A study has been made of the distribution of diphenylsulphide, diphenylsulphoxide, thiophene and dibenzothiophene in extraction systems consisting of octane and polar organic solvents and octane and water-organic mixtures. The relationships governing the distribution of diphenylsulphide and diphenylsulphoxide are explained on the basis of the principle of additivity of the free energy of distribution. It is shown that the replacement of aliphatic substituents with aromatic substituents reduces the capacity of the sulphide group and, especially, the sulphoxide group to be solvated by the polar phase, The similarity in the nature of change in the distribution constants of thiophene and dibenzothiophene on the one hand and aromatic hydrocarbons on the other as a function of the nature and composition of the polar phase has been established.