By using a semi-efficient vulcanisation system, two grades of epoxidised natural rubbers (ENR 25 and ENR 50) were incorporated separately into calcium carbonate (CaCO3 ) filled natural rubber (NR) compounds at 5.0, 10.0, 15.0, 20.0 and 25.0 phr. An investigation was carried out to examine the effects of the ENRs on cure characteristics, rubber - filler interaction and crosslink density of the CaCO3 filled NR compounds. Results revealed that both ENR 25 and ENR 50 functioned as curatives and compatibilizers. They decreased the scorch time, cure time and minimum torque; increased torque difference, crosslink density and degree of rubber - filler interaction. The higher the ENRs loadings; the lower were the scorch and cure times and the higher were the torque difference, crosslink density and degree of rubber - filler interaction. At a similar loading, ENR 50 exhibited a more pronounced curative and compatibilization effects than ENR 25.