Process for the preparation of pesticide-comprising aqueous polymer dispersions with an average particle size of the dispersed particles of <1000 nm by radical polymerization of an oil-in-water emulsion, the oil phase of which comprises at least one pesticide in at least one ethylenically unsaturated monomer, a solution of at least one pesticide in at least one monomer being emulsified in water in the presence of at least one surface-active agent to give a miniemulsion with an average particle size <500 nm and/or at least one pesticide being added during the emulsification or subsequently and the miniemulsion subsequently being polymerized under radical conditions, and the use of the dispersions which can thus be obtained for combating harmful microorganisms and/or for regulating the growth of plants and/or for combating undesirable plant growth and/or for combating undesirable insect or acarid infestation on plants and/or for combating phytopathogenic fungi and/or for seed treatment.