Results are reported from a study of the effect of the antimonate content of sulfides on oxidation activity, pH, and oxidation-reduction potential (E h ) in bacterial oxidation. A comparison is made between the bacterial-oxidation parameters of selective arsenic and antimony concentrates and a collective sulfide concentrate. The study results show that the kinetics of bacterial oxidation of the arsenic concentrate can be improved significantly by performing flotation in accordance with a new flow scheme that extracts The processing of persistent gold-bearing ores includes collective flotation of the sulfide minerals in the ore, bacte- rial oxidation of the concentrates, and cyanation of the cakes obtained by leaching. During bacterial oxidation, the sulfides dissolve and the gold in them is opened up and becomes accessible for cyanation. The technological indices that are obtained in processing ores of the given type depend to a large extent on the degree of oxidation of the sulfides, since cyanide is con- sumed in reactions with the other sulfides - especially antimonate - in the alkaline medium. This increases the cost of the processing and decreases the amount of gold that is recovered. Sulfides differ from one another in their electrode potential and composition and the structure of their crystalline lattice. The proportions of the different sulfides in the concentrate dur- ing the oxidation stage determine the electrochemical interactions between the minerals, the quantities of reagents that are consumed, the reaction products which are formed, and the ionic composition of the medium. The latter in turn affects the parameters and kinetics of the bacterial leaching operation (1). Of the various sulfide minerals present in the concentrates obtained by flotation - antimonate, pyrite, arsenopyrite and pyrrhotine - antimonate has been studied the least in regard to its effect on bacterial oxidation. Here, we study the effect of the antimonate content of the concentrate on the rate of bacterial oxidation of Fe 2+ , the pH values, and the oxidation-reduction potential (E h ) in the bacterial leaching of sulfides extracted from persistent gold-bear- ing ores. Bacterial oxidation was carried out with the use of synthetic compositions of sulfide minerals containing arsenopy- rite, antimonate, pyrrhotine, and pyrite in different proportions (Table 1). The sulfide minerals used for the studies were recovered from crushed gold-bearing ore. An increase in the amount of antimonate in the minerals is accompanied by a decrease in the contents of the other sulfides and iron, sulfur, and arsenic (Table 2). The composition of the No. 4 minerals was closest to the content of sulfides in the collective gold-bearing concentrate obtained from the ore at one of the gold- extraction plants in Russia.