The individual phase holdups in two (liquid-air, liquid-solids)and three (liquid-air-solids) phase fluidized beds have been measured ovr a wide range of liquid and gas velocities. Experiments were carried out in a large two-dimensional bed. Three solids were used ranging in size from 1 to 6 mm. The effect of viscosity (1-70 cp) was determined using solution of sugar and carboxymethyl cellulose of different concentrations. Various acetone tension in the range 44-73 dyne/cm. Beds of particles having a minimum fluidzing velocity in the liquid of less than 1.28cm/s were found to initially contract upon the injection of gas In contrast, beds of particles having minimum fluidizing velocitiess excedding this value were found to expand