The extensive work done on sustainable development and natural resource management has revealed two important facts. First, the analysis of human societies interactions with their environment stressed the importance of efficient co-ordination mechanisms and the dear consequences of the lack of such mechanisms. Second, it appears that preferences on which actors make their choices are not all correctly handled through market processes. Taking these issues into account is not and easy task. Contingent evaluation methods, through the analysis of actors'willingness to pay, and the related approaches often run into the impossibility to define contingent choices clearly perceived by all actors in the same way. In a totally different domain, the multi-criteria methods face limitations linked to the hierarchical non participatory framework supposed by their implementation. Considering the fact that the emergence of sustainable development depends on the existence of an effective mechanism of co-ordination for the different actions influencing a given environment or geographical zone, a team of scientists from CIRAD developed an institutional analysis method enabling the investigation and improvement of the way actors deal with problems of sustainable developement: the PACT (Pro-Active Conciliation Tool) method. This method is based on a phase of interviews and a phase of analysis, which is facilitated by software specifically designed for the purpose. It allows users to analyse actors perceptions in order to identify the framework of their preferences, reveal the areas of consensus and divergence within these preferences and assess the potential role of each of them in a viable process of change. Used in situations where interactions among stakeholders are both diverse, numerous and affect a natural resource or a specific quality of the system considered, this method enables analysts to help actors go beyond their differences of opinion and use best the resources available