The effect of fine particles on the elutriation rate of the coarse particles at the gas exit was investigated in a gas-fluidized bed (i.d.: 0.1 m, height: 1.97 m) with sand as bed material. The elutriation rate of the coarse particles increased with the gas velocity and the proportion of fine particles in the bed. It was found to increase nearly proportionally with the upward momentum of the fine particles calculated on bases of unit mass and composition of bed particles at a specified gas velocity. The effect of the fine particles on the elutriation of the coarse particles decreased as the gas velocity increased. The elutriation of the fine particles was not affected by the size distribution of bed particles. An improved correlation to determine the elutriation rate of the coarse particles has been proposed for sand particles. (C) 2001 Elsevier Science B.V. All rights reserved.