This contribution presents the preparation, permeation and stability study of mixed protonic-electronic conducting membranes based on the system Nd(5)LnWO(12). The tung-states Ln(6)WO(12) are proton conducting crystalline materials, which show sufficient protonic and electronic mixed conductivity and stability in moist CO2 environments to consider them as potential candidates for the separation of hydrogen at high temperatures. Hydrogen separation properties of A-substoichiometric Nd6WO12 and Nd5LaWO12 were systematically analyzed, i.e. the influence of the H-2 concentration in feed stream, humidification degree and operating temperature on the hydrogen separation was studied. Finally, the stability of these materials at different temperatures and CO2-rich and sulfurcontaining environments was evaluated. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.