In this work, the permeability of carbon dioxide through Nafion (R) EW 1100 has been studied at different temperatures, ranging from 30 to 80 degrees C. Three conditions were tested: water soaked, water vapour equilibrated and completely dry. When water is present, carbon dioxide permeability of the membrane shows a volcano shape with a maximum of 2.69* 10(-11) [cm(3) (STP) cm cm(-2) s(-1) Pa-1] at around 50 degrees C. In dry condition, the permeability unilaterally increases from 2.63*10(-13) to 8.41*10(-13) [cm(3) (STP) cm cm(-2) s(-1) Pa-1]. In hydrated Nafion, the hydrophilic domain is interpreted as the major transport channel for carbon dioxide, and reduced solubility of carbon dioxide at elevated temperature is the main cause for the decline of gas permeation. Carbon dioxide permeation enhancement by methanol dissolved in Nafion is negligible in a normal operating direct methanol fuel cell. (C) 2007 Elsevier B.V. All rights reserved.