Abstract: The average particle size of latices of polymers prepared by aqueous emulsion polymerization of ethylenically unsaturated and/or diolefinic monomers is increased markedly by admixture therewith of polyethoxylated surfactants having an HLB Value of 16-19.5 which are based on either long chain alkyl amines and/or esters of aliphatic polyols and fatty acids.This invention relates to a process for enlarging or agglomerating, i.e. coarsening irreversibly, the particles contained in a polymer dispersion. In particular, the invention is concerned with polymer dispersions obtained by emulsion polymerization of ethylenically unsaturated or polyunsaturated monomers.Preferred polymer dispersions (latex polymers) for which the method of the invention can best be used are the water immiscible emulsion homopolymers and copolymers of C.sub.4.sub.-6 conjugated diolefins such as butadiene, isoprene, chloroprene, 2,3-dimethyl-butadiene and 2-methyl-butadiene.