Abstract: Impact modifiers that produce transparent, high Dynatup impact strength blends with amorphous, aromatic polyesters are described. The impact modifiers are core-shell polymers with (A) a core composed principally of rubbery polymers, such as copolymers of diolefins with vinyl aromatic monomers, such as copolymers of butadiene with styrene, (B) an intermediate stage composed principally of hard polymers, such as polymers or copolymers of vinyl aromatic monomers, and (C) a shell composed principally of vinyl aromatic copolymers that contain hydroxyl functional groups or their equivalents (e.g. styrene/hydroxyalkyl (meth)acrylate copolymers).