A simple criterion is presented to determine whether or not charged particles will adhere to the collecting plate in a wire-plate electrostatic precipitator (ESP). Based on the energy balance, it was determined that when a charged particle collides with the collecting plate, the charged particle will adhere to the collecting plate if its kinetic energy is less than the sum of its electrostatic energy and the surface energy between the charged particle and the collecting plate; otherwise, the charged particle will rebound off the collecting plate and continue to be transported and charged until it is captured or exits the collection zone of the ESP. With this criterion, a large number of particles with both high and low resistivity were tracked numerically in the ESP of Riehle (Proceedings of the Fourth International Conference on Electrostatic Precipitation, 1990, p. 136) and their grade efficiencies were computed. For particles with low resistivity, the present criterion is very useful for understanding the collisions between the charged particles and the collecting plate in the ESP. (c) 2004 Elsevier Ltd. All rights reserved.