An aqueous polymer dispersion with an average particle size of less than 1000 nm comprising a) a polymer carrier prepared by heterophase radical polymerization of at least one ethyleni- cally unsaturated monomer in the presence of b) an oil-soluble organic UV absorber selected from the class of p-aminobenzoic acid derivatives; salicylic acid derivatives; benzophenone derivatives; diphenyl acrylate derivatives; benzofuran derivatives; polymeric UV absorbers, comprising one or more organosilicon radicals; cinnamic acid derivatives; camphor derivatives; s-triazine derivatives; trianilino-striazine derivatives; menthyl anthranilates; and benzotriazole derivatives; wherein the weight ratio of the oil-soluble organic UV absorber (b) to polymer carrier (a) is greater than 50 parts UV absorber per 100 parts of carrier; and c) a surfactant selected from c1) a nonionic surfactant selected from c11) the condensation product of a C6 to C18 fatty alcohol or C6 to C18 fatty acid and a mono- or disaccharide; and c2) an anionic surfactant selected from c21) sulfosuccinates and sulfosuccinamates; c22) fatty alcoholates; and c23) mixtures of phosphoric acid esters and fatty alcohols having from 6 to 18, preferably from 8 to 10, carbon atoms. The aqueous polymer dispersions show unexpectedly high sunscreen effects and a positive skin feeling. They have excellent anti-pollen, ant-dust and anti-oxidant performances in sun screen compositions.L'invention concerne une dispersion polymère aqueuse ayant une taille moyenne de particule inférieure à 1 000 nm, comprenant a) un support polymère préparé par polymérisation radicalaire en hétérophase d'au moins un monomère éthyléniquement insaturé en présence de b) un absorbeur UV organique soluble dans l'huile choisi dans la classe des dérivés de l'acide p-aminobenzoïque ; des dérivés de l'acide salicylique ; des dérivés de la benzophénone ; des dérivés du diphénylacrylate ; des dérivés du benzofurane ; des absorbeurs UV polymères, comprenant un