There seems to be a growing tendency, as prominently shown by the fall of the Santer Commission in 1999 and more recently in the Constitutional Treaty, to construe the relationship between the Commission and the European Parliament as a parliamentary system. In a parliamentary system, the government gives account to Parliament and, where appropriate, suffers the consequences if errors have been made. The aim of this project is to further develop a European concept of political accountability. Therefore, it can be relevant to identify what political accountability precisely means in the various Member States. In order to identify common principles (ius commune), twelve distinguished constitutional lawyers and political scientists have analysed the concept of political accountability from their national perspectives. In a comparative chapter, the parallels and the differences between the national systems are identified and the extent to which common ground can be found in Europe is explored. In a final chapter, an analysis is made of the extent to which this ‘ius commune’ can be applied to the EU-level.