A systematic investigation of elutriation of particles is reported in the cold model of bubbling fluidized bed (BFB) and vortexing fluidized bed (VFB) of 0.19 m diameter and 4.0 m height. Class heads were used as the fluidized material. The diameter of the coarse particles was 545 mu m, the diameter of the fine particles used for the elutriation test ranged from 49 to 194 mu m. The results indicate that the specific elutriation rate constant (K-infinity*) is a function of the initial concentration of elutriated fine particles. The minimum value of K-infinity* is obtained when the initial concentration of elutriated fine particles is reached 16 wt% in a BFB system. Based on the experimental data obtained from the BFB. a correlation is presented to estimate the K-infinity*. The K-infinity* is found to be a function of the particle terminal velocity, gas density, and modified Froude number (Fr*). For a wide particle size distribution (PSD)system, a new parameter, called particle size distribution factor, gamma,is introduced to describe the specific elutriation rate constant of wide PSD elutriated fine particles. A method to estimate the specific elutriation rate constant of a multi-component system by using the specific elutriation rate constant of each component obtained from a binary particle mixture system is also presented in this study.