Tests were performed to evaluate the galvanic interaction of synthetic mixtures of galena (valuable mineral) and pyrite (gangue mineral) on their flotation response, both in air and nitrogen atmospheres, when the anionic collector sodium-di-isobutyl dithiophosphinate is added. The effect of lead activation of pyrite is also examined. Floatability of galena from mixtures is similar to that of galena alone indicating that the galena-collector interaction is not affected by the galvanic contact. In the presence of oxygen the floatability of pyrite from mixtures increases slightly compared to pyrite alone, due to the migration of Pb species, arising from galena dissolution, which adsorb onto pyrite as hydrolysed lead species. Galena-pyrite galvanic contact lowers the adsorption of lead species (from a Pb-bearing solution) onto pyrite, compared to that observed with pyrite alone. When the galvanic interaction is weakened due to the absence of oxygen (e.g., by using a nitrogen atmosphere), the concentration of lead onto pyrite surface increases to levels similar to those of pyrite alone. The collector chemisorbs onto galena forming a layer of low electroactivity that slows down the dissolution of the mineral; nevertheless, this layer does not completely prevent the galvanic interaction with pyrite. (C) 2003 Elsevier Science Ltd. All rights reserved.