A new type of reinforced composite perfluorinated polymer electrolyte membrane, GORE-SELECT™ (W. L. Gore & Assoc.), is characterized and tested for fuel cell applications. Very thin membranes (5–20 (μthick) are available. The combination of reinforcement and thinness provides high membrane conductances (80 S/cm2 for a 12 μm thick membrane at 25°C) and improved water distribution in the operating fuel cell without sacrificing longevity or durability. In contrast to non-reinforced perfluorinated membranes, the x-y dimensions of the GORE-SELECT membranes are relatively unaffected by the hydration state. This feature may be important from the viewpoints of membrane/electrode interface stability and fuel cell manufacturability.