Activated carbon was prepared from rice hulls using potassium hydroxide as an activation agent. The effect of process variables such as carbonization, activation temperature, and chemical ratio of KOH to char on the pore structure and activation yield of the carbons was studied. High-quality activated carbons with high surface area, high pore volume, and well-developed pore structure could be prepared, when the char produced by the carbonization of rice hulls in a stream of nitrogen at 700℃ was well mixed with a concentrated solution of potassium hydroxide at a KOH : char ratio of 4 : 1 and then the mixture was activated fur 3 hours at 850℃ in a stream of nitrogen.