The determination of the current distribution in a polymer electrolyte fuel cell (PEFC) is of great practical importance to optimize the process parameter such as the flow field design, the humidification of reaction gases and the utilization of the fuel gas. In this paper, subcells approach is used to measure current density distribution in PEFC with an active electrode area of 30 cm(2). Fuel cell performances determined under different operation conditions clearly indicate that the water balance influences the cell performance most significantly. Furthermore, it is interesting to note that under certain condition both membrane drying and electrode flooding are shown simultaneously inducing performance decaying. (c) 2004 Elsevier B.V. All rights reserved.