This article focuses on the social relations among whites, native peoples, slaves, and runaway slaves in the Brazilian province of Espirito Santo during the first half of the nineteenth century. In particular, it seeks to explain how these interethnic relations contributed to the proliferation of runaway slave communities ("quilombos") during this period. From the documents which have been analyzed, Espirito Santo’s wilderness ("sertao") appears to be the scene of an interesting social-ethnic interaction among landlords, Indians, and enslaved Africans beyond the simple common view of a place of "barbaric peoples," renegades and criminals. In this contact zone, two forms of social-ethnic alliances stand out and deserve to be studied more carefully: settlers and Indians fighting against the runaway slaves hidden in the forests, and the armed slaves and settlers fighting the Indians. The research is based on documents obtained from Arquivo Publico do Estado do Espirito Santo.