Nafion degradation in polymer electrolyte fuel cells from SS316L end plate iron contamination was tested in a single cell configuration. Water collected at the cathode and anode exhausts was analysed by means of pH measurements, conductivity, fluoride and metal concentration. The investigations revealed that stainless steel is unsuitable as material for end plates in PEM fuel cells. In fact, iron contamination of membrane electrode assemblies led to polymer degradation, revealed by a massive fluoride loss. In contrast, iron-free plates (aluminium alloy) showed higher stability in the cell environment. (C) 2003 Elsevier Science Ltd. All rights reserved.