Abstract: An emulsion polymer comprising as one of its components a graft copolymer of a residual aromatic monomer-free support resin polymer and a vinyl chloride (co)polymer is disclosed. The emulsion polymer is prepared using a two-stage process. In the first stage, a chasing monomer is reacted in the presence of a support resin polymer having at least one aromatic monomer to form an polymer which is free of residual monomer and has monomeric units derived from the aromatic monomer(s). In a second stage, the vinyl chloride emulsion (co)polymer is made in situ in a reaction mixture comprising the polymer which is free of residual monomer. An extensive grafting at the second stage yields a novel water dispersible graft copolymer containing both styrene and vinyl chloride.