In this study, the effect of mechanical activation was evaluated on the leaching efficiency of copper sulphidic concentrate in 0.5 M sulphuric acid medium. The mechanical activation of samples was performed by a high energy planetary ball mill under the atmospheric conditions. The results showed that there was an optimum time of MA, about 6 h, in which the leaching efficiency reaches its maximum value (42% for 7 h of leaching). The improvement of leaching efficiency due to mechanical activation can be attributed to the significant decrease of the size of particles and the intense structural disordering of particles. (C) 2011 Published by Elsevier Ltd.