The affinity series of rare earth element complexes with HEDTA at pH 7.5 for the strongly basic anion-exchanger was determined. Based on the determined affinity series separation of Sm(III) - Ho(III) complexes with HEDTA in the macro-micro system at pH 4.0 and 7.5 on the strongly basic anion-exchangers Dowex 1x2, Dowex 1x4, Dowex 1x8 and Dowex MSA-1 (macroporous) in the HEDTA form was studied by frontal analysis. HEDTA as an eluent is completely useless for separation of intermediate lanthanides (Sm(III)-Ho(III)) on the cation-exchangers but it is effective for separation of some pairs of elements in the anion-exchange process.