An early transition metal metallocene compound, Cp2ZrCl2, with an anionic surfactant, sodium n-dodecyl sulfate (SDS) as emulsifier and NaBPh4 as cocatalyst has been found to be an effective catalytic system for polymerization and copolymerization of monomers like styrene and methyl methacrylate in aqueous medium. The diameters of the latex particles were found to be in between 20 and 40 nm. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 3920-3927, 2011