In a previous investigation, we observed that in the presence of a conventional vulcanization system, the addition of white rice husk ash (WRHA) to natural rubber (NR) compounds increased the rate of crosslinking and lowered the apparent activation energy (E-a] of the vulcanization reaction more strongly than the other fillers used. In this work, commercial fillers, such as precipitated silica (Zeosil-175) and carbon black (N762), were partially replaced by black rice husk ash and WRHA. Cure studied were carried out on a TI-100 curometer at 150, 160, 170, and 180degreesC, and the overall rates and the E.'s for the vulcanization process were calculated for each compound, with the assumption that vulcanization followed first-order kinetics. Again, WRHA showed some catalytic effect on the NR vulcanization.