The IVth meeting of an international workgroup will gather together, in Rennes, from 10 to 12 May 2012, several of the leading European specialists on the theme of megalithic monuments (about twenty speakers from some ten different nationalities). Following the international colloquium at Bougon (Deux-Sèvres) which was held in 2002 (Joussaume, Laporte, Scarre, 2006), meetings of the European Megalithic Studies Group took place in Göteborg in Sweden ( 2004 ), in Seville in Spain ( 2008 ) and in Kiel in Germany ( 2010 ). This will be the first time for more than thirty years that the city of Rennes will welcome a high-level scientific meeting specifically dedicated to the study of megalithic monuments. It is organized within the framework of a program entitled " Megalithic monuments of the Atlantic zone and beyond " which is supported in particular by the Maison des Sciences de l'Homme de Bretagne. It will comprise two days of oral communications, open to the general public, in the Auditorium of the Museum of Brittany, in Rennes. They will be accompanied by the presentation of posters about current work on megalithic monuments in France, in Europe and in the World.