Recent advances in the design and construction of a hydrogen/oxygen PEM fuel cell stack are presented. A test bench including measurement and control devices to monitor the fuel cell operating parameters was mounted. The influence of the characteristics of the membrane electrode assembly, bipolar plates, etc., on the performance of the fuel cell stack was studied. The behavior of the fuel cell stack with a different number of cells in series was evaluated. in order to identify and minimize the energy losses a critical analysis of the results was done. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.