Abstract: An improved process for preparing high solids predominantly styrene-butadiene copolymer aqueous emulsions is disclosed which process comprises pre-emulsifying a portion of the monomers to be used in forming the copolymer and adding the resulting pre-emulsion to a mixture of the remainder of the monomers, all maintained at an aqueous solids content between about 50 and 75 weight percent, utilizing as initiators about 0.1 to about 2.0 percent, by weight, based upon the total monomer weight, of a lypophillic initiator and about 0.01 to about 0.2 percent, by weight on the same basis, of a hydrophillic initiator.