Activity coefficients at infinite dilution gamma(infinity)(i) of 17 alkanes, alkenes, and alkyl benzenes in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate were determined by gas chromatography using the ionic liquid as the stationary phase. The measurements were carried out at different temperatures between 303.15 K and 343.15 K. From the temperature dependence of the limiting activity coefficients, partial molar excess enthalpies at infinite dilution H-i(E,infinity) of the organic solutes in the ionic liquids have been derived.