Abstract: Crosslinked addition polymer microparticles are produced by dispersion polymerization of monomers in an aliphatic hydrocarbon liquid in the presence of a dispersion stabilizer and also of a specified type of amino resin which is insoluble in the hydrocarbon liquid, at least one of the monomers polymerized carrying a group which can react with the amino resin under the conditions of polymerization. Coating compositions having improved application characteristics and/or giving improved film properties are obtained by dispersing the microparticles in combinations of suitable film-forming polymers and diluents.