Life-cycle assessment is a useful instrument to evaluate the ecological performance of innovative energy systems. This paper investigates the production process of polymer electrolyte fuel cell (PEFC) stacks, identifies the ecological contributions of various components and materials and compares the results with impacts due to utilization of the stacks in a vehicle (i.e. hydrogen or methanol production and direct emissions). The production of fuel cell stacks leads to environmental impacts which cannot be neglected compared to the utilization of the stacks in a vehicle (the actual driving process). These impacts are mainly caused by the platinum group metals for the catalyst and, to a lesser degree, the materials and energy for the flow field plates. The paper identifies several options how to further enhance the environmental advantages of fuel cells. (C) 2000 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.