Phantom Limb Pain (PLP) is a form of unpredictable neuropathic pain in Veterans with amputation. Current non-medication treatments for PLP are limited and more interventions are needed that take into consideration the unique needs of the Veteran population. PLP significantly impairs rehabilitation outcomes and community participation. One non-medication intervention is graded motor imagery (GMI). GMI consists of sequentially progressing from limb laterality training, to motor imagery, and then mirror therapy (i.e., observing movement using the visual illusion of an intact limb in a mirror). Although clinicians report benefit from use of the technique, barriers exist to supporting at-home use of the intervention. This VA Career Development Award-2 proposal focuses on refining a mobile app for GMI (VA-GMI) and then testing serial sessions of mobile app use in a sample of Veterans with lower limb amputation and moderate to severe PLP in their home setting. We have a current working prototype of the VA-GMI mobile app. The project will initially include serial cognitive interviews with 12 Veterans with lower limb amputation and PLP as they trial the VA-GMI mobile app. Following each interview, we will compile the themes and make iterative changes to improve the user interface and functionality of the mobile app. We will then invite the Veterans to try the new version over the course of a week and repeat the process. We anticipate that we can reach consensus on the improvements to VA-GMI mobile app within 2 major iterations. In years 2-5, we will conduct a pilot study to evaluate the feasibility and acceptability of the intervention with 36 Veterans with amputation and moderate to severe PLP. We will conduct this study virtually with all Veterans in their home environment. All Veterans will receive twelve intervention sessions. To allow for real-time observation and assistance with VA-GMI mobile app, we will use existing telehealth platforms to visualize and interact with the Veteran. The primary outcome measure is the Acceptability of Intervention Measure of the intervention sessions. We will measure process parameters (e.g., number of eligible participants, recruitment rate, retention rate). We will also objectively measure mobile app features (e.g., app usage, time spent on each screen view, user interaction with app user interface (i.e., button clicks and usage details)). We will explore the effect of VA-GMI mobile app on a number of domains hypothesized to be impacted by the intervention to aid in our responder analysis. Several measures will also be captured to characterize the population and inform outcome measurement selection for future studies. Outcome measures will be collected at baseline, post- intervention, 3-months, and 6-months from the baseline evaluation. This Career Development Award-2 work supports the development and training for Dr. Tonya Rich to become an independent VA researcher focused on the development and testing of novel r...