The performance of 1 kW(el) 48-cell HT-PEMFC at various experimental conditions is presented, particularly at several CO concentrations (up to 1.0%). Polarization curves measured at various anode (1.0-2.5) and cathode (1.6-4.0) stoichiometries; stack operating temperatures (120-160 degrees C) and gas pressures (up to 0.5 bar(g)) are reported and analysed. The minimum gas stoichiometries of 1.25 and 2.0 were determined for the anode and cathode, respectively. The highest stack power density of 225 mW cm(-2) was measured at 160 degrees C and 0.4 A cm(-2). Operation at CO concentrations up to 1% was achieved, although a loss of performance of about 4% was observed for low CO concentrations. The operating temperature enhanced fuel cell performance and tolerance to CO, even when supplied with higher CO concentration in the anode feed gas. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.