Transference number measurements were determined by a direct method for LiClO4 solutions in propylene carbonate and acetonitrile at 25 degreesC. A comparison is reported between theoretical calculations of transference numbers using a model based on the Lee-Wheaton theory with values of conductometric parameters, and thermodynamic ion pairing constants determined from previously reported conductivity data. (C) 2004 Elsevier B.V. All rights reserved.