Polymorphs and pseudopolymorphs of pharmaceutical drugs frequently exhibit different physicochemical properties such as bioavailability, comminution, and shelf-life. Control of polymorphism is therefore critical to pharmaceutical formulation and distribution. In this talk we will present the effect of hydrogen bonding and other properties of thiol and silane self-assembled monolayers in the crystal growth of polymorphs and pseudopolymorphs of drugs such as carbamazepine, theophylline and indomethacin.