The ionic conductivity, sigma, of mixtures of poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfone) imide (LiTFSI) was measured as a function of molecular weight of the PEO chains, M. over the range 0.2-5000 kg/mol. Our data are consistent with an expression sigma=sigma(0) + K/M proposed by Shi and Vincent [Solid State Ionics 60 (1993)] where sigma(0) and K are exponential and linear functions of inverse temperature respectively. Explicit expressions for To and K are provided. (C) 2011 Elsevier B.V. All rights reserved.