The infinite-dilution activity coefficients of cyclohexane, cyclohexene, and benzene in four solvents, isophorone (CAS 78-59-1), dimethyl sulfoxide (CAS 67-68-5), dimethyl succinate (CAS 106-65-0), and propylene glycol (CAS 57-55-6), have been determined at temperatures ranging from 40 degreesC to 80 degreesC, by non-steady-state gas chromatography. These solvents are used commercially in the separation of mixtures of these hydrocarbons by extractive distillation so infinite-dilution selectivities have been calculated and studied in relation to this separation. The experimental activity coefficients were compared with those calculated by the UNIFAC method.