Polysulphurized olefin compositions used as additives for gear oils, cutting oils, and as sulphurizing agents in organic media are obtained by a process comprising:a stage (1) in which at least one compound chosen from among sulphur dichloride and monochloride is reacted with at least one aliphatic monpolefin with 2 to 12 carbon atoms, thus forming an adduct;a stage (2) in which sulphurized hydrogen and at least one mercaptan is reacted with ammonium or alkali metal hydroxide dissolved in at least one aliphatic monoalcohol with 1 to 4 carbon atoms, which is substantially anhydrous, so as to give an alcoholic solution;a stage (3) in which contacting takes place between the adduct obtained in stage (1) and the alcoholic solution obtained in stage (2);a stage (4), in which the resulting mixture is heated and then the aliphatic monoalcohol is eliminated by distillation, while adding water in a quantity adequate for maintaining in solution the reagents and the mineral products formed during the reaction; anda stage (5) in which elimination takes place of the aqueous phase and recovery takes place of the organic phase mainly constituted by the polysulphurized olefin composition.