The objective of this study was identifying culture, perceptions and practice of significant stakeholders in terms of data sharing as well as use of existing data of clinical trials. Relevant stakeholders were identified: clinical trialists, funders, editors of scientific journals, institutions, pharmaceutical industry and consumers. Barriers and opportunities for opening clinical trials' data and their reuse were analyzed. Research method was in-depth interview. Participants were recruited from defined groups regarding their availability. Interviews were recorded, transcribed and analyzed using NVivo software. Data collected in interviews complemented the information provided in the previously filled in questionnaire. Three researchers have coded the answers and then reached consensus. We have analyzed the main three codes: 'culture', 'barriers' and 'solutions'. Study has shown that data sharing and reuse are needed for further science development; international standards are to be developed and all stakeholders must be engaged. Education will influence the change of culture regarding transparency. Nevertheless, it is needed to revalue studies that use existing data and enable their funding. This study is part of IMPACT Observatory.