Abstract: A process for the continuous preparation of ABS polymers by free-radical-initiated polymerization of, in particular, styrene and acrylonitrile in the presence of polybutadiene, in the presence or absence of a solvent, in a reactor cascade comprising at least 3 stirred reactors operating essentially without back-mixing, at least some of which contain internal cooling tubes for dissipating the heat of polymerization, at from 50 to 180.degree. C., phase inversion taking place in one of the reactors which contains means for generating a high shear force, and an apparatus for carrying out the process comprising an essentially cylindrical/tubular vessel jacket and a cylindrical internal element connected to a stirrer shaft by rotational force and having an external diameter which is slightly less than the internal diameter of the vessel jacket.