Since the beginning of the 90s, institutional changes are a key question for family agriculture development researches. The point is not only to know if smallholders can improve their production systems but also to evaluate the capacity of traditional institutions to become modern organizations. This study shows the necessity to work on those two changes : technical and institutional changes. Family agriculture development is based on this double process, each one is a condition for the other. The transaction costs theory is used to understand the development of the agriculture in a small region of the Brazilian Center-West part. First, the research deals with the origins of family farmers and the different institutions which lead to the recent transformations. Secondly, the present production units and local organizations are studied. Changes in the factors'prices leads the producers to intensify their production systems but such improvements requires institutional changes. This is the only way to reduce transaction costs. New organizations take place but their action remains limited by the diversity of farmers : they manage to reduce transaction costs but they also have to face increasing coordination costs.
