The reaction kinetics between CO2 and residual carbon from Colorado oil shale (Mahogany Zone) have been investigated using both isothermal and nonisothermal methods. It was found that oil-shale residual carbon is approximately an order of magnitude more reactive than subbituminous coal char although the surface areas are similar. The reactivity of the residual carbon was found to carry by a factor of two for samples prepared by retorting the shale at heating rates between 0.033 and 12 degrees C min. Since the surface area of the residual carbon is approximately independent of the amount of oil coking, the heating rate effect cannot be explained by pore filling. Surface areas of the residual organic carbon in shale were estimated by comparing the surface area of retorted shale with that of retorted shale which has been declared by oxidation at 400 C. Surface areas of 250-400 m/g and 100-200 m2/g were obtained using CO2 and N2 respectively as the absorbed gases. Mercury porosimetry results are also presented.