The high-flux dynamic microfiltration of an oil-in-water emulsion was studied under constant pressure by using a rotating cylinder type membrane filter with a suspending particle bed in the filter chamber. Using this dynamic filtration, much smaller hydraulic cake-resistance can be obtained than that encountered in conventional operation. It was quickly discovered that, due to the powerful sweeping force acting on the fouling cake-layer, the dynamic effects of the additional suspended solids yield remarkable improvements in the microfiltration flux of poorly filterable O/W systems.