Proton-exchange membrane (PEM) technology is commonly used for manufacturing water electrolysers, H(2)/O(2) fuel cells and unitized regenerative fuel cells. It can also be used to develop electrochemical compressors, for the purpose of concentrating and/or pressurizing gaseous hydrogen. The aim of the work reported here was to evaluate the main operating characteristics of a laboratory scale (approximate to 10 N liter/h) monocell compressor. The role of various operating parameters (current density, temperature of electrochemical cell, water vapor partial pressure in the hydrogen feed gas, anodic gas composition, etc.) has been evaluated and is discussed. It is shown that the relative humidity of hydrogen oxidized at the anode of the compressor should be adapted to the current density during operation to avoid mass transfer limitations or electrode flooding. A cell voltage of 140 mV is required at 0.2 A cm(-2) to compress hydrogen in one step from atmospheric pressure up to 48 bar, corresponding to an energy consumption of ca. 0.3 kW h/Nm(3). Experiments have been performed up to 130 bar. Series connection of several compressors is recommended to reach output pressures higher than 50 bar. To reduce gas cross-permeation effects which can negatively impact the efficiency of the compressor, additional experiments have been made using Nafion membrane modified by addition of zirconyl phosphate. Finally, data related to the extraction of hydrogen from H(2)-N(2) gas mixtures are also reported and discussed. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.