Cellular ceramic membranes have a structure which resembles that of foams. This is not surprising, since a polymer foam is frequently used as a precursor in the manufacturing process. Like all membranes, the processing characteristics are determined to a large extent by the interaction of particles in the suspension or mixture to be treated with the pores of the membrane. If the particle dimensions are near to the dimensions of the pores, then some particles will be trapped, thereby increasing the hydraulic resistance of the media. This will result, in constant pressure filtration, in a decrease in permeate flux. It is therefore important to be able to predict the passage and retention of particles through the media. The retention on the surface to form a cake and within the media is important and should be differentiated, particularly if cleaning by backflushing is to be considered. In order to investigate particle retention, a definition of the pore structure of the membrane is necessary. In the majority of studies in this field, because of the complexity of the material, a simplified model is used to describe the internal pores of membranes. The pores are assumed to be cylindrical, parallel (and therefore nonconnecting) capillaries. This is quite inappropriate for the membranes considered in this paper. The pores are formed from a highly connected network of shapes with varying size and cross section. In this work, a model to simulate the foam structure is briefly presented and then used to investigate conditions for microfiltration of near-pore-sized particles.