Results of investigations on possible applications of the EPR method for studying of steelwork slags properties and sintering processes involving some slag components are presented. Comparative experimental studies have been carried out at X-band (9.4 GHz) both with industrial slags and synthetic slag-like systems obtained by sintering mixtures of pure reagents of the Ca-Al₂O₃ - Fe₂O₃ phase diagram. Tests on evolutions of EPR spectra during sintering processes have also been done, including sintering raw mixtures currently used in cement industry. EPR spectra of Mn²⁺ ions, which have been observed quite resolved in nearly all studied samples, have been established very useful for studying kinetics of sintering processes in systems involving the slags and components of the CaO - Al₂O₃-SiO₂ diagram.