The problem of methanol crossover through a Nafion (R) membrane is one of the challenges in the application of direct methanol fuel cells (DMFCs). In order to reduce methanol crossover, a semi-interpenetrating polymer networks (IPNs) membrane composed of Nafion (R) and crosslinked DVB was prepared. This new membrane was found to be effective in reducing methanol permeation compared with unmodified Nafion (R) membrane. Although the conductivity and H-2/O-2 fuel cell performance were still lower than those of unmodified Nafion (R) membrane, the present results demonstrate the potential for using semi-IPN membranes as an electrolyte for DMFC. (c) 2006 Elsevier B.V. All rights reserved.