Results of studies on wet grinding of ceramic masses in industrial and pilot-plant mills for different compositions of grinding media are presented in the paper. Results of the particle size analysis of ground raw materials enabled the determination of the process run, and in particular, changes of an average particle size in time. It was found that the rate of grinding of the tested materials, especially at the beginning of the process, depended on the size of grinding media and the effect of their number became noticeable when the mean particle size reached 30 mum.