It was found from the fracture experiments that the fracture energy of the unfilled natural rubber did not vary significantly over a range of sample strain rate from 0.01 to 56 s-1, but there was significant variation in the fracture energy of the 25 phr carbon black filled natural rubber from 0.01 to 71 s-1 sample strain rate. The fracture energy of the 25 phr carbon black filled natural rubber at a sample strain rate of 0.1 s-1 was 25 kJ/m2, which was three times greater than it was at 10 s-1 sample strain rate. Furthermore, the carbon black fillers increased the fracture energy of natural rubber at quasi-static sample strain rates (0.01 – 0.1 s-1) by about 200%, but the carbon black fillers did not improve the fracture energy of natural rubber at sample strain rates between 5-29 s-1. In this strain rate range, the fracture energy of 25 phr carbon black-filled natural rubber was almost the same as that in the unfilled natural rubber. Above a sample strain rate of 30 s-1, the fracture energy was greater than the unfilled natural rubber. Finally, the crack speed did not vary significantly with loading rates for both unfilled and filled natural rubber.