Electrochemical potential is considered an important parameter for controlling the recovery and selectivity of sulphide minerals during flotation. The aim of this work was to use mineral potential measurements to gain an understanding of respective mineral flotation performance in the processing of a platinum group mineral (PGM) bearing ore, whilst manipulating the chemical conditions in the pulp. Sulphide mineral potentials were logged during the conditioning stage of the flotation tests. Varying the milling environment and conditioning pH affected the chemical conditions in the pulp. At any condition the mixed potential of the mineral electrodes varied, spanning a range of approximately 100 mV, and increased as follows: pyrrhotite, pentlandite, chalcopyrite, pyrite and platinum. The addition of CuSO4 caused the potential to increase, whilst the addition of xanthate caused to the potential to decrease. The magnitude of the changes in potential for the various mineral electrodes on reagent addition was not the same and followed the recovery trend of the minerals viz. chalcopyrite > pentlandite > pyrrhotite. Chalcopyrite recovery was unaffected by differences in milling media and conditioning. Pyrrhotite flotation was inhibited when the ore was milled in the plant circuit even though the mixed potentials were similar to those measured in laboratory milled pulps. This was presumably due to excessive oxidation in the grinding and classification circuits of the plant. Acid conditioning improved the recovery of pyrrhotite through cleaning the mineral surface from hydrophilic iron oxy/sulphoxy species and also showed an enhanced reaction with xanthate. Pyrrhotite flotation was only slightly inhibited when its mixed potential was below the equilibrium potential for dixanthogen formation. (C) 2002 Published by Elsevier Science Ltd.