Moulding compositions based on ABS-graft polymers, containing:A. 5 to 70 parts, by weight of a graft polymer obtained by grafting 20 to 60 parts by weight of a mixture of styrene and acrylonitrile in a ratio, by weight, of 95 : 5 to 60 : 40 onto 80 to 40 parts, by weight, of polybutadiene or a butadiene copolymer with a butadiene content of > 30% with an average particle diameter of 0.26 to 0.65 .mu. and a grafting degree of 0.15 to 0.7;B. 0 to 50 parts, by weight, of a graft polymer obtained by polymerizing 40 to 60 parts, by weight, of a mixture of styrene and acrylonitrile in a ratio, by weight, of 95 : 5 to 60 : 40 onto 60 to 40 parts, by weight, of polybutadiene or a butadiene copolymer with a butadiene content of more than 30%, with an average particle diameter of from 0.05 to 0.25 .mu. and a grafting degree of 0.4 to 0.9; andC. 25 to 95 parts, by weight, of a copolymer of styrene and/or .alpha.-methyl styrene on the one hand and acrylonitrile on the other hand in a ratio by weight, of 80 : 20 to 60 : 40 with an average molecular weight M.sub.w (weight average) of from 50,000 to 200,000 and a molecular heterogeneity U of 4.5 to 1.0; such thatD. the ratios, by weight, of styrene (including .alpha.-methyl styrene if present) to acrylonitrile satisfy the following conditions: ##EQU1##