The comminution process in stirred media mills is not a static process. Characteristic comminution parameters like the stress energy can only be described by distributions. In addition, several energy dissipation mechanisms are the reason that only a small part of the energy which is transferred into the grinding chamber is used for the comminution process. It is shown a that the different comminution behaviours of stirred media mills of different types and sizes can be explained by an analysis of the distribution of the stress energy and the different energy dissipation mechanisms in the grinding chamber. Based on this analysis, a more accurate scale-up is possible especially for stirred media mills with disc stirrer. (C) 2004 Elsevier B.V. All rights reserved.