An investigation into the effect of microwave radiation on the processing of a massive sulphide copper ore has been carried out. It is shown that significant reductions in the Bond work index can be achieved without any discernible adverse effect on the subsequent flotation process. A maximum reduction in work index of 70% was achieved after microwave exposure for 90 s. Microwave exposure followed by water quenching is shown to reduce the work index by up to 15% more than for unquenched samples. Initial trials on the effect of mass loading on the reduction in work index indicate that there exists an optimum mass of material that can be pretreated effectively by microwave radiation in any microwave cavity. Process simulation on the package USIMPAC showed significant flowsheet changes are possible as a result of exposure to microwave radiation and the subsequent reduction in work index. Conclusions are made regarding the economic implications of microwave pretreatment on the flowsheet. (C) 2001 Elsevier Science B.V. All rights reserved.