In recent years, there has been a rapid advancement in the understanding of tumbling mills through computer simulation using the discrete element method (DEM). It has thus far been able to qualitatively capture the behavior of the charge in ball, semi-autogenous, planetary, and many other types of tumbling mills. Quantitatively, it also allows accurate predictions of individual particle trajectories, distribution of contact forces and energies between collisions, wear, and most importantly, power draw. This review critically evaluates the understanding of the three important areas of the simulation aspect: the inter-particle force laws, significance and choice of contact parameters, and finally implementation of the numerical scheme. With the correct material properties and operating parameters, it is now possible to make useful predictions as to how tumbling mills perform. (C) 2003 Elsevier Science B.V All rights reserved.