When incompatible surfactants are combined to serve as micellar templates for porous metal oxides, a large variety of organizations of the surfactants can be imagined. These include (1) a single type of particle with a mesophase determined by the majority surfactant and a morphology determined by the minority surfactant, (2) completely demixed particles, each containing different surfactants and different mesophases, (3) a single type of particle composed of a mixture of separate phases formed by the two surfactants, (4) a single type of particle in which separate micelles composed of the two types of surfactants mix into a single disordered phase, and (5) a single type of particle in which the two demixed surfactants organize into a novel mesophase. We will show that silica particles with any of the first four structures can be prepared by the hydrolysis of tetraethoxysilane in aqueous ammonia in the presence of mixtures of 2-perfluorooctylethylpyridinium chloride and cetyltrimethylammonium chloride. The first type of particles is formed under mildly alkaline conditions, without added salts or alcohol. The second is favored by a moderate amount of ethanol, although excess ethanol leads to surfactant mixing. The third type of particle is formed by increasing the ammonia concentration. The fourth structure is formed by adding salts. These results are discussed in terms of the effects of additives on micelle mixing, precipitation rate, and partitioning between the bulk solution and the precipitated phase. The third and fourth structures are of particular interest for their controlled bimodal mesopore size distributions.