Cost and durability are major challenges for the commercialization of proton exchange membrane (PEM) fuel cells. Accordingly, there remains a need to understand the degradation of fuel cell components to mitigate or eliminate such degradation. Carbon support corrosion and Pt dissolution/aggregation are considered as the major contributors to the degradation of the carbon-supported Pt/Pt alloy catalysts. In this paper, a simple but effective test protocol is proposed in order to accelerate the lifetime testing of PEM fuel cells. An EIS diagnostic protocol has been used along with the standard potential cycling protocol to evaluate the degradation resistance of two different carbon catalyst materials and structures within an insignificant time period. Here we demonstrate how changes in the EIS response are indicative of specific modes of degradation. Thus the addition of EIS testing to accelerated durability protocols is highly recommended for all those studying catalysts layer durability. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.098205jes] All rights reserved.