Activity coefficients at infinite dilution gamma(infinity)(i) have been measured for 17 organic solutes-alkanes, alkenes, and alkyl benzenes-in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][CF3SO3]) by the gas-liquid chromatographic method with the ionic liquid as the stationary phase. The measurements were carried out from (303.15 to 363.15) K. The partial molar excess enthalpies at infinite dilution H-i(E,infinity) of the solutes in the ionic liquid were also derived from the temperature dependence of the gamma(infinity)(i) values.