The domains of homogeneity for the systems containing styrene - alcohol (methanol, isopropanol, t-butanol) - water are investigated. These ones represent the reaction medium of dispersion polymerization The domains of homogeneity increase with increasing the hydrocarbon chain of the cosurfactant and in the presence of surfactants. Conductometric and refractometric studies have established that the homogeneous systems obtained in the presence of monomaleate of nonylphenol ethoxylated with 25 moles ethylene oxide, in a concentration of 10% based on the above-mentioned mixture, are microemulsions with oil-in-water (o/ w) bicontinuous or water-in-oil (w/ o) structure. In the presence of 10% bismethacrylate of PEG 1500 or 5% bismethacrylate of PEG 1500 and 5% acrylic acid, based on styrene, the domains of homogeneity are smaller, but the character of microemulsion is preserved. The latexes prepared by polymerizing styrene dispersed in microemulsions display larger particle diameter in case of isopropanol, owing to partial swelling.