The effect of different accelerator/sulfur systems on the vulcanization behavior of highly filled EPDM compounds was studied. Cure kinetics were studied using Moving Die Rheometer (MDR); Chemical and physical crosslink densities were estimated by swelling measurements and by thermomechanical analysis (TMA). In order to evaluate the rate constant of the curing reaction, Coran＇s model was used. The activation energy of crosslinking for 4 systems varies between 71 and 103 kJ/mol. MDR results are in line with crosslink density data. The lowest tan delta in a semi-efficient system occurs with the highest crosslink density which is in good agreement with swelling and TMA results.