Two agricultural development projects based on conservation agriculture and agriculture/livestock integration are implemented in Madagascar with both a "watershed approach" and a "farming system approach": the BV-lac project in the area of Lake Alaotra and the BVPI-SEHP project in Vakinankaratra (Central highlands) and South-East. A farming systems reference monitoring network (FSRMN) has been set up with two objectives: i) to help the project in decision making processes for choosing appropriate technologies that will be developed according to a farmer's typology using prospective analysis, ii) to monitor the project's economical impact in the short and medium term. The farming system modelling approach is based on a software developed by INRA-CIRAD-IAMM ("Olympe", JM Attonaty, INRA), The approach is based on partnership (smallholder, farmers' organizations, project operators and local administration), farming system analysis, and modelling for a Decision Support Systems (DSS) project orientation. Adoption of conservation agriculture (CA) represents both a real change of paradigm for local farmers and a real challenge for agriculture and natural resources sustainability.