The generalized experimental results of delta electron yield obtained at the NSC KIPT electron accelerators in the energy range from 0.5 MeV to 1.6 GeV are presented. Thin foils of Be, Al, Si, Ni, and Nb were used as experimental targets. It was established in general that delta electron yield is roportional to the product √T∙Z/A, where T is the thickness of the sample in g/cm2 and it has a linear dependence. It is shown that the main factor of delta elec-
tron yield increasing is not primary beam energy, but the electron density of the experimental target