The Scatchard-Hildebrand theory of regular solutions was modified by introducing the excess entropy of mixing term and by using temperature dependent solubility parameters. A comparison was made of the present treatment with the data available in the literature and the experimental results concerning the n-hexane-benzene-toluene and n-hexane-benzene-monochlorobenzene systems. The modified theory was shown, from the knowledge of pure components only, to be capable of predicting vapor -liquid equilibria for systems not containing polar components and useful for screening solvents effective for extractive distillation.