The presentation will focus on physicochemical characterization of pharmaceutical solvates and their application in drug development. Case studies from Merck will be presented: (a) a solvate of an active pharmaceutical ingredient (API) was selected for further development; (b) a solvate was used to obtain a highly crystalline API hydrate; (c) a solvate was applied in process optimization to reject an impurity and improve product yield. Emphasis will be placed on how a good understanding of the characteristics of pharmaceutical solvates leads to successful applications of the solvates in drug development.