Viscosities of ionic liquids were correlated with two linear relations. The first one presents the temperature dependence of imidazolium-, pyridinium-, pyrrolidinium-, quaternary ammonium-, and nicotinium-based ionic liquids with high accuracy. The second one is a linear relation between logarithm of surface tension and fluidity involving the characteristic exponent phi, and fits the ionic liquids uniquely with phi = 0.30. Our previously measured surface tension data of ionic liquids and literature's were used in this study. The dependence of surface tension-fluidity relation of the imidazolium-based ionic liquids on the anion type is likely disappeared as alkyl chain length increases. (C) 2010 Elsevier B.V. All rights reserved.