A commercial Nafion 112 membrane loaded with the catalysts and catalysts' support in a segmented way was used for a H-2/air PEM fuel cell. On this membrane, the anodic and cathodic catalysts with their support were loaded on five consecutive places in a back to back style forming five catalyst islands of same dimensions on each side of the membrane. So, five sub-fuel cells were existed in one fuel cell compartment. These subeells are connected ionically but not electronically. The polarization behavior for these subcells was measured separately when the other subcells were at a zero load and simultaneously when they were polarized at the same load. Also, the temperature gradient within this segmented PEM fuel cell was measured in front of cathode side of the sub-fuel cells when hydrogen and air gases were flown in a parallel or opposite direction to each other. Temperature gradients were correlated with the observed performance of the fuel cell. (C) 2007 Elsevier B.V. All rights reserved.