Characterizing the hydrodynamics of a fluidized bed is of vital importance to understanding the behavior of this multiphase flow system. Minimum fluidization velocity and gas hold up are two of these key characteristics. Experimental studies addressing the effects of bed height and material density on the minimum fluidization velocity and gas hold up were carried out in this study using a 10.2 cm diameter cylindrical fluidized bed. Three different Geldart type-B particles were tested: glass beads, ground walnut shell, and ground corn cob, with material densities of 2600, 1300, and 1000 kg/m(3), respectively. The particle size range was selected to be the same for all three materials and corresponded to 500-600 mm. In this study, five different bed height-to-diameter ratios were investigated: H/D 0.5, 1, 1.5, 2, and 3. Minimum fluidization velocity was determined for each H/D ratio using pressured rop measurements. Local time-average gas hold up was determined using non-invasive X-ray computed tomography imaging. Results show that minimum fluidization velocity is not affected by the change in bed height. However, as the material density increased, the minimum fluidization velocity increased. Finally, local time-average gas hold up values revealed that bed hydrodynamics were similar for all bed heights, but differed when the material density was changed. (C) 2011 Elsevier Ltd. All rights reserved.