To maintain the efficiency of proton exchange membrane fuel cells (PEFCs) without flooding, it is necessary to control the liquid water transport in the gas diffusion layer (GDL). This experimental study investigates the effects of the GDL fiber direction on the cell performance using an anisotropic GDL The results of the experiments show that the efficiency of the cell is better when the fiber direction is perpendicular to the channel direction, and that the cells with perpendicular fibers are more tolerant to flooding than cells with fibers parallel to the channel direction. To determine the mechanism of the fiber direction effects, the liquid water behavior in the channels was observed through a glass window on the cathode side. The observations substantiate that the liquid water produced under the ribs is removed more smoothly with the perpendicular fiber direction. Additionally, the water inside the GDL was frozen to observe its distribution using a specially made cell broken into two pieces. The photographic results show that the amount of water under the ribs is larger than that under the channels using the parallel fiber direction GDL while the water distributions in these two places are almost equal level with the perpendicular fiber direction GDL This freezing method confirmed the better liquid water removal ability and better reactant gas transportation in the GDL with the fiber direction perpendicular to the channel direction. (C) 2010 Elsevier B.V. All rights reserved.