Crossflow microfiltration is nor normally applied to mineral suspension thickening and washing. However, its use is feasible and relatively high filtrate flux rates can be achieved. Thus it may find application for suspensions that are otherwise difficult to process such as clays and slimes. A semi-empirical model of flux rate with the shear stress on the deposit on the filter is shown to be applicable for the three finely divided minerals investigated here. The model has been extended to provide a relation for deposit depth with operating pressure. This agreed with experimental data when filtering at pressures over I bar, but needs to be developed further for operation at lower pressure. There are several operating modes that may be used for process operation, the selection of the most appropriate one can be based on some simple testwork to obtain the necessary empirical constants coupled with the design and operating equations derived from overall mass balances. The mass balances are based on the assumption that the crossflow system can be treated as a well mixed tank. The experimental evidence suggests that this is a reasonable assumption for both the thickening and diafiltration studies reported here.