The review paper deals with the results of the utilization of mechanical activation in hydrometallurgy. The definition of mechanochemistry is given as well as physicochemical changes in mechanically activated minerals are described. The enhancement of the leaching processes in hydrometallurgy is illustrated. The chemical and bacterial leaching of sulphide minerals are given as examples. A brief description of the established technologies (LURGI-MITTERBERG, ACTIVOX(TM), MELT) applying mechanical activation for metals extraction is given. In these processes, the introduction of mechanical activation step into technological cycle significantly modifies the subsequent processing steps. (C) 2003 Elsevier B.V. All rights reserved.