The porous carbon with high specific surface area (more than 3000 m(2)/g) was prepared by activating the combined rice husks by using potassium hydroxide and sodium hydroxide as activating agents. The effects of preparation parameters on the properties of the porous carbon were studied. the mechanism and the difference between KOH and NaOH were discussed through the pore size distribution. (C) 2002 Elsevier Science B.V. All rights reserved.