The briefing note provides an overview of the progress made and existing gaps in the field of judicial co-operation in criminal matters. It first reviews perceived difficulties with the pillar structure and examines the amendments that the Reform Treaty - due to be formally adopted at the European Council in December 2007 - would introduce. The different approaches to co-operation at a European level, i.e. mutual legal assistance, mutual recognition and approximation are also analysed. A particular emphasis is placed on current legislative proposals and other developments, such as the current state of play of the European Arrest Warrant, Eurojust and the European Judicial Network in criminal matters. Finally, the EU external relations in the field of judicial co-operation in criminal matters are also briefly mentioned.