In the last two decades there have been many examples of co-operation between national stock exchanges in Europe. However, most of these have been cooperation on a very low scale. Starting in 2000, this pattern seems to have changed. Stock exchanges have committed themselves to “alliances”, or even “mergers”, entailing a co-operation which is far more intensive than most former examples of co-operation. In the last couple of years many such alliances have been formed, some have been dissolved, and even more have been considered.