Durability is one of the major barriers to proton exchange membrane fuel cells (PEMFCs) being accepted as a commercially viable product. It is therefore important to understand the degradation phenomena of MEA (membrane electrode assembly) in PEMFCs and analyze degradation mechanisms. This study adopted the accelerating degradation technique to analyze durability of PTFE/Nafion MEA using the Taiwan HS-150 fuel cell tester and MEN Stack Durability Protocol developed by the Fuel Cell Technical Team (FCTT) of the FreedomCAR and Fuel Partnership. The experimental process for the MEA degradation contains dry/wet and load cycling. During durability test of the MEA, the polarization curve, cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) are used for diagnosing state of the MEA. The experimental results show that failure of the proton exchange membrane is the decisive factor leading to the end-of-life of the MEA and the electrochemical reaction micro-structural damage of catalytic layer is the decisive factor of the performance degradation and stability deteriorates. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.