The influence of silver and iron concentration and the presence or absence of oxygen was investigated in the silver-catalyzed chalcopyrite leaching. The leaching tests were performed at two different temperatures (35 and 68 degrees C) in stirred flasks (180 rpm) containing 0.5 g of mineral and 100 mL of Fe(3+)/Fe(2+) sulphate solutions at pH 1.8 and at an initial redox potential of 500 mV vs. Ag/AgCl. The addition of a great excess of silver favoured the transformation of chalcopyrite into copper-rich sulphides, such as: covellite, CuS, and geerite, Cu(8)S(5). These sulphides prevented the formation of CuFeS(2)/Ag(2)S galvanic couple and, thus, the regeneration of silver. In addition, oxygen in solution plays a key role in the regeneration of silver ions acting as the main oxidizing agent for Ag(2)S. (C) 2009 Elsevier B.V. All rights reserved.