Potential inversion of a single cell in a PEMFC stack reduces its performance and can lead to severe damage in the MEAs. Numerous causes of potential inversion can be considered, from MEA degradation to insufficient feed of reacting gases. The first part of the paper deals with experiments carried out to investigate whether the potential inversion could be suppressed by increasing the inlet gas flow. Then, the defective cell resistances were measured and compared to those exhibited by the other cells in the 23-cell stack. We also studied the influence of this cell on the whole stack resistances. Finally, the defective cell was dismantled and analysed, in order to explain where the defect comes from and whether it has affected each part of the cell. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.