For a fuel cell system using pure hydrogen as fuel, high hydrogen utilization operation is required because the exhausted hydrogen from the fuel cell is not used as a heat source for a reformer. While the hydrogen utilization is very high, any minor imbalance in the distributed flow causes a shortage of hydrogen gas. In order to achieve high hydrogen utilization operation, cells humidified at the cathode side, of counter flow type and with two-block divided stack where the hydrogen gas is fed to the first block with its exhaust hydrogen being fed to the second block have been developed. Five kilowatts class (100 cells) short stack systems fabricated to above specification showed stable operation at hydrogen utilizations up to 96%. Crown Copyright (C) 2008 Published by Elsevier Ltd on behalf of International Association for Hydrogen Energy. All rights reserved.