[en] A rapid and simple method of selective concentration and separation of ¹³⁷Cs from a mixture of long-lived fission products using extraction chromatography was suggested. The polytrifluorochloroethylene KEL-F of 4x10^-5 m in diameter was used as a solid support for the dicarbolide-H⁺ or its chloroderivative in nitrobenzene within the concentration range from 0.22 to 0.3M. A simple radiometric technique can be used for the determination of ¹³⁷Cs. The new method can be recommended for the concentration of ¹³⁷Cs from large volumes of solutions of mineralizates of biological material. (author)