Compression-induced phase transformations in pharmaceutically-relevant organic materials is an area of current interest due to the increasing number of compounds that undergo such changes in pressure ranges relevant to pharmaceutical manufacturing processes. These changes have a material impact on the functionality of the compounds giving rise to potential changes in, for example, mechanical properties and solubility. Changes to the solid-form have also been observed at pressures relevant to tableting, including polymorphic transformations (e.g. chlorpropamide ), partial amorphisation (e.g. theophylline, nitrofurantoin, amlodipine besylate ), and crystallization of amorphous drugs (e.g. indomethacin, sucrose, celecoxib ), using a range of characterization techniques including differential scanning calorimetry (DSC), spectroscopy and X-ray and neutron diffraction. Investigations of pure substances have shown that the thermodynamic stability of polymorphs can change as a function of pressure but, in addition, the type of pressure (isotropic vs anisotropic) is important and can promote or inhibit transformation e.g. ammonium nitrate. These changes have been observed not only for pure components but also within formulated tablets composed of drug-excipient mixtures to create robust compacts that mimic oral solid dosage forms for delivery to patients.