The invention relates to the use of water-insoluble organopolysiloxane derivatives of the general formula (I)in which the radicalsR1 are alkyl radicals, preferably having 1 to 4 carbon atoms or aryl radicals, but at least 80% of the radicals R1 are methyl radicals, andR2 at least once in the molecule has the definition (a)for defoaming aqueous media, especially printing inks and paints.