The effect of mechanical activation on metal dissolutions by pressure leaching of massive rich copper ore taken from Kure copper ore deposit (Turkey) was investigated. The dissolution efficiencies of sulfide minerals are significantly improved by ultrafine grinding, also known as mechanical activation. This grinding results in decrease of particle size and an increase in crystal distortion of sulfide minerals. Leaching efficiencies of copper, cobalt, and Zinc increased from 45.2%, 25.9%, and 87.7% to 98%, 85%, and 97%, respectively, after 3-h mechanical activation. At the end of the activation, leaching was carried out at a temperature of 110 degrees C, 10-bar oxygen partial pressure, and 150-g/L solid concentration without addition of acid. This study has also indicated that mechanical activation involving fine milling as a pretreatment is not only effective on copper minerals dissolution but also on the dissolution of other associated minerals, such as cobalt and zinc sulfides.