A primary goal of the current work was to examine the potential use of compaction energetics as a tool to predict particle deformation mechanism. Three deformation models, namely, those developed by Heckel, Walker, and Gurnham, were first used to evaluate the deformation mechanisms of 11 commonly used excipients. To complement the information gained from the deformation models, the mechanical energy used in tablet formation was then examined. It has been found that the sum of the work in the compression and decompression phases (plastic work) is a relatively good indicator of a material's plasticity. Conclusions based on this indicator regarding deformation mechanism for the different diluents used were in good agreement with those obtained from the different deformation models studied.