Nafion ionomer is impregnated or incorporated in the PEM fuel cell electrodes to achieve high power density. Though many studies have been reported on the effect of Nafion content on electrode performance, best results have been reported at different Nation loadings by different researchers. Nation ionomer helps to increase the three-dimensional zone of catalytic activity and platinum utilization in the electrode. It also helps to retain moisture and prevent membrane dehydration especially at high current densities. An optimum Nafion content in the electrode is necessary to achieve high performance. As the platinum loading increases, the electrode thickness and Nation thickness grows and hence the optimum Nation content may depend on the platinum loading. In this paper, we have examined the correlation of platinum loading and optimum Nation content in the electrode. We have found that optimum Nation requirement depends on the platinum loading and it increases with decrease in Pt loading. For electrodes with 0.5, 0.25 and 0.1 mg/cm(2) Pt loading, best performance was obtained at about 20, 40 and 50% Nation ionomer loading, respectively. (C) 2004 Elsevier Ltd. All rights reserved.