accepted after revision 15 February 1995Studies were made of the grinding kinetics of chromite ore in a stirred ball mill. Grinding tests were carried out using material in discrete size ranges (-53+38 mu m and -38 + 25 mu m) and for material conforming to a natural spread of sizes (-100 mu m). Tests conducted on the discretely sized material were used to establish the breakage function for the ore. Specific selection function parameters were established by milling the -100 mu m material for various inputs of energy. The population-balance model derived from the test results yielded good agreement between the measured and fitted product size distributions. A relationship was established between the specific selection function and the pin tip velocity, ball density and ball size.