XRD-CT has been successfully applied to a number of material science areas to elucidate the composition of batteries, catalysts, energy storage materials, and even biomineralization in human bone structures. These studies have not only provided details under ambient conditions but also during working processes. These studies provide spatially-resolved physico-chemical information from within the interiors of intact objects negating the need for any intrusive sample preparation. In contrast to conventional absorption contrast tomography which uses a full-field approach to provide information on density/absorption differences within a sample, XRD-CT uses a pencil-beam scanning approach to measure the average diffraction signal through the sample at a given point. With the rotation of the sample and reconstruction of the images from the data, a full crystallographic description of the sample that is spatially resolved can be provided. A recent review of pharmaceutical tablets using X-ray tomography highlighted the lack of investigations using XRD-CT into these systems. There is a significant challenge in this area due to the general low symmetry, large unit cell size, and poorer crystallinity often observed for softer organic materials. Here, we address this challenge and have applied XRD-CT to pharmaceutical tablets, which have been a significant omission as the field has developed. In particular, we explore the evolution of polymorphic forms in pharmaceutical tablets as a function of compaction pressure using glycolide as a pressure-sensitive marker. Glycolide undergoes a reconstructive phase transition at 150 MPa to a high-pressure polymorph (Form II) that is recoverable to ambient conditions which makes it an ideal pressure marker for our ex-situ measurements (Figure ). The pressure of this phase transformation is typical for an operating pressure in a tableting press used in the pharmaceutical industry. It should be noted that glycolide Form II has since been isolated at ambient pressure from cooling of a 2-propanol solution from 75°C to 35°C and is sufficiently stable to perform solubility measurements. Using XRD-CT we have been able to visualize the impact of compaction pressure on the contents of the tablet. These data indicate that the changes are far from uniform across the tablet. Serendipitously, we have been able to observe the chemical degradation and subsequent crystallization of the hydrolytic ring opening product of glycolide, 2-(2-hydroxyacetoxy)acetic acid, in-situ within a tablet on storage which has not been observed to date.