The contact resistance between the gas diffusion layer (GDL) and the bipolar plate has been experimentally estimated as they are assembled in proton exchange membrane (PEM) fuel cells. A number of coated and non-coated GDLs, graphite bipolar plates and a sealing gasket were employed to perform the test. The results show that the contact resistance of the non-coated GDLs (or carbon substrates) is highly influenced by the competing effects of the initial thickness of the GDL and the polytetrafluoroethylene (PTFE) loading. As for the coated GDLs, the PTFE loading present in the microporous layer (MPL) was found to play a positive role in establishing a good contact between the GDL and the bipolar plate. (C) 2012 Elsevier Ltd. All rights reserved.