Rice husk, a renewable by-product of rice milling operations, is an energy source that can be utilized to meet the increasing demands for energy. Its utilization can also help rice millers meet increasing costs of rice husk disposal because of increasing restrictions on disposal. However industrial utilization of rice husk in thermochemical conversion systems to liberate energy requires the knowledge of its thermal characteristics for the proper design and modelling of these systems. The thermal degradation of four rice husk varieties (Lemont, ROK 14, CP 4, and Pa Potho) were investigated at three heating rates (10, 20 and 50 degrees C/min) in nitrogen atmosphere using the technique of thermogravimetric analysis between ambient temperature and 700 degrees C. The thermal degradation rate in active and passive pyrolysis zones, the initial degradation temperature, and the residual weight at 700 degrees C were determined. Increasing the heating rate increased both the thermal degradation rate and the residual weight at 700 degrees C, and decreased the initial degradation temperature. The higher the cellulosic content of the rice husk, the higher the thermal degradation rare and the initial degradation temperature. Also, higher ash content in the rice husk resulted in higher residual weight ait 700 degrees C. Rice husk could be degraded to the extent of 56-64%.