The infinite dilution activity coefficients for benzene, toluene, ethylbenzene, n-heptane, n-octane, n-nonane, and n-decane in triethylene glycol and tetraethylene glycol were experimentally measured by gas chromatography at (50 to 130) degreesC. The experimental data were correlated with the modified UNIFAC (Dortmund) method, and the group interaction parameters were obtained. The experimental data were compared with the calculated results, and a good agreement between experimental data and calculated values was obtained.