In this work we report the synthesis and the characterization of poly(vinyl alcohol) (PVA)-based proton-conducting membranes. In particular, we describe a cross-linking process of PVA with glutaraldehyde, which gives rise to membranes with enhanced morphological, thermal, and electrochemical characteristics. The critical role of the dispersion of a SiO2-based ceramic filler in promoting liquid retention and in enhancing the proton conductivity of composite PVA-based membranes is also discussed. (c) 2005 The Electrochemical Society.