The insufficient long-term durability of polymer electrolyte membrane fuel cell (PEMFC) stacks has been blocking commercialization of PEMFC technologies. An accelerated degradation test (ADT) is needed to facilitate the PEMFC development process by reducing the testing time. We propose an ADT procedure for a PEMFC stack with the concept of series reliability structure under startup-shutdown cycling testing conditions. The acceleration factor is estimated to fit the degradation paths of individual cells consisting of the PEMFC stack under normal use conditions via the accelerated degradation data of a single cell. We employ a nonparametric regression method to smooth the degradation curves observed from accelerated operating conditions. We illustrate the methodology for estimating the lifetime of the PEMFC stack using the theory of the smallest-order statistics. We propose a three-parameter Weibull distribution in fuel cell technology to fit the failure data of cells in a PEMFC stack. (C) 2014 Elsevier Ltd. All rights reserved.