This chapter discusses the protection of relevant data and issues that might block access to such data. There are at least three kinds of data, data specifically generated for the purpose of AI, big data, and copyright-protected data. Data specifically generated for AI should qualify as works worthy of copyright protection as compilations. If such data are public-sector information, measures that may facilitate the widest re-uses of public data should be taken. If such data are from the private sector, attention needs to be paid to whether these data are of critical importance and whether the use of competition law and/or ex ante regulation will be needed to ensure access. The issue of protection of big data should not be addressed in the sense of giving proprietary entitlement over big data to any entity. When looking at the private-sector components of big data, there are legal, technical and market factors working against the formation, accumulation, and free flow of big data. When looking at the public-sector components of big data, both the importance of open data and the re-use of public sector information come to the fore. Concerning the issue of accessing big data, there are barriers to its collection, storage, synthesis, analysis, and usage. However, behavioural barriers warrant special scrutiny. In that regard, competition law as an ex post remedy can be relied upon but is of limited use; therefore sector-specific regulation might be needed. As for copyright-protected data, the real issue is more about access than protection.