The invention relates to thermoplastic moulding materials containing A) between 20 and 97 wt. % of a thermoplastic polyester; B) between 1 and 40 wt. % of a phosphinic acid salt and/or a diphosphinic acid salt and/or the polymers thereof, constituent B) having an average particle size (value d50) which is smaller than 10 μm; C) between 1 and 30 wt. % of a nitrogenated flameproofing agent; D) between 0 and 5 wt. % of at least one ester or amide of saturated or unsaturated aliphatic carboxylic acids having between 10 and 40 C atoms and aliphatic saturated alcohols or amines having between 2 and 40 C atoms; and E) between 0 and 60 wt. % of other additives. The total weight percent of constituents A) to E) amounts to 100%.