This paper reports the results of an ethnobotanical survey on the uses of medicinal plants by inhabitants of two southern Ecuadorian provinces, namely, Loja and Zamora-Chinchipe. In this region, two surviving ethnic groups, the Saraguros and the Shuars, and the descendants of a now extinct culture, the Paltas, have been identified. The present study reports a total of 275 plant species, having 68 different therapeutical uses.