Abstract: The invention relates to a silicon dioxide dispersion that comprises a) an outer flowable phase containing 1) polymerizable monomers, oligomers and/or prepolymers that can be converted to polymers by non-radical reaction; and/or 2) polymers, and b) a disperse phase containing amorphous silicon dioxide. The inventive dispersion is characterized in that the average particle size dmax of the silicon dioxide as measured by small angle neutron scattering (SANS) is between 3 and 50 nm at a maximum half-width of the distribution curve of 1.5 dmax. Such a silicon dioxide dispersion can be easily manufactured even at higher concentrations of the disperse phase and can be used to produce polymer materials that have advantageous properties, especially advantageous mechanical properties.