[en] The extraction of Pu(VI) and Pu(III) from sulphuric acid by TOA in toluene has been studied as a function of the acid and tri-octyl amine concentration. A comparison of the extraction properties of Pu with those of U(VI) and U(IV) has been made. It was found that the extraction properties of Pu(VI) are very similar to those of U(VI) and that TOA is a relatively poor extractant for Pu(III). U(VI) shows better extraction properties than Pu(III). The results obtained are considered in the stabilities of the complexes formed by these elements in the organic and aqueous phase. A method of separation of both elements by solvent extraction based on changing their oxidation states is suggested. The results prove that TOA may be used successfully in the extraction of Pu(VI) alone or together with U(VI) from sulphuric acid in order to separate them from some other metal ions in oxidation states 3+ or lower. The separation of both elements from each other can easily be performed by an addition of uranium(IV) sulphate by which the Pu is reduced to Pu(III) and stripped into the aqueous phase. (T.G.)