Cross-How filtration of bentonite-in-water suspensions is studied experimentally in a small laboratory device. The Theological behaviour and the filtration resistance in batch filtration are independently established. Both transient and steady-state data indicate channel constriction by a dense cake layer. Quantitative estimates based on measured parameters show that steady-state conditions can be ensured by tangential flow of the dense pseudoplastic bentonite cake. Steady-state is possible when the shear stress at the moving boundary feed suspension/dense cake exceeds appr.l Pa (at lower values of the shear stress the cross-flow microfiltration channel gets plugged). The material characteristics of the dense cake, which determine cross-flow filtration behaviour, are the viscosity and the specific filtration resistance. Indirect estimates of these quantities from measured cross-flow filtration parameters are consistent with results from direct measurements. The data support the convective model of cross-flow microfiltration.