In this study, diffusion coefficients of alkylimidazolium tetrafluoroborates and hexafluorophosphates ionic liquids in water at room temperature were measured by the Taylor dispersion experiment. The Wilke-Chang equation underestimated the diffusion coefficient, but a modified Wilke-Chang equation correlated diffusion coefficients well with molar volumes. The conductivities of these ion liquids were also measured. Infinite dilute conductances were calculated. The Nernst-Haskell equation accurately estimated diffusion coefficients using the infinite dilute conductance obtained. (c) 2007 Elsevier B.V. All rights reserved.