Previous studies of membrane fouling have often employed one of the classical blocking laws to describe the variation of filtrate flux with time. However, these models implicitly assume that the membrane has straight-through noninterconnected pores, even though most commercial microfiltration and ultrafiltration membranes have a highly interconnected pore structure. We have developed a theoretical model for the effects of pore blockage on the fluid velocity and pressure profiles within membranes having different interconnected pore structures assuming Darcy flow in the porous membrane. Model calculations are in good agreement with filtrate flux data obtained during protein microfiltration using membranes with very different pore morphologies. The results clearly demonstrate that the membrane pore connectivity has a significant influence on the flux decline due to the possibility for fluid to flow around the pore blockage, an effect which has been ignored in previous studies.