A new and rapid method has been developed for the quantitative extraction of Ru/III/ with 1,2,3-benzotriazole /1,2,3-BT/ into 1-pentanol. The extraction coefficient value of Ru/III/ between 1-pentanol and an aqueous 5% solution of 1,2,3-BT in 2M sodium acetate-acetic acid buffer showed a maximum value of E=46 at pH 4.5. The effect of various other parameters on the extraction coefficient of Ru/III/ such as solvents, anions, cations, etc. have also been studied. The stoichiometry of metal:reagent determined by the method of substoichiometric extraction and slope ratio method was found to be 13. Decontamination factors for many elements in the substoichiometric extraction of Ru/III/ were also evaluated.