In the countries of the former U.S.S.R. the composite sorbent 'Anfezh' (ferric-potassium hexacyanoferrate on a cellulose carrier) is used for the determination of caesium radionuclides in aqueous media. The certified efficiency of Anfezh for radiocaesium extraction is 98+/-1%. Anfezh is cheap, does not require long preparation before use and permits rapid pre-concentration of radiocaesium. Copyright (C) 1996 Elsevier Science Ltd.