Miniemulsion droplets were stabilized with a mixed emulsifier system consisting of an anionic surfactant such as sodium dodecyl sulfate and a costabilizer, which is typically a low-water-soluble, long-chain alkane or alcohol such as hexadecane or hexadecanol. The surfactant, anionic in nature, provided an electrostatic barrier against coagulation, and the costabilizer retarded molecular diffusion of the monomer or Ostwald ripening. The coagulation mechanism operative for the stabilization of the miniemulsion droplets is theoretically considered here. The understanding provides insight into the role of the surfactant. The fate of the miniemulsion droplets during the course of polymerization is also discussed. (c) 2008 Wiley Periodicals, Inc.