The impact of pulp aeration on chalcopyrite flotation in chalcopyrite-pyrite pulps containing different pyrite content (0-80 wt.%) and using xanthate as a collector is reported. Laboratory flotation tests showed significant improvement in chalcopyrite flotation performance under moderate aeration conditions but a significant decrease of performance under highly aerated conditions. The amount of air required to achieve good chalcopyrite flotation recovery correlated positively with the mass fraction of pyrite in the pulps. The greater the wt.% pyrite in the chalcopyrite-pyrite pulp, the longer the aeration time required. A simple model for xanthate and oxygen interactions with chalcopyrite and pyrite has been proposed which follows the trend of chalcopyrite flotation behaviour in chalcopyrite/pyrite mixtures under aerated conditions. (C) 2014 Elsevier B.V. All rights reserved.