Gypsum is an industrial material used in many applications such as building and chemical industry, fertilizer manufacture, medicine and dentistry. In these industries, there is need for finely ground gypsum. Energy consumption is very high in grinding processes. Therefore, the effects on breakage kinetics of powder filling and ball filling were investigated on gypsum samples taken from the Denizli-Honaz region (Turkey), for batch grinding conditions based on a kinetic model. For this purpose, firstly, eight different mono-size fractions between 1.7 mm and 0.106 mm formed by a root 2 sieve series were obtained. Then, S-i and B-ij equations were determined from the size distributions at different grinding times, and the model parameters (S-i, a(tau), alpha, gamma and phi(j)) were compared for five different proportions of powder filling (5%, 7.5%, 10%, 15% and 20%), and three different proportions of ball filling (25%, 35% and 45%). Finally, model parameters are discussed for each test. From the result of tests, obtained of the effect of ball filling and powder filling on the grinding, it was found our results differed from those of other investigators. (C) 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.