Abstract: Anionic polymerization process for preparing impact-modified polystyrene, by 1) preparing a rubber solution from diene monomers or from diene monomers and styrene monomers by anionic solution polymerization, using an organyllithium compound, 2) adding sufficient organylaluminum compound to give an Al/Li molar ratio >1 (or in the case of dialkylaluminum phenolates >0.5), 3) adding styrene monomer, and 4) adding sufficient organyllithium compound, or organyllithium compound and organylaluminum compound, to make the Al/Li molar ratio <1 (or in the case of dialkylaluminum phenolates <0.5) ist, and polymerizing the mixture.