The dispersion polymerization of styrene in ethanol-water mixtures has been investigated. The reactions were carried out in the presence of maleate based poly(ethylene oxide) macromonomers as steric stabilizer precursors : R-MA-EO(n)-R’, with R = H or n-C12H25, MA = maleic acid, n = 34, 42, and 49, and R’ = H or CH3. Nearly monodisperse polystyrene particles from 900 to 2000 nm in diameter were obtained. The structure and the concentration of the macromonomer, and the polarity of the solvent, affect the particle size and the particle size distribution. The location of the macromonomer, its conversion, and its incorporation yield in the particles throughout the entire polymerization are discussed. Maleate macromonomers react quickly to yield very low molecular weight styrene copolymers. Some of the copolymers take part in the stabilization of the particles as weakly adsorbed species. Hydrophilic macromonomers are well suited for dispersion polymerization, but the incorporation of these macromonomers into the polymer particles is not improved if they have an amphiphilic structure.