An estimated 75%–90% of scientific experiments are not reproducible, resulting in $28 billion per year spent on irreproducible research in the United States alone. One promising solution to irreproducible clinical research is to publicly share trial data. However, journal editor and funding agency positions on data sharing, as well as the extent of reproducibility of trial results from shared data, are poorly understood. Absent this knowledge, progress toward more transparent and reproducible addiction science is likely to be thwarted. Our long-term goal is to improve the rigor of addiction research and the reproducibility of its results to ensure a solid foundation for safe and effective patient care. Our overall objectives for this proposal are to identify attitudes and barriers to data-sharing policies among key addiction research stakeholders and to investigate the reproducibility of addiction clinical trial results. The rationale underlying the proposed research is that reproducibility, which is a cornerstone of scientific advancement, is essential for validating research findings and improving patient care and clinical decision making. We plan to achieve the intended objective of this application by pursuing the following specific, independent aims: (1) identify key factors contributing to both endorsement of and resistance to data-sharing policies among addiction journals and funding agencies; (2) evaluate the effect of journal policies, perceived threat level, and gender of the requestor on the compliance of trialists to share data; and (3) evaluate the reproducibility of clinical trial results from original trial data. The proposed research is innovative for the following reasons: (1) we will be the first to collate, map, and synthesize guidance documents related to data sharing in addiction; (2) we expect to set a new precedent for quality, reproducibility, and transparency in addiction scoping reviews by adhering to the new scoping review extension to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA-ScR) reporting guideline; (3) we will conduct the first prospective trial to investigate factors influencing data-sharing practices; (4) this proposal contains the first investigation of the reproducibility of addiction clinical trial results from shared data; and (5) our proposal is the first to attempt a replication of secondary endpoint results of clinical trials. This project is significant because it will comprehensively identify the fundamental barriers to irreproducible addiction research. We anticipate that completion of these aims will yield the following expected outcomes. First, by summarizing key factors that promote or prohibit data sharing, we expect to contribute fundamental knowledge for the vertical advancement of data-sharing policies in addiction research. Second, by testing addiction trialists’ data-sharing practices, we expect to contribute fundamental knowledge that will increase the uptake and adherence to data-sharing policies. Last, by attempting to reproduce available addiction clinical trial data, we expect to diagnose barriers to reproducing trial results. Overall, we expect that our findi ngs will have a positive impact on the quality and reproducibility of addiction research. Collectively, we expect to further the goal and mission of the National Institute on Drug Abuse (NIDA) to improve the reproducibility of addiction research. The proposed research is relevant to public health because the identification of key factors and conditions that promote data sharing in addiction science is ultimately expected to lead to more transparent and reproducible research. Should the reproducibility of addiction research be improved, clinicians and patients will have increased confidence in the therapies used to treat patients. Thus, the proposed research is relevant to the part of the National Institutes of Health (NIH) mis sion that pertains to promoting the highest level of scientific integrity, public accountability, and social responsibility in the conduct of science.