PROJECT SUMMARY Data sharing is essential to promote equity and maximize the impact of the significant investment in the BRAIN Initiative. Data sharing plans are now required for BRAIN Initiative funding, but there is an urgent need to de- velop specific policies and practice guidelines that address ethical challenges and stakeholder concerns. Data sharing has been the object of study in other fields, such as genomics, but there are distinctive features of the BRAIN Initiative that are likely to present unique challenges and raise new concerns. Our own experience and research with investigators conducting BRAIN Initiative-funded studies of closed loop or adaptive deep brain stimulation suggests that the practice of sharing data is inconsistent and incomplete, despite broad agreement that it is important. Investigators raised ethical challenges with sharing human brain data, including issues re- lated to privacy, consent, interoperability, and competing commercial and professional interests. The objective of this proposal is to engage key stakeholders in a deliberative process to identify challenges and concerns specific to sharing human data from BRAIN Initiative studies and generate empirically informed policy and practice options to facilitate responsible sharing of human data within the BRAIN Initiative. In Aim 1, we will use informational interviews and document analysis to identify BRAIN Initiative-specific data sharing challenges, as well as relevant policy and practice considerations. In Aim 2, we will use semi-structured interviews and sur- veys to evaluate BRAIN Initiative research participants’ attitudes, preferences, and concerns about data shar- ing and brain privacy. In Aim 3, we will employ a modified policy Delphi process with diverse stakeholders to prioritize challenges and generate and evaluate policy and practice options that address high-priority chal- lenges. This contribution will be significant because it will provide critical empirical data to inform practice guidelines and future policy development. By engaging diverse stakeholders, this project will help instill trust, avoid inequities, and ensure success of current and future data sharing efforts within the BRAIN Initiative. This project is innovative in its engagement with multiple diverse stakeholder groups and its use of mixed methods incorporated into a modified policy Delphi framework. The work is feasible in our hands as demonstrated by the productivity of this team in prior work, as well as our collective data sharing and neuroethics expertise, and experience with empirical social science methods.