[en] The role of resonance interaction in the energy transfer observed in the concentrational single crystal series CaF₂-Ho³⁺, Eu²⁺ has been determined by means of investigation, using the phase method, of luminescence decay kinetics of europium in specimens with the constant content of europium (0.08 mol.%) and variable content of holmium at 300 and 77 K. In the single crystals under study, a monotonous decrease of europium, tau, has been observed, which shows that the energy transfer from Eu²⁺ to Ho³⁺ occurs during the lifetime of the europiu excited state