Pressure fluctuations in a fluidized bed (0.38 m-I.D.×4.4 m-high) of 1.23-mm polymer particles (LLDPE) were measured with different distributors. Slug characteristics (slug frequency and slug rising velocity) were determined by analyzing pressure fluctuations in the bed. The effects of gas velocity (0.6-1.2 m/s) and distributor geometry (opening area ratio, number of orifices and distributor types) on the slug characteristics were determined. The slug frequency decreases slightly with increasing gas velocity. However, slug rising velocity increases linearly with increasing excess fluidization velocity regardless of the distributors used.