Laboratory studies of the electircal conductivity of rocks and minerals are vital to the interpretation of electromagnetic sounding of the Earth's mantle. To data, the most reliable data have been collected from single crystals. We have extended these studies with electrical conductivity measurements on a dunite from North Carolina, in the temperature range of 600¿ C--1200¿ C and under controlled oxygen fugacity. Observations of conductivity as a function of oxygen fugacity and temperature demonstrate that conduction in the dunite is indistinguishable from conduction in single olivine crystals. Thus the common practice of exaggerating the single-crystal conductivities to account for conduction by grain boundary phases in the mantle is unnecessary. Because the dunite conductivity is consistent with that published for single crystals under similar conditions, we have made a combined analysis of these data. Conductivity as a function of temperature between 600¿ and 1450¿ C displays three conduction mechanisms whose activation enegies may be recovered by nonliner least squares fitting, yielding activation energies of 0.21¿2.56¿10-19 J(0.13¿1.60 eV) below 720¿ C 2.56¿0.02¿10-19 O2J(1.60¿0.01 eV) between 720¿ C and 1500¿ C and 11.46¿0.90¿1019 J(7.16¿0.56 eV) above 1500¿ C. The behavior of conductivity as a function of oxygen fugacity is well explained by a model in which an fO-2 -independent population of charge carriers is supplemented at high oxygen fugacities with a population that is proportional to fo20.3. This parmetrization produces a clear correlation of the fo2 dependent term with iron content, which is otherwise obscured by variations in conductivity among olvines. ¿ American Geophysical Union 1990