This paper reviews the results obtained by studying the dual-temperature ion-exchange fractionation (DTIXF) technique. The DTIXF is based on the use of different affinity at different temperatures of ion exchangers towards ions to be separated. This technique allows to design absolutely reagentless and, as a result, wasteless fractionation technology. The review considers the temperature dependencies of selectivity of commercially available ion-exchange (IX) resins towards components of ionic mixtures of different complexity starting from binary model systems up to naturally existing nonacomponent effluents. A novel approach for predicting the temperature sensitivity of a given IX system is presented and discussed. The same approach has been shown to be applicable for the design of IX resins with temperature-dependent selectivity. The paper also reports the results obtained in the practical application of DTIXF technique for concentration of magnesium from seawater and copper from acidic mine waters. The flowsheets of DTIXF processes are proposed and discussed.