Methanol crossover from the anode to the cathode through the polymer electrolyte membrane (PEM) has been one of the detrimental factors affecting the performance of direct methanol fuel cells (DMFCs). Extensive research work has been in progress for developing CH3OH crossover tolerant electrolyte membranes. The need for assessing CH3OH crossover by an easier and faster method than the conventional CO2 analysis method has become significant. For this, a potentiometric method has been developed and tested using the Nation membrane. By recording the potential (E) of a PtRu/C electrode in 0.2 M H2SO4 supporting electrolyte during CH3OH crossover, it has been shown that the slope (dE/dt), of E versus t (time) curve, is proportional to the crossover rate. From the time required to reach the equilibrium concentration of CH3OH on either side of the polymer electrolyte membrane, CH3OH crossover rate has been calculated. This method is expected to be useful in studying polymer electrolyte membranes and also in industry as a quality control technique. The method can also be used to sense methanol concentration. (C) 2003 Elsevier Science B.V. All rights reserved.