This paper discusses popular participation in health from the point of view of an experience in dengue epidemic control in the late 1980s and early 1990s in the city of Rio de Janeiro. It refers specifically to a social movement called "Se Liga Leopoldina", combining professionals (from health services and public schools) and members of popular organizations from the suburban neighborhoods served by the Leopoldina railway. The paper reviews the ideas motivating actions undertaken by the movement, principally the role of popular organizations in the control of endemics. It calls attention to the danger of preconceived notions when analyzing participation by members of popular organizations in the social movement. The author also calls attention to the fact that social scientists researching social movements should focus on being part of a wider social network of conviviality rather than seeing their role as educating members of the popular organization. Such networks should seek to strengthen and expand social support for the endemic control process.