This article explores elements that characterize and boost the Solidarity Economy, based on a comparative analysis of experiences in Latin America and North America. The diversity of models and purposes are underlined so as to demonstrate the main approaches and concepts regarding the so-called new expressions of alternative economies. In the South, these initiatives integrate economic and social dimensions, due to their socio-cultural foundations, and also to their specific rationality, in which efficiency and welfare, productivity and participation are inextricably linked. In the United States, an innovative example from the North, new social dynamics are currently developing in a convergent way, such as worker's cooperatives often associ...