Activity coefficients at infinite dilution gamma(i)(infinity) of alkanes, alkenes, and alkylbenzenes as well as of the linear and branched C-1-C-6 alcohols, acetone, acetonitrile, ethyl acetate, alkyl ethers, and chloromethanes in the ionic liquids 1-methyl-3-ethyl-imidazolium bis(trifluoromethyl-sulfonyl) amide and 1,2-dimethyl-3-ethyl-imidazolium bis(trifluoromethyl-sulfonyl) amide were determined by gas chromatography using the ionic liquids as the stationary phase. The measurements were carried out at different temperatures between 313 K and 363 K. From the temperature dependence of the limiting activity coefficients partial molar excess enthalpies at infinite dilution H-i(E,infinity) of the solutes in the ionic liquids have been derived.