The flotation and separation of sulfide minerals can be detrimentally affected by the oxidation of the surface of these minerals. The surface oxidation products consist mainly of metal hydroxides and sulfur-oxy species, either adsorbed in thin layers or precipitated from solution as colloidal particles. The amount of surface oxidation will reduce the hydrophobicity of the mineral and make the adsorption of collectors less selective. The interaction between these oxidation layers and the mineral is generally weak electrostatic and/or hydrophobic in nature. ln this study, various methods were used to remove oxidation products from the surface of several sulfide minerals. The effects of mineral treatment by mechanical (sonication or attrition by quartz) or chemical (pH change or use of complexant) methods on mineral flotation were investigated and correlated with the amount of oxidation product removed from the mineral surface. It was also shown that these ＇＇cleaning＇＇ methods were selective in removing oxidation products in mixed mineral systems.