In this experimental work, a dense tubular Pd-Ag membrane reactor is used for carrying out the methanol steam reforming reaction for producing a CO-free hydrogen stream. A non-commercial Cu/Zn/Mg-based catalyst is used in the lumen side of the membrane reactor and the experimental tests are performed at a reaction temperature of 300 degrees C and H2O/CH3OH feed molar ratio of 3/1. In both co-current and countercurrent flow configurations, the effect of the weight hourly space velocity (WHSV) as well as the reaction pressure on the membrane reactor performances in terms of CO-free hydrogen recovery, hydrogen yield and hydrogen selectivity are proposed and discussed. (C) 2008 Elsevier B.V. All rights reserved.