Pinholes in the membrane electrode assembly (MEA) of a fuel cell can lead to premature fuel cell failure. The main causes for pinhole formation are contaminant particles, non-uniform stress distribution, and membrane corrosion. In this paper fuel cell performance is compared before and after piercing the MEA with a pin to introduce a pinhole. Experiments revealed that under some operation conditions, the presence of a pinhole did not immediately impact performance. This implies that fuel cell engineers might overlook pinhole damage in its initial stages. However, durability testing shows that the performance of a fuel cell with a pinhole declines faster than that of a fuel cell with an intact MEA. During open circuit voltage measurement, a substantial voltage drop is observed for the fuel cell with a pinhole in the MEA. Simulation results point to the formation of a hot spot in the cathode catalyst layer of the fuel cell at the site of the pinhole. The temperature of the hotspot is 4 similar to 5 K higher than the surrounding area, which is not so high as to impair performance. This explains the steady operation of the fuel cell over a 40-hour run cycle. This study identifies increasing anode pressure as a method for pinhole detection in fuel cell stacks. Copyright (C) 2010 John Wiley & Sons, Ltd.