It is known that trace amounts of cations have a detrimental effect on the liquid-phase conductivity of perfluorosulfonated membranes at room temperature. However, the conditions used were very different from typical fuel cell conditions. Recent research has shown the impact of conductivity measurement conditions on NH4+ contaminated membranes. In this study, the impact of nonproton-containing cations (Mn+ = Na+,Ca2+, and Fe3+) on Nation membrane (N-211) conductivity was investigated both in deionized (DI) water at room temperature (similar to 25 degrees C) and in the gas phase at 80 degrees C under conditions similar to in a PEMFC. These conductivities were compared with those of Nation membranes contaminated with NH4+ ions. Under the same conditions, the conductivity of a metal cationic-contaminated membrane having the same proton composition (y(H+m)) was similar, but slightly lower than that of an NH4+-contaminated membrane. The conductivity in the purely H+-form of N-211 was more than 12 times greater than the Mn+-form form at 25 C in DI water. At 80 C. the gas-phase conductivity was 6 times and 125 times greater at 100%RH and 30%RH. respectively. The quantitative results for conductivity and activation energy of contaminated membranes under typical fuel cell conditions are reported here for the first time. (C) 2010 Elsevier B.V. All rights reserved.