The direct methanol fuel cell (DMFC) has the potential to replace battery technology for micro & small portable applications and may be used in larger applications if key technological barriers can be overcome. Presently, fuel crossover through the electrolyte is a major limitation on the performance and fuel utilization efficiency. Different approaches to reduce crossover have been examined, including new membranes, membrane modification, variation of operating conditions, and novel electrode design. The investigation of methanol crossover through fuel modification represents an important new approach to the reduction of crossover in a DMFC. In this study, systems of acetic acid/water/methanol & propionoic acid/water/methanol have been found to reduce methanol crossover through Nafion® 117 membranes, carbon fibre diffusion layers, diffusion electrodes and membrane electrode assemblies.