The use of both differential scanning calorimetry and thermogravimetry to study the solid state dehydration of hydrated pharmaceutical compounds, and the subsequent behavior of the anhydrous drug is discussed. Three compounds, each with differing thermal behavior serve as examples. Emphasis is placed on applying current solid state reaction kinetics theory to analyze non-isothermal data and ascribe possible mechanisms for the various physicochemical transformations and physical transitions monitored. Solvent removal from a final product can effect partial or total dehydration. It is necessary to ascertain the dehydration temperature limits, and, of equal importance to examine the ability of the compound to rehydrate. The dehydration/rehydration behavior of a drug candidate is described as a practical demonstration of the utility of thermal analysis in pharmaceutical process development.