This book reports on the preparation and characterization of solution-cast composite membranes and nanofiber reinforced membranes obtained by electrospining technique. It describes cutting-edge analysis techniques that suggest that the reinforced fibers enhance the mechanical properties and produce a remarkable reduction of the methanol permeability. Coverage includes the performance of fuel cells containing different membrane-electrode assemblies (MEAs) for PEMFC application, as well as the analysis of the methanol permeability in composite materials for direct methanol fuel cell (DMFC) applications.