The electrical conductivity of oil shale from the Anvil Points Mine, Colorado, was measured to temperatures greater than 900supO/C with conductance bridges operating at frequencies from 100 to 100,000 Hz. The conductivity of low, intermediate, and high grade oil shales(15,124, and 233 ml/kg, respectively) is dependent on water content up to approximately 100supO/C. At about 120supO/C, values of conductivity around 10sup-7/S/m are observed for all grades. A strong, time dependent, increase in conductivity, beginning around 400supO/C, marks the loss of light hydrocarbons and the formation of a conductive char. The frequency dependence of conductivity--slightly less that a decade increase in conductivity per decade increase in frequency over the temperature range 100supO/C to 400supO/C--vanishes at temperatures near 500supO/C. At temperatures between 600supO/C and 800supO/C, the conductivity of these oil shales reaches a maximum value which is as much as 10sup8 times larger that the conductivity near 250supO/C.