--0.2 eV most probably) from our data, and we ascribe the conduction in these perovskites to an extrinsic electronic process. Our new measurements are in agreement with a bound that was previously obtained from DC measurements for the high PT conductivity of perovskite-dominated assemblages. The results show that the electrical conductivity of (Mg0.88Fe0.12)SiO3 perovskite differs significantly from that of Earth's deep mantle, as inferred from geophyscial observations. ¿ American Geophysical Union 1990