The effects of the pore geometry on yeast cell fouling during microfiltration were studied using novel micro-patterned membranes having well-defined slot-shaped or circular pores. Normal flow filtration experiments were performed with Baker's yeast suspensions. The flux decline data were consistent with initial fouling by pore blockage followed by cake filtration. The specific resistance of the cake layer was a function of both the pore geometry and the overall membrane porosity. The initial rate of flux decline was slower for the membrane with slotted pores compared to the membrane with circular pores since the initial cell deposition only covered a small fraction of the slotted pore due to its high aspect ratio. The data then show a transition to cake filtration, with the nature of the transition also a function of the underlying pore geometry. A simple geometric model was developed to describe the cake growth phenomenon on slotted pore membranes. These results provide important insights into the effects of pore geometry on membrane fouling. (c) 2006 Elsevier B.V. All rights reserved.