The milling behaviour of microcrystalline cellulose (MCC) and alpha-lactose monohydrate (alphaLM) in an oscillatory single ball mill has been analysed by using the Distinct Element Method (DEM). The experimental results suggest that the milling behaviour of alphaLM is more strongly influenced by the milling frequency as compared to MCC. A similar conclusion is also drawn from the DEM results. The milling behaviour of MCC and alphaLM is described by a first order rate process, and its rate constant, K-p, is found to correlate very well with the milling power, P-n, determined by the DEM simulation, except for the milling behaviour of alphaLM at 18Hz. For the latter, there appears to be an incubation time after which the milling rate increases substantially. The results presented here provide a basis for predicting the milling behaviour of a material systematically based on the fundamental material properties and the machine dynamics without the need for extensive experiment and use of large quantities of materials. (C) 2004 Elsevier Ltd. All rights reserved.