The US government creates astonishingly complete records of policy creation in executive agencies. In this article, we describe the major kinds of data that have proven useful to scholars studying interest group behavior and influence in bureaucratic politics, how to obtain them, and challenges that we as users have encountered in working with these data. We discuss established databases such as regulations.gov, which contains comments on draft agency rules, and newer sources of data, such as ex-parte meeting logs, which describe the interest groups and individual lobbyists that bureaucrats are meeting face-to-face about proposed policies. One challenge is that much of these data are not machine-readable. We argue that scholars should invest in several projects to make these datasets machine-readable and to link them to each other as well as to other databases.