Precious metals distributionin the Precambrian mafic-ultramafic layered complex of Niquelândia, central Goias, Brazil, has been investigated by flameless Atomic Absorption Spectroscopy. The contents of Ag, Au, Pd, Pt, Rh and Ru were determined in the different units of the complex, mainly in the basal peridotite and the layered ultramafic zone constituting the ultramafic portion. In the latter zone (27 analyzed samples) average contents for Ag, Au and Pd are 70, 30 and 15 ppb, respectively. In most samples Pt, Rh and Ru are below 10 ppb. The precious metals are very unevenly distributed and their concentrations in individual samples appear controlled- by the amount of sulphides. The variations in average composition appear to be related to stratigraphic position and/or rock composition. Ag and Au tend to concentrate in sulphide-bearing pyroxenitic horizons of the upper gabbroic zone. The Pt-group elements mainly concentrate in peridotitic layers within the ultramafic portion. Factors affecting the geochemistry of the precious metals during the fractionation of mafic magmas are discussed. The influence of structural features (i.e. the polymerization state) of the silicate liquids in equilibrium with the sulphide phase is emphasized.