In this article we seek to systematize historical and ethnographic informations about mbyá presence in the Guaíba hydrographic area (Rio Grande do Sul/Brazil), taking into account the relations between indians and non-indians through the process of territorial configuration of Bacia Platina. This discussion is based on fieldwork, literature and primary sources about three contemporary mbyá occupations -- Petim, Passo Grande and Arroio do Conde.