Landfilling used tires which are generated each year in the United States is increasingly becoming an unacceptable solution. A better approach, from an environmental and economic standpoint, is to thermally reprocess the tires into valuable products such as activated carbon, other solid carbon forms (carbon black, graphite, and carbon fibers), and liquid fuels. In this study, high surface area activated carbons (>800 m(2)/g solid product) were produced in relatively high yields by pyrolysis of tires at up to 900 degrees C, followed by activation in CO2 at the same temperature. The surface areas of these materials are comparable with those of commercial activated carbons. The efficiency of the activation process (gain in specific surface area/loss in mass) was greatest (up to 138 m(2)/g original tire) when large pieces of tire material were used (similar to 170 mg). Oxygen pretreatment of tires was found to enhance both the yield and the surface area of the carbon product. High-pressure treatment of tires at low temperatures (<400 degrees C) is an alternative approach if the recovery of carbon black or fuel oils is the primary objective.