Vapor-liquid equilibria (VLE) of binary mixtures containing the high boiling solutes: nonan-1-al, 4-methyl-benzaldehyde, nonan-2-one, and 4-phenylbutan-2-one and the ionic liquid (IL) [EMIM] [NTf2] were studied by using the transpiration method. VLE measurements were carried out over the whole concentration range at different temperatures between 298 and 323 K. Activity coefficients gamma(i) of these solvents in the ionic liquid have been determined from these data using the NRTL-equation. In addition vapor pressures of the pure solutes 4-methyl-benzaldehyde, nonan-2-one and 4-phenylbutan-2-one have been measured as function of temperature and their enthalpies of vaporization have been obtained. (C) 2004 Elsevier B.V. All rights reserved.