Experimental results from cross-flow filtration of a dilute bentonite suspension with three different commercially available microfiltration membranes are reported. Using a small laboratory set up, equipped with an automated data acquisition system, the time traces of five parameters were recorded : pressures at feed inlet, tangential and filtration outlets and tangential and filtration flow-rates. The initial transient effects are due to cake accumulation above the filter and not to plugging of membrane pores in the filter. Steady state conditions can be ensured by a tangential outflow of the dense cake with non-Newtonian viscosity. The observed behaviour is consistent with the predictions of the convective model.