The durability of proton exchange membrane fuel cells is one of the key issues hindering their widespread commercialization. This study uses the complex accelerating degradation protocol to investigate the performance decay of a membrane electrode assembly. The complex accelerating protocol includes OCV, RH cycling and load cycling. Linear sweep voltammetry, cyclic voltammetry, AC impedance and polarization curves were used to measure key MEA characteristics. The experimental results in this work revealed that the Nafion (R) film underwent significant thinning after the 1040th cycle. Moreover, during accelerated degradation testing, the electrochemical surface area decreased and was therefore found to be the main factor affecting the performance decay of the MEA. Copyright (C) 2010 John Wiley & Sons, Ltd.