Experimental investigations and numerical simulations with the discrete element method (DEM) were carried out to improve the understanding of the movement and mechanical interaction of particles in rotary kilns. The focus is on the bed movement in the rolling motion mode with rotational speeds varying between 3 and 15 rpm. Characteristic parameters for this system are the Froude number, the dynamic angle of repose, the thickness of the active layer and the particle velocity on the bed surface and at the wall. These parameters were measured in rotating drum experiments, computed in DEM simulations and compared with each other. When available, analytical and/or semi-empirical macroscopic models were included in the comparison. Both the DEM simulations and the analytical macroscopic models show good agreement with the experiments in general. The wide range of parameters considered, like drum diameter, particle diameter and rotational speeds, provide a comprehensive reference data set. (C) 2014 Elsevier B.V. All rights reserved.