The general objective of the work was to adapt the existing technology of polymer electrolyte fuel cells (PEFC) to the demands for commercial applications and to make it competitive with respect to performance and costs compared to the present day technology of combustion engines. This should be realised by the use of optimised electrodes which enable a highly efficient operation with air at low overpressure and a simplified construction of the electrochemical cell which is capable of mass production and low-cost. The initial project cost goal (materials and fabrication, extrapolated to a production of 100,000 fuel cell systems per year) was 100-200 ECU/kW. The feasibility of this goal was planned to be ascertained by the development of a PEFC stack in the size of 3.5 kW rated power.