The characteristics of elutriation of fine particles and the effect of operating conditions on elutriation in a Powder-Particle Fluidized Bed were clarified using silica sand and activated alumina beads with a diameter of 550, 780 and 920 mu m as coarse particles, and Al(OH)(3) with a diameter of 3 and 15 mu m as fine particles. Fine particles were fed continuously to the bed and data were obtained under steady state. The elutriation rate constant of fine particles increased with an increase in gas velocity and the size of fine particles, and decreased with an increase in the size of coarse particles. However, it was not affected by the hold-up of fine particles. In the case of using fine particles having particle size distribution from 1 to 70 mu m and average particle diameter of 15 mu m at a gas velocity of 0.8 m/s, measurements of particle distribution of feed particles and entrained particles revealed that particles with a diameter over 30 mu m entrained selectively from the bed and particles with a diameter less than 8 mu m were held easily in the bed. It was suggested that this phenomenon could be explained by the relationship between cohesion forces of fine particles and the pressure of coarse particles based on the motion of coarse particles in the bed.