Perfluorinated sulfonic acid proton exchange membranes are in the forefront as solid electrolytes for fuel cell applications. Although expensive, its potential utilization in commercial fuel cells can be validated provided it can be established that it is highly durable. In this context, peroxide radical-initiated attack of the membrane electrode interface is one of the key issues requiring further systematic investigation under fuel cell operating conditions, to better determine the fundamental degradation mechanism. In this study, we attempt to analyze the durability of the membrane electrode assembly (MEA) made with different commercial electrodes from the perspective of peroxide radical-initiated chemical attack on the electrode/electrolyte interface and find the pathway of membrane degradation as well. A novel segmented fuel cell is employed for durability characterization, and use of this cell and pre and post analysis of the membrane are presented. Correlation of membrane degradation data with the peroxide yield determined by RRDE experiments is obtained. This method is able to separate the membrane evaluation process into cathode and anode aspects. Fenton type mechanism of pet-oxide radical generation from H2O2 formed due to two-electron pathway of ORR is found to be the dominant membrane degrading factor. (C) 2007 Elsevier Ltd. All rights reserved.