The Discrete Element Method (DEM) has been used to simulate tumbling, vibration, centrifugal, and Hicom Nutating mills in mineral processing research, Information about mills such as power draw, torque, load behavior. velocity, impact force and energy can be produced by DEM simulation. It is a promising and potentially powerful vehicle for the design and optimization of mills. The validation of DEM simulation results has been carried out to a limited extent. This paper introduces a specially designed two-dimensional mill which is the prototype producing what the DEM simulates. The entire trajectories of a single ball at different mill speeds were recorded and the velocities before and after its impact with the mill shell were calculated, By comparing with the simulated trajectories and velocities, it is confirmed that the coefficient of friction of ball-wall, mu(bw) determines the toe and shoulder positions of the charge and the coefficient of restitution of ball-wall, e(bw), determines the bouncing velocity after impact. However, the simulation parameters (mu(bw), e(bw)) for the best fit to the experimental data are not the same as these with which the mill run stably during simulation. A lot of minor collisions were observed in the simulations, which were not found in previous simulations and experiments, The ability of DEM to fairly accurately model single-ball behavior is established. (C) 2002 Elsevier Science B.V. All rights reserved.