A series of composite membranes based on zeolite A and Nafion 117 have been fabricated for direct methanol fuel cells. The external surface of zeolite A has been modified to enhance the interface bonding between inorganic zeolite crystals and Nafion ionomer. The modified zeolite samples have been characterised using a combination of thermal analysis and spectroscopic techniques. Methanol permeability of Nation 117 could be reduced by as much as 86% by incorporating functionalised zeolite NaA crystals into the membrane. The effect of different functionalisation level is discussed. (c) 2007 Elsevier B.V. All rights reserved.