This article attempts to describe the process of strutuctarion of social networks in voluntary associations. Departing from an empirical survey in NGOs in the city of Recife, we investigate how social networks are built and the influence of their design in the action of NGOs. Firstly, we conclude that the relevance of the mission of the NGOs is not an essential element in mobilizing external ressources. To a great extent, the success of their action depends on the capacity they develop of atracting institutional ressources (from the State, the Church, International Cooperation, etc.) Second, the structuration of these networks makes possible the compairason of the relationship between the establishment of the agenda of these NGOs and the existence of conflict between this agenda and the purposes established at their original mission.
