This paper presents a model of the separation process in a ferrohydrostatic separator which has been designed and developed at TSS Technology, De Beers, South Africa. The model was developed using special Discrete Element Method software package called PFC2D (Particle Flow Code in 2D). The software models in 2D the movement and interaction of circular particles by the discrete element method. The simulation that was carried out using particles of different densities and sizes has proved that interactions among particles are the most important factor leading to the misplacement of particles. The theoretical results are then compared with the experimental results obtained in the De Beers FHS machine. The comparison has shown that the DEM model can predict the experimental results very well and can also accurately describe mechanisms of misplacements of the particles. (c) 2004 Elsevier Ltd. All rights reserved.