This paper focuses on the notion of endogenous development, a definition of which it tries to provide, despite a lack of “theoretical roots”. Endogenous development refers to 5 others notions: endogenous potentials, regional economy, sustainable development, participation, regional identity. The analysis is based on 2 Swiss case studies characterized by an economic and demographic decline. Tourism is a main field of action with organic farming in order to attract commuters. Various local initiatives are quoted. They're based on local population’s social capital and rely on external influence, external resources, exchanges, internal resources. The importance of networks, norms and rules is stressed by the authors. They also underlined the close interdependence between local and global scale, and the necessity to articule informal and traditional strategies of development.