In order to investigate the abrasion phenomena in a planetary ball mill, we conducted the grinding operation without a powder and sought a correlation between the ball abrasion and the ball impact energy estimated by a Discrete Element Method (DEM) simulation. Experimental results showed that the mass of abraded balls increased in proportion to the grinding time in the early stage of grinding up to 75 min. The abrasion rate increases quadratically with the mill rotation speed. It decreases with an increase in ball diameter up to 12.7 mm and then slightly increases when the diameter is 15.8 mm. It also increases with an increase in the ball-filling ratio of the mill up to 50%. Similar tendencies are found in the impact energy calculated from the balls motion simulated by DEM. Therefore, it is said that the abrasion rate has a strong correlation to the impact energy of balls under any milling conditions. (C) 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.