Solvate formation is a common occurrence among organic, organometallic, and inorganic compounds. Its impact on the stability and bioavailability of pharmaceuticals has led to considerable investigation of solvated drug substances. Some compounds display indiscriminate solvate formation, while others are considerably more selective. Significantly, the structural features that lead to one behavior or another have not been identified. Hence, empirical approaches are required for the discovery of solvates. Two situations can readily be envisaged that would tend to favor solvate formation. First, compounds in which potential intermolecular interactions, such as hydrogen bonding, are not well satisfied in the unsolvated form generally incorporate solvent molecules to provide strong intermolecular interactions and often solvate selectively based on functionality. The other limiting case is solvent inclusion to decrease void space in the crystal. Most compounds have contributions from both of these driving forces, which can be viewed as lowering the crystal free energy primarily through electrostatic and van der Waals interactions, respectively. Readily solvated pharmaceuticals have received attention in the literature, two prominent examples are sulfathiazole and gossypol. Sulfathiazole is an antibacterial sulfa-drug known to crystallize in over 100 solvates/cocrystals and five solvent-free polymorphs. It forms solvates with many solvents; however, there are some notable exceptions, which include hydrocarbon and halogenated solvents. Solvated sulfathiazole forms a diverse set of crystal structures, as well as several isostructural solvates. In some cases, the role of the solvent is to fill void space in the lattice (e.g., acetonitrile, dioxane), while in other crystals the solvent satisfies specific intermolecular interactions (e.g., N-formyl piperidine). Gossypol is a natural product that has been used as a male contraceptive and it forms solvates/cocrystals with nearly 100 molecules. Solvates can be generated from nearly every common organic solvent. It does, however, crystallize in a solvent-free form from ligroin and mixtures of hexane and diethyl ether. Like sulfathiazole, gossypol forms isostructural solvates, in which the solvent fills a cavity in the structure (e.g., carbon tetrachloride,m-xylene), as well as solvates with specific hydrogen-bonding interactions between gossypol and the included solvent (e.g., acetic acid, 2-propanol).