This work investigates the production of pure hydrogen by steam methane reforming in a fluidized bed membrane reactor. Hydrogen is separated though palladium based dense membranes from the products of steam methane reforming reaction in a fluidized bed containing a catalytic partial oxidation (CPO) catalyst. First, a 2 weeks run test was performed assessing the reactor stability during the whole test and the membrane perm-selectivity (H-2/other gases) remained 100% even operating at elevated temperatures (903 K) and under bubbling fluidization regime. As the reactor demonstrated to be reliable and the membrane stable for a long period, a parametric study has been carried out highlighting the reactor performances in terms of methane conversion and hydrogen permeation. Moreover, the deviation from ideal reactor operation is outlined by studying the approach to equilibrium conversion and its connections with operating conditions. The operating conditions tested varied in the 773-903 K temperature range and 2.0-5.3 bar reacting pressure. The effect of weight hourly space velocity, steam to carbon ratio and dilution of the reacting mixture with an inert gas on the reactor performance were also investigated. Experimental results show that higher temperatures and pressures have positive effect both on approach to equilibrium conversion and on hydrogen yield, while opposite effects arise from increasing steam to carbon ratio and weight hourly space velocity. (C) 2013 Elsevier B.V. All rights reserved.