Gold losses in the cyanidation of refractory ores are mainly due to the presence of sulfide and carbonaceous materials. Sulfide minerals in the ore can be oxidized by hypochlorite generated electrochemically in the leaching reactor. The electrooxidation of a gold-bearing sulfide concentrate that contains pyrite, pyrrhotite and arsenopyrite was investigated in an electrochemical cell with 10% (by weight) NaCl electrolyte. The relative amount of iron dissolved by the oxidation of sulfide minerals increased with the duration of the test under constant applied current and leveled off at about 80% after 8 hours. Increasing the pulp density increased the current efficiency and the total amount of material oxidized. Cyanidation tests after 38% iron removal by electrooxidation resulted in a gold extraction increase of approximately 29% and a cyanide consumption decrease of about 31%.