Plantas medicinais em feiras e mercados públicos do DistritoFlorestal Sustentável da BR-163, estado do Pará, Brasil In order to understand the productive chain from extractive medicinal plants marketed at emporiums, fairs and public markets of districts of this area, semi-structured interviews with 20 vendors of medicinal plants were carried out. Species richness was estimated by Bootstrap and similarity among the districts studied was analyzed by Sørensen's Index. 46 medicinal plants belonging to 42 genera and 21 botanical families were identifi ed. Fabaceae, Anacardiaceae and Bignoniaceae were the most representative botanical families. Th e expected richness for the sample was 50 species and additional collecting would increase by at least four items the general list of richness. Santarém, Itaituba and Altamira share a larger number of species and the fi rst is shown to be a diversifi ed center of medicinal products, presenting the largest number of exclusive occurrences (14). Th e fairs and public markets are an important link of this distribution system, and should be included in government actions concerning public policies for health.