Wet ultrafine grinding has been increasingly used for production of ultrafine powders in various industries. It has been known that slurry rheology significantly influences the grindability of industrial minerals in wet ultrafine grinding. This review represents some previous work with respect to slurry rheology in ultrafine grinding. In this review, some methods for the characterization of the slurry rheology and some empirical equations modelling rheological behaviours of slurries were presented. The semiempirical model incorporating slurry rheology, solids concentration, particle size and slurry temperature was described. In addition, on-line measurement for the slurry rheology control was also discussed. In the case of ultrafine grinding, various parameters (such as solid concentration, particle size and distribution, particle shape, temperature, rotation and pH, use of dispersants), which affect the slurry rheology, have been described. It was revealed that the optimization of the rheological behaviours of slurry in ultrafine grinding could increase throughput, energy efficiency and product fineness as well. It is suggested to further study the mechanisms of slurry rheology in the presence of chemical dispersants in wet ultrafine grinding. It is desired to develop a model, which can represent a relation among slurry rheology, comminution parameters, amount of dispersant, energy efficiency and particle size characterization.