In rice-producing countries, large amounts of rice husks are generated as waste material for which there is no ready use and in some cases may have a negative value because of the cost of disposal. Most of these countries depend on fossil fuels for their energy uses, and rice husk can be used to supplement such energy sources using thermochemical conversion processes. However efficient operation of thermochemical conversion systems requires a thorough understanding of the influence of the influence of the composition and thermal properties of rice husks on their behavior during the conversion process. In this study, the thermal behavior of four rice husk varieties (Lemont, ROK14, CP 4, and Pa Potho) was examined at three heating rates (Ia, 20, and 50 degrees C / min) in stationary air atmosphere. The thermal degradation rate in active and passive pyrolysis zones, the initial degradation temperature, and the residual weight at 600 degrees C were determined. increasing the heating rate increased both the thermal degradation rate and the residual weight and decreased the initial degradation temperature. The higher :he cellulosic content of the rice husk, the higher the thermal degradation rate and the initial degradation temperature. Also, higher ash content in the lice husk resulted in higher residual weight at 600 degrees C.