Methanol steam reforming (MSR) reaction to produce pure hydrogen has been studied, from an experimental point of view, in a flat Pd-Ag membrane reactor (MR). The membrane consisted of a pinhole free palladium-silver alloy, 60 mu m thick. In order to investigate the behaviour of methanol conversion in the MSR reaction carried out in MR, the influence of methanol feed flow rate, as well as the influence of the operating temperature have been analysed. The dependence of the increasing O-2/CH3OH feed ratio on the methanol conversion has been also studied. Experimental results in terms of methanol conversion as well as hydrogen permeation and CO selectivity for MR are proposed. Some experimental data concerning methanol conversion have been compared with the literature data. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.