It is well known that different milling procedures may result in different flotation responses. In the present study, the effect of various grinding conditions such as wet or dry grinding and addition of lime to the mill compared to the flotation cell on the flotation of two different copper sulphide ores was investigated. The milling was carried out in a Magotteaux Mill which enables reagent addition during milling as well as the monitoring of changes in parameters such as pH, Eh and DO during milling. The paper will present grade and recovery results obtained after the different milling procedures. After wet milling, the ores yielded different concentrations of Cu and Fe in the pulp and also significantly different recoveries. Dry grinding affected the behaviour of the ores differently. Proposals are made to explain the results by reference to the mineralogical properties of the two ores.