Spray drying a mixture of silica and polystyrene latex (PSL) colloids above the decomposition temperature of PSL results in the formation of porous silica particles. By appropriate selection of the experimental conditions, such as the use of a tubular temperature, the weight fraction of colloids, and the flow rate of carrier gas, the resulting silica particles contain organized pores with a hexagonal close-packing arrangement. The process by which organized mesoporous silica particles are formed by the spray-drying method was examined using elementary laws of topology. Although a direct test using experimental data was not performed, at least qualitatively, the existence of a "stationary state" at which organized mesoporous particles can be produced with hexagonal close packing could be defined. Deviation from this stationary state results in the formation of unorganized pores as well as a deformed particle shape, rather than spherical ones. (C) 2004 American Institute of Chemical Engineers.