Poly(methyl methacrylate) and poly(butyl acrylate) lattices have been synthesized under ultrasonic irradiation in the presence of a cationic surfactant, dodecyltrimethylammonium chloride. The polymerization of oil-in-water emulsions of monomeric species was carried out at 30 degreesC (+/-5degreesC) in the absence of a chemical initiator. The lattices were formed as stable dispersions with particle diameters spanning the range of 40-150 am and with polymer molecular weights greater than 10(6) g mol(-1). The results obtained strongly support a polymerization process involving a miniemulsion system, in which continuous nucleation of particles takes place throughout the monomer to polymer conversion reaction.