The thermophysical properties of 1-alkylpyridinium bis(trifluoromethylsulfonyl)imide, CnpyTf2N ionic liquids where n = 4, 8, 10, or 12 have been determined. Density �, and dynamic viscosity η, were determined at T = (293.15 to 353.15) K and refractive index nD, was measured at T = (293.15 to 333.15) K. Empirical correlations are proposed to represent the present experimental results. The values of the coefficient of thermal expansion were calculated from the experimental density values. The thermal decomposition temperature, Td was also determined using thermogravimetric analyzer (TGA) at a heating rate of (10 and 20) K · min-1. © 2009 Elsevier Ltd. All rights reserved.