The electrical conductivity of 7 dunites (Addie, ¿heim, Balsam Gap, Corundum Hill, Dun Mountain, Mooihoek and Twin Sisters) in the pressure range 12.5-45 GPa has been studied using the shock wave technique. In this pressure range the measured conductivity varies from 2.8⋅10-5 to 2.6⋅10-2&OHgr;-1cm-1. Differences in the total olivine content, Fe-content of the olivines, Fe2O3- and chromite content and grain sizes of the dunites lead to differences in their conductivity. All dunites show an increase of about 105&OHgr;-1 cm-1 of the electrical conductivity in the pressure range 0-40 GPa, thus approaching semiconductor behavior. This increase is due to both temperature and pressure effects and possibly also to a partial phase transition of olivine.