This report gives an academic insight on the social and economic transformation of Chamonix, the most important tourist place of the Alps, during the last fifty years (1950-2000). It especially focuses on demographic evolution (strong increase up to the 1980’s), economic and spatial development (rise of tourist activities and decline of agriculture et industry, huge increase in tourist flows, urbanization of the bottom of the valley), social and cultural transformations (strong immigration, adaptation of local people to the growth of tourism), and the adaptation of public regulation (a stronger involvement of the municipality in the tourist board and the ski-lift corporations). It underlined the following problems: - Urbanization and the increase of the price of land, houses and flats made more difficult for local people and young workers to live in Chamonix, and for local families to keep or share between their young members local properties; - A increase number of hotels, restaurants and shops are owned or managed by inhabitants recently settled in the valley. The turnover of these activities is huge and a growing proportion of owners come, live and work in Chamonix only for a few years, mainly for making money, and leave for elsewhere. A growing part of these activities are owned by British. - The definition of the local identity has been strongly questioned since the 1980’s. Local families find more and more difficult to feel “at home” with the growing number of tourist and foreigners. - The municipality, mainly in the hand of local families, managed to remain the main stakeholder in various fields – spatial planning, ski-lift management, tourism office, cultural events and equipments. But doing so, it became difficult for small enterprises and foreigners to play a role in public space and collective organisation. Though undertaken in a very specific alpine tourist place, this case study, analysed with social networks and governance theories, proved how important can be the side-effects of tourist development on local people, especially young people, and the part of local identity in the making (or the limitation) of collective processes able to involve incomers.