A major improvement in the performance of a direct methanol fuel cell (DMFC) can be expected with a decrease of methanol crossover from the anode to the cathode of the cell. The focus of this paper is on investigation of methanol permeability when the membrane is processed at a high temperature. This investigation takes into consideration the conductivity of the membrane and the methanol permeability is Studied as a function of processing temperature for the membrane. Reduced methanol permeability is observed when the membranes are processed at temperatures much above the glass transition temperature but below the degradation temperature of the membranes. The permeability of methanol decreased irrespective of the thickness of the membrane on processing. (C) 2007 Elsevier B.V. All rights reserved.