Polycarbonate/graft ABS blends with improved weld line strength

A thermoplastic polymer blend composition consisting essentially of (a) from about 5 to about 30 weight percent of a graft copolymer component comprising from about 50 to about 60 weight percent of a diene rubber substrate and a grafted portion formed from a monovinyl aromatic monomer and an alkenyl nitrile monomer, the graft copolymer containing less than about 5 weight percent methyl methacrylate, (b) from about 12 to about 20 weight percent of a polymethylmethacrylate homopolymer or a copolymer thereof with C.sub.1 -C.sub.4 alkyl acrylates, and (c) from about 65 to about 95 weight percent of a polycarbonate component.