Potential profile in PEFC electrolyte membrane has been investigated by using microprobe technique in order to help understand membrane degradation mechanism. In particular, potential distribution in the membrane under several operation conditions has been measured by using microprobes inserted in the membrane. A theoretical model has been developed to predict the potential distribution under different cell current density with cells of different rib/channel width. The model showed good agreement with experimental result. (C) 2012 Elsevier Ltd. All rights reserved.