Abstract: Method of preparing a stable latex having two substantially monodisperse populations of vinyl chloride polymer particles, which method comprises polymerizing, in aqueous emulsion, vinyl-polymerizable monomers containing at least 60% by weight vinyl chloride, in the presence of bothA. a vinyl chloride polymer seed latex providing between about 0.5 and 20% of dry solids based on total weight of said monomers, having particles of mean diameter between about 0.15 and 0.6 microns and having a "first" surfactant in amount corresponding to a seed-particle surface coverage of from 5% to 100%, andB. a "second" surfactant of different chemical type in amount corresponding to from about 0.01% to 2% by weight of total monomer,Wherein the chemical type of each surfactant is nonionic or carboxylate or sulfonate or sulfate or sulfosuccinate, but wherein the chemical type of the "second" surfactant is different from the chemical type of the "first" surfactant.