Surface tensions were measured for the ten binary liquid systems: cyclopentane + carbon tetrachloride, cyclopentane + tetrachloroethylene, cyclopentane + benzene, cyclopentane + toluene, cyclohexane + tetrachloroethylene, cyclohexane + benzene, cyclohexane + toluene, cyclohexane + cis-decalin, cyclohexane + trans-decalin, and benzene + o-xylene. The system cyclohexane + benzene was studied at 20 and 30 °C. Measurements for the other nine systems were carried out at 25 °C. The principle of corresponding states was used to correlate the surface tension results with other properties of the pure component liquids and of their binary mixtures.