The bioleaching of flotation concentrate is a new method for copper recovery that could form the basis of an economic and environmentally friendly process. The main objective of this work was to evaluate a bioleaching process from the treatment of two concentrates, (i) a copper gold bearing concentrate and (ii) an ordinary copper flotation concentrate, using mesophilic bacteria. The special gold-bearing copper flotation concentrate was obtained from the Polkowice Mine. The second material was an ordinary copper flotation concentrate purchased from the Lubin Mine. Bioleaching experiments were carried out in 250 ml Erlenmayer flasks and a rotating bioreactor (biorotor). The most important operating parameters were copper dissolution (%) and surface area. A culture of Thiobacillus ferrooxidans was used for the bioleaching tests. The bioleaching maximum was obtained at both 12% and 15% of the solid. The effect of pyrite addition on the kinetics of copper concentrate bioleaching was also investigated. It was established that 3% of pyrite causes an increase in the bioleaching process. In the case of ordinary flotation concentrate bioleaching, 65% of the recovery was obtained-at ' the-initial stage (48 h). In the second stage, the copper recovery slowly increased and after 312 h 86% of the copper recovery was obtained. On the other hand, the surface area of copper concentrate initially increased (at 24 h it was 8.67 m(2)/g) and then slightly decreased in the second stage. (C) 2003 Elsevier Science Ltd. All rights reserved.