The research for this paper was conducted in São Gabriel da Cachoeira, in the northwestern Amazon, with the Baníwa indigenous people, in partnership with indigenous organizations, seeking to understand the relations among the group's cosmology, their system of representations of sickness and healing practices, and their transformation through inter-ethnic contact. The recording of myths showed the origin of the diseases and demonstrated the existence of several traditional categories of sickness, guiding traditional healing practices and the incorporation of biomedical knowledge. The Baníwa's cosmology operates like a reception system for biomedical information, which the people grasp according to the logic of mythical thought. Similar cognitive strategies are used to generate the demands that indigenous leaders submit to the Health Councils and Health Services.