The influence of several grinding parameters such as charged material volume, ball filling ratio, and mill rotation speed on energy efficiency of fine grinding of hydrated lime and the product fineness of hydrated lime was studied experimentally using a laboratory scale ball mill. The product size and surface area of the ground samples were determined with respect to the above variables, and changes in energy input during the grinding were described in detailed. Finally, the optimum conditions for the grinding of the hydrated lime with the ball mill were obtained. The results from this study showed that the ball mill load and mill speed are the most important parameters rather than ball mill charged material volume for the fine grinding of the hydrated lime using the ball mill in terms of energy efficiency associated with external surfaces. (C) 2012 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.