Our research looks at a voluntary association’s involvement in preventing cardiovascular diseases. The development of the health system in the wake of scientific progress, constant political change, and shifting currents of thought and interests means that, since the 1950s, health has been considered from a biomedical angle. This legitimizes the dominant position of experts. What place do laymen have in managing the risks of chronic disease? What are their representations of health? How do they take on domestic health work, through which they often interiorize new standards and rules of life, and modify their health behavior? We gain conceptual and theoretical insight through anthropologically immersive fieldwork carried out within an association, observing various preventive interventions. We also carried out conversations with ill or formerly ill volunteers. All this clarified certain aspects of the problem. The efforts of the volunteers makes sense when seen through the concepts of gift, counter-gift, and socialization in a new health under the influence of the symbolism of rites of passage, and of testimony about the distribution of educational messages. The activity of the volunteer is transformed by a logic which is far from philanthropic. They become a mediating health agent. They perform genuine organization, management, negotiation, and training work, which fills a space otherwise neglected by experts in health prevention and education.