Direct measurement of load behaviour has provided increased insight into milling operations, A facet of load behaviour of particular importance to simulation and design of mills is the axial mixing of the load. Three different experiments have been conducted on an industrial autogenous grinding mill. The axial mixing model has been fitted to the data obtained from these experiments. It was found that the slurry movement in the mill tends towards rather than a more mixed situation with a vessel dispersion number, N-d, varying between 0.03 and 0.45. (C) 2002 Elsevier Science B.V All rights reserved.