Dehydration-rehydration study of bauxite rock carries a great practical significance in preparing different alumina products, predicting the structure-property relationship of the high alumina bearing ore for its effective utilization and controlling the drying-firing schedule of bauxite based various alumina ceramics. This paper presents a comprehensive thermal dehydration-rehydration behaviour of the naturally occurring bauxite rock of India in powder form in relation to variation of temperature of thermal treatment and relative humidity of the environment.