The database is a unique and comprehensive collection of all infringement proceedings in which the European Commission sent a Reasoned Opinion to the member states between 1978 and 1999. It contains more than 6,300 individual infringement cases, which are classified by infringement number, member state, policy sector, legal basis (CELEX number), legal act, type of infringement, and stage reached in the proceedings (see data). Additionally, there are dates for every step of the infringement proceedings, which allows for research on the persistence of non-compliance. The Commission gave us access to its own database, where we were able to download the data available for the years 1978 to 1999. We completed the database with information from the annual reports of the Commission and judgments of the European Court of Justice. You can access the database by using our search mask (see data). Empirically, we find that the vast majority of infringement cases is solved during the early stages of the infringement proceedings. Of the almost 6,000 cases, which entered the official infringement proceedings between 1978 and 1999, less than one third is referred to the ECJ. Of those 1,675 referrals, the ECJ ruled on 822 cases – in 19 out of 20 times against the member states. Only about 100 cases are referred to the ECJ a second time as member states do not comply with a first judgment of the ECJ in accordance with article 226 of the EC treaty. In fewer than a dozen cases, the ECJ has imposed financial penalties. For a detailed discussion and operationalization of the data see Börzel et al. 2010: 1373-1374. The codebook can be downloaded here (Codebook).