Two-dimensional structures of polymer (polystyrene) colloidal particles were formed on a substrate by electrophoretic deposition in an aqueous suspension. The prepared suspension is stable for a few days; therefore, it was not necessary to place an additional mixing during the deposition process. The particle aggregation/disaggregation formation was observed on the metal surface in order to study the effect of pulse direct current (DC) charging in comparison with conventional DC charging. At the charging frequency of 80 Hz, it was observed that pulse DC charging with a maximum applied voltage of 3.3 V/cm (50% duty cycle) clearly reduced the degree of aggregation of particles having diameters of 50 and 300 nm comparing to those of DC charging. Pulse charging at high frequency is thus found to be more effective in preventing particle aggregation during electrophoretic deposition than conventional DC charging. (c) 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.