Enlargement poses a number of institutional challenges to the European Union: institutions originally established for six member states need to be adapted to cope with an EU of between 20 and 30 members. This poses questions both about their size, and about the procedures for taking decisions. The eleventh Monitoring European Integration report will evaluate the reforms adopted at the Nice summit and highlight a number of structural and institutional reforms that were ignored for political reasons. It also argues that enlarging an insufficiently reformed EU may provoke crises whose solution might actually lead to a better EU. The authors conclude with an analysis of the emergency measure that should be taken, before enlargement occurs.