A study was conducted to make activated carbon adsorbents using local rice hull ashes. As the carbonization temperature of the rice hull was increased, the specific surface area of the char increased steadily. The specific surface area of the char was enhanced either by boiling water washing, or by silica leaching using sodium hydroxide. When sodium hydroxide was used to leach out silica from the char, the specific surface area and the amount of silica removed increased most when the sodium hydroxide leaching was conducted in several stages. Activated carbon was also prepared from the rice hull by chemical activation method using phosphoric acid. The adsorption characteristics of phenol onto the activated carbons prepared were measured in a batch reactor. These results showed that as the specific surface areas of the activated carbons increased, better adsorptivities to phenol were obtained. The relationship between the amount of phenol adsorbed and equilibrium concentration was found to be well represented by the Freundlich isotherm. The adsorption capacity of the activated carbon prepared through chemical activation method was slightly better than that of the commercial product of Calgon F300.