The determination of hydrogen permeation through a polymer electrolyte membrane is often achieved through electrochemical methods, under the assumption of no oxygen at the working electrode. However, multiple experiments utilizing low hydrogen crossover conditions have shown reduction currents resulting from trace amounts (2-3 ppm) of oxygen. For conventional membranes, hydrogen crossover is sufficient to overwhelm the trace oxygen, such that the hydrogen permeation results are unaffected. For those conditions with low hydrogen crossover, the presence of trace oxygen can become dominant. This is particularly relevant for advanced polymer electrolyte membranes with very low gas permeability. The use of electrochemical techniques to ascertain the hydrogen permeation coefficient for membranes with low gas permeability was found to be significantly influenced by the presence of trace oxygen. (C) 2012 Elsevier B.V. All rights reserved.