This research was designed to investigate zinc and lead extraction by combined sequential biooxidation and acidic brine leaching from a raw complex sulfide ores containing sphalerite, pyrite, and galena. For the biooxidation, the zinc dissolution from the sulfide ores by the adapted bacteria was examined. The effects on ore particle size, pH, pulp density, and temperature on bacteria] leaching was studied systematically. From the experiments it was shown that about 95% of zinc was extracted after 20 days of bioleaching at 30 degreesC. Subsequently, 98% of the lead was extracted from the bioleached residues using an acidic sodium chloride solution as the lead lixiviant at a temperature of 60 degreesC for 90 min leach. Leaching kinetics indicated that diffusion through the product layer was the rate controlling process during zinc bioleaching, and that the overall rate of chemical reaction at the surface was the rate controlling process during lead brine leaching. The relative activation energies of the overall rate during the two different leaching stages were calculated to be 32.09 and 44.35 kJ/mol, respectively. (C) 2003 Elsevier Ltd. All rights reserved.