Experimental and modelling studies of particle separation from liquids using a dielectric force show that dielectrophoresis may be an appropriate mechanism for multipass filtration systems if the dielectric properties of the fluid and contaminant are favourable. The general trends in filtration efficiency have been identified through an experimental investigation. Higher filtration efficiency is obtained when the viscosity of the liquid is lowered, when the contaminant particle sizes are larger, when the collector particle sizes are smaller and when the concentration of particles in the feed is lower. Efficiency was almost independent of flow rate over the range studied. A model is developed to calculate filter efficiencies; although the general trends in the. variation of filter efficiency with process variables can be predicted, absolute values of the calculated efficiencies are too high; ways to improve the model are suggested. A filter design that can be scaled-up has been used in the experimental work, which has identified the main parameters in the process.