Computational fluid dynamics (CFD) simulations were performed for four 10-cm(2) serpentine flow-fields with single channel, double channel, cyclic-single channel, and symmetric-single channel patterns to investigate the effect of flow-field design. High and low inlet humidity operating conditions were studied by calculating the distributions of overpotentials, current density distribution, and membrane water content at different cell voltages. At high inlet humidity, the double channel flow-field was predicted to have better polarization performance and uniform current density distribution, while at low inlet humidity there were little performance differences among four serpentine flow-fields. The current density profiles of cyclic-single channel and symmetric-single channel flow-fields were observed to have periodically similar plots and showed significantly low pressure drop. Considering low pressure drop of cyclic-single channel and symmetric-single channel flow-fields, these flow-fields would be advantageous for the larger scale system and low inlet humidity operation. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.