The purpose of this Funding Opportunity Announcement (FOA) is to stimulate research in the area of organ and tissue donation among health disparity populations, such as racial and ethnic minorities, the socioeconomically disadvantaged, underserved rural populations, sexual and gender minorities, and other underserved communities. Proposed studies may include studying individual-level factors such as attitudes, beliefs, and behaviors towards organ and tissue donation, as well as the need for transplantation. In addition, studies may include examining the influence of social determinants of health on disparities in organ and tissue donation. Support will be provided for testing various hypotheses related to the barriers and challenges of organ and tissue donation, as well as for facilitating the development of novel interventions. Successful approaches should ultimately lead to an increase in the number of health disparity populations participating in living and deceased organ and/or tissue donation.