Load-on/off cycles at 80 C, with near-saturated H-2 and air at ambient pressure were applied to investigate the durability of several types of membrane-electrode-assemblies (MEAs) for proton-exchange-membrane fuel cells (PEMFC). The ohmic resistance, H-2 cross-over, electrochemically active surface area (ECSA), protonic resistance of the cathode as well as the performances with H-2/air and H-2/O-2 were measured at regular-intervals. These data enabled a breakdown of the increase in cell voltage losses upon Cycling. Increase of kinetic losses was found in all MEAs but significant differences were obtained for the transport losses in the cathode catalyst layer, which either had a small or a substantial contribution to the overall voltage decay, depending oil the carbon type and ionomer loading. Membrane degradation did not contribute significantly in these tests. (C) 2009 Elsevier B.V. All rights reserved.