Bed expansion characteristics in Newtonian and non-Newtonian fluid-solid two-phase fluidized bed have been examined. Bed expansion measurements were carried out for a bed of glass beads fluidized in Newtonian liquids (water and glycerol solutions) and non-Newtonian liquids (aqueous solutions of carboxymethyl cellulose (CMC) and xanthan gum). Measurements of bed voidage covered a terminal particle Reynolds number from 8.14 to 3947 and a flow index in a power-law model from 1 to 0.625. The bed voidage increased with an increase in the superficial liquid velocity and the magnitude of the increase became smaller as particle size increased. increase in viscous non-Newtonian flow behaviour resulted in an increase of the bed voidage. The generalized correlation for the bed voidage was developed for Newtonian and non-Newtonian liquid-solid two-phase systems by extending the correlation of the drag coefficient for single particles to multiparticle systems. The predictions for bed voidage were in reasonable agreement with the present experimental data and the data in the literature for Newtonian and non-Newtonian liquid-solid two-phase systems in the whole Reynolds number region.