The nucleation process in the emulsion polymerizations of styrene, methyl methacrylate, and vinyl acetate stabilized by sodium dodecyl sulfopropyl maleate, a polymerizable surfactant (surfmer), was investigated. A nonpolymerizable surfactant, sodium dodecyl sulfate (SDS), was used as a reference. The results obtained suggested that the presence of the surfmer did not affect the nucleation mechanism (which seems to be micellar for styrene and homogeneous for MMA and VAc). The type of surfactant did not affect the dependence of the number of particles upon surfactant concentration for styrene, but the dependence for the surfmer was lower than that for SDS in the cases of MMA and VAc. This was interpreted in terms of formation of water-soluble oligomers that do not participate in the stabilization of the polymer particles.