Total mercury and selenium concentrations were determined in hair samples collected from Wari (Pacaas Novos) Indians living in Doutor Tanajura village, Gujara-Mirim city, Rondonia State. The mercury concentrations in some samples are much higher than the values determined in samples from individuals not exposed to mercury contamination, occupationally or environmentally. The selenium concentrations are in the normal range. A correlation was observed between the mercury and selenium concentration and the values of the molar ratio approach 1 at low Hg concentrations. This fact is related to the equimolar complex formed by {(Hg-Se) n } m -Seleprotein P, which can decrease the bioavailable mercury in the organism.