Computer printed circuit boards (CPCBs) have a rich metal content and are produced in high volume, making them an important component of electronic waste. The present study used a pure culture of Acid-ithiobacillus ferrooxidans to leach Cu and Ni from CPCBs waste. The adaptation phase began at 1 g/l CPCBs powder with 10% inoculation and final pulp density was reached at 20 g/l after about 80 d. Four effective factors including initial pH, particle size, pulp density, and initial Fe3+ concentration were optimized to achieve maximum simultaneous recovery of Cu and Ni. Their interactions were also identified using central composite design in response surface methodology. The suggested optimal conditions were initial pH 3, initial Fe3+ 8.4 g/l, pulp density 20 g/l and particle size 95 mu m. Nearly 100% of Cu and Ni were simultaneously recovered under optimum conditions. Finally, bacterial growth characteristics versus time at optimum conditions were plotted. (C) 2014 Elsevier Ltd. All rights reserved.