A study has been made of the composition and structure of organosulphur compounds of 50 degree 400-540 degrees C distillates of Orenburg crude oil. The organosulphur compounds are mainly benzo- and dibenzothiophene derivatives with a degree of hydrogen non-saturation of up to 22 and 34 respectively and with saturated cyclic sulphides, The quantitative distribution of the homologous groups of compounds that are present has been established, and their cyclicity and degree of substitution and the length and structure of the radicals have been assessed.