In the summer of 1961 in Sion (Valais, Switzerland) the slabs of a prehistoric tomb appeared in a pipe trench at the Avenue du Petit-Chasseur. While uncovering them, someone exclaimed: “prehistoric engravings!”.The first funerary stela of the megalithic site had been discovered. The excavations, first conducted by Olivier-Jean Bocksberger, high school teacher at Aigle, then by Alain Gallay of the University of Geneva, lasted about ten years. Patiently reconstructed by the scientists, the eventful history of this necropolis made it possible for the rites, the beliefs and the social structure of these prehistoric communities in Valais to be studied in detail. Later, between 1987 and 2003, further investigations were carried out in the area and added to the discoveries. In order to commemorate the 50th anniversary of the discovery of the site, a scientific committee consisting of the representatives of the Archéologie cantonale and the Musées cantonaux du Valais, and of the University of Geneva and the Association valaisanne d'archéologie organised several events during autumn 2011. An international conference was held from 27 October to 29 October in Sion, at the François-Xavier Bagnoud hall. The necropolis of Sion still remains a key reference for the understanding of the Final Neolithic period, not only in the Alpine countries, but also throughout Europe. The scientific meeting therefore focused on the end of the Neolithic period in Valais and in the adjacent regions, on the Bell Beaker phenomenon (a European culture?) and on the funerary rites of this period whereas the doctoral course dealt with the end of the Neolithic period in Valais and with the anthropology of megalithic societies. The conference was attended by nearly 200 people, students, junior and senior scholars from many countries including Austria, Belgium, Spain, France, Hungary, Italy, Morocco, the Netherlands, Poland, the Czech Republic and Switzerland. Thirty-eight papers were grouped into five sessions each preceded by an introductory one-hour conference: Fifty Years of Discoveries at the site of Sion/ Petit-Chasseur; The Neolithic in Valais and its Neighbouring Regions presented by Alain Gallay; Is the Bell Beaker Culture a European? Economy, Culture and Society by Maxence Bailly; Funerary Rituals during the Final Neolithic and the Bell Beaker Period by Henri Duday; and Anthropology of the Megalithic Societies presented by Alain Testart. The present volume reports on these scientific presentations and the ensuing lively debates.