The changes in properties within membrane electrode assemblies (MEAs) aged in a stack functioning at constant-power operation (0.12 Wcm(-2)) for several durations (0, 347, 892, and 1397h) were characterized. An important effort was placed into better understanding interfaces. Two tests were thus developed to investigate the changes in each active layer/membrane interface. Both techniques demonstrated that the mechanical bounding of both cathode and anode to the polymer membrane improve with the functioning time in fuel cell. This phenomenon was further attributed to Pt dissolution and diffusion/precipitation within the polymer membrane and to a diffusion/crystallization of the binding agent in the vicinity of the electrode/membrane interfaces. (C) 2010 Elsevier B.V. All rights reserved.