Project Summary: Developing a Robust Strategy for Living Donor Follow-up and Engagement There are more than 150,00 living kidney donors in the US, and the number of new donors is increasing yearly. Understanding the risks and sequelae of donation is a practical requirement for expanding live donor kidney transplantation and an ethical requirement for supporting informed consent and honoring an altruistic act. This requires the collection of granular follow-up data in donors, and a comparison to healthy non-donors. To date, national efforts at kidney donor follow-up and long-term engagement have failed. As a living kidney donor myself, I am intimately aware of the profound and systemic failures in post-donation surveillance from both the donor-level and the health system-level. In 2013 a national policy mandating transplant centers meet standards for living donor follow-up was implemented, yet this policy has proven nearly impossible for transplant centers, with fewer than 50% successful in meeting the mandate. Continued engagement with transplant centers not only allows a better scientific understanding of the implications of donation, but also allows careful surveillance of donors to identify early physiologic changes (such as hypertension) and intervene before these become major adverse outcomes. Furthermore, a proper healthy non-donor cohort has never been successfully captured and studied. To improve this ongoing failure, in 2017 we launched a pilot Living Donor Collective (LDC) at 10 kidney transplant centers, centralized though the Scientific Registry of Transplant Recipients (SRTR). In an effort to improve living donor follow-up in a systematic, scientific manner that can be disseminated to centers across the country, we will take the important first steps of evaluating how the 10 pilot transplant centers and the SRTR implemented the LDC and use this information to plan the next iteration of this important endeavor. Since only 10 centers participated in the pilot, out of 273 transplant centers in the US, it is critical to understand barriers to implementation across a wide spectrum of transplant center characteristics. Guided by an implementation science framework and a mixed methods approach, we aim: (1) to understand LDC implementation among pilot centers and SRTR, (2) conduct a formative evaluation and assess transplant center readiness and capacity for participation in the LDC across the US, and (3) create an implementation strategy to refine and expand the LDC. This study will provide a comprehensive understanding of implementation challenges, successes, and failures of a centralized program for living donor follow-up. This provides the foundation for all U.S. transplant centers to participate, solves a historically unsolvable and embarrassing health system challenge, and is necessary to prepare a future R01 to develop and implement centralized living donor follow-up nationally.