In order to classify fine particles in slurry continuously, a horizontal type water elutriator with electrical potential is newly developed. The experimental classification performance was compared with the numerical calculation. Test particles used were pure silica particles with the mass median diameters of 3.5 and 2.5 mu m. The effects of inlet flow rate, slurry concentration, applied electro-potential and the shape of inlet on the classification performance were also studied. The classification accuracy increased by applying the electro-potential and the cut size decreased with an increase in the electro-potential The classification performance with a three-layer inlet was higher than that with a two-layer inlet. The experimental data agreed well with the numerical calculation. It is further shown that the 50% cut size was about 1 mu m for a relatively short time, and the newly developed water elutriator is, therefore, effective for the classification of fine particles in slurries. (C) 2009 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights reserved.