This paper is an original empirical attempt to explain the outcome of collective action in the domain of food safety. We examine conditions and institutions that influence pesticide residue levels in vegetables using econometric analysis on data gathered from 60 farmer organisations in Vietnam. Findings suggest that collective action affects safety in that it provides members with technical assistance and monitoring for pest management at the farming level. They confirm the U-shape hypothesis of the effect of group size on safety performance which derives from the trade-off that exists between economies of scale and free-riding. The contribution of public authorities and ecological conditions to food safety remains controversial, while market forces do not yet seem able to drive the production of safer vegetables. (Résumé d'auteur)