Black rice husk ash (BRHA) and white rice husk ash (WRHA) were incorporated into natural rubber (NR) using a laboratory-size two-roll mill. A conventional vulcanization system (CV) was chosen and cure studies were carried out on a TI-100 Curometer. The torque curves were obtained at 150, 160, 170, and 180degreesC. The overall rate and the apparent activation energy for the vulcanization process were calculated for each compound assuming that vulcanization follows first-order kinetics. For comparison purposes, two commercial fillers, precipitated silica (Zeosil-175) and carbon black (N762), were also used. It was observed that addition of WRHA to NR compounds increased the cross-linking rate and lowered the apparent activation energy more markedly than the other fillers.