The effects of fluidization conditions on the membrane permeation rate in a membrane assisted fluidized bed (MAFB) employing micro-porous membranes have been studied experimentally in a square fluidized bed, equipped with vertical ceramic membranes positioned in a staggered arrangement. First, the morphological parameters of the membranes have been determined with separate experiments and the membrane gas permeation rates could be well described with the dusty gas model. Secondly, the effects of the fluidization conditions, such as the particle size, superficial gas velocity and freeboard pressure on the membrane permeate flow rate have been measured. The membrane permeation rates from the fluidized bed could be well described by taking into account the local pressure drop over the membrane, where the local pressure inside the fluidized bed was evaluated as the hydrostatic head using the average bed porosity. (C) 2003 Elsevier B.V. All rights reserved.