Electrical conductivity measurements of perovskite and a perovskite-dominated assemblage synthesized from pyroxene ((Mg0.88Fe0.12)SiO3) and olivine ((Mg0.88Fe0.122SiO3) demonstrate that these high-pressure phases are insulating to pressures of 82 GPa and temperatures of 4500 K. Assuming an anhydrous upper mantle composition, our result provides an upper bound of 10-2 S m-1 for the electrical conductivity of the lower mantle between depths of 700 and 1900 km. This is 2 to 4 orders of magnitude lower than previous estimates of lower-mantle conductivity derived from studies of geomagnetic secular variations. ¿ American Geophysical Union 1987