This work illustrates the application to direct methanol fuel cell technology of an innovative reference electrode setup with a through-plate configuration, which enables localised measurement of electrode potential in an operating cell. The utility of the technique is demonstrated by monitoring the evolution of anode overpotential at two different locations in the cell over different time scales, ranging from minutes to hundreds of hours. The measurements provide valuable insight into critical degradation phenomena, identifying localised hydrogen evolution on the anode during short term operation and highlighting the contribution of anode temporary degradation to the overall performance decay during long term operation. This novel approach can be used as a diagnostic tool to improve operational protocols, such as refresh cycles, for direct methanol fuel cells. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.