The effects of additives (sodium hydroxide, sodium carbonate, sodium oleate, oleic acid and poly(acrylic) acid), on stirred media milling of limestone have been investigated. The results are evaluated in terms of specific surface area, specific energy and energy efficiency as a function of additive dosage, polymer molecular weight, solids concentration and relevant operating variables. Use of additives generally results in changes in specific surface area and energy efficiency, while under certain conditions a more than 100% increase in these parameters can occur. Relevant interfacial properties have been measured and the milling mechanisms involved are explored, particularly in terms of the effect of additives on the flow patterns at higher solids concentration.