Abstract: Organic compounds containing —CH2—CHR—O— and/or —CH2—CH(OH)— groupings (R=H, C1-C4-alkyl) produce, under the action of free radicals, small amounts of C1-C2-aldehydes, the content of which can be reduced to <1 ppm according to the novel process by adding compounds which can react with the aldehyde groups. The materials containing said groupings include many emulsifiers and protective colloids used in polymer chemistry, such as polyethylene glycols, polyvinyl alcohols or ethoxylation products of long-chain alcohols, phenols or amines. The process is of particular importance for the treatment of polymer dispersions which have been prepared by free-radical polymerization of monomers in the presence of such emulsifiers or protective colloids, and permits the preparation of aldehyde-free polymer dispersions and their use for sanitary and hygiene articles.